-- [ʞ] parvan.lua
--  ? tool for maintaining and searching dictionaries
-- [ CONTROL CLASS: GREEN ]
-- [ CODEWORDS: - GENERAL ACCESS - ]
-- [ CONTROLLING AUTHORITY: - INTERDIRECTORIAL -
--  < Commission for Defense Communication >
--    +WCO   Worlds Culture Overdirectorate
--      SSD  Social Sciences Directorate
--       ELS External Linguistics Subdirectorate
--    +WSO   Worlds Security Overdirectorate
--      EID  External Influence Directorate ]

local function implies(a,b) return a==b or not(a) end

local function map(lst,fn)
	local new = {}
	for k,v in pairs(lst) do
		local nv, nk = fn(v,k)
		new[nk or k] = nv
	end
	return new
end
local function mapD(lst,fn) --destructive
	-- WARNING: this will not work if nk names an existing key!
	for k,v in pairs(lst) do
		local nv, nk = fn(v,k)
		if nk == nil or k == nk then
			lst[k] = nv
		else
			lst[k] = nil
			lst[nk] = nv
		end
	end
	return lst
end
local function pushi(dest, idx, src, ...)
	if not src then return end
	dest[idx] = src
	pushi(dest, idx+1, ...)
end
local function push(dest, ...) pushi(dest,#dest+1,...) end
local function cons(car, cdr)
	local new = {car}
	for k,v in ipairs(cdr) do new[k+1] = v end
	return new
end
local function tcatD(dest, ...)
	local i = #dest
	local function iter(src, ...)
		if src == nil then return end
		local sc = #src
		for j=1,sc do dest[i+j] = src[j] end
		i = i + sc
		iter(...)
	end
	iter(...)
end
local function fastDelete(table,idx)
-- delete without preserving table order
	local l = #table
	table[idx] = table[l]
	table[l] = nil
	return table
end
local function tcat(...)
	local new = {}
	tcatD(new, ...)
	return new
end
local ansi = {
	levels = {
		plain = 0;
		ansi = 1;
		color = 2;
		color8b = 3;
		color24b = 4;
	};
}

ansi.seqs = {
	br = {ansi.levels.ansi, "[1m", "[22m"};
	hl = {ansi.levels.ansi, "[7m", "[27m"};
	ul = {ansi.levels.ansi, "[4m", "[24m"};
	em = {ansi.levels.ansi, "[3m", "[23m"};
};

function ansi.termclass(fd) -- awkwardly emulate isatty
	if fd:seek('cur',0) then
		return ansi.levels.plain
	end

	if os.getenv('COLORTERM') == 'truecolor' then
		return ansi.levels.color24b
	end

	local term = os.getenv('TERM')
	if term then
		if term:match '-256color' then
			return ansi.levels.color8b
		elseif term:match '-color' then
			return ansi.levels.color
		else
			return ansi.levels.ansi
		end
	end

	return ansi.levels.plain
end

function ansi.formatter(fd)
	local cl = ansi.termclass(fd)
	local id = function(...) return ... end
	local esc = '\27'
	local f = {}
	for k,v in pairs(ansi.seqs) do
		local lvl, on, off = table.unpack(v)
		if lvl <= cl then
			f[k] = function(s)
				return esc..on .. s .. esc..off
			end
		else f[k] = id end
	end
	local function ftoi(r,g,b)
		return math.ceil(r*0xff),
		       math.ceil(g*0xff),
		       math.ceil(b*0xff)
	end
	local reset = "\27[39m"
	function f.color(str, n, br)
		return string.format("\27[%s%cm",
			(bg and 4 or 3) +
			(br and 6 or 0), 0x30+n)
			.. str .. reset
	end
	function f.resetLine()
		return '\27[1K\13'
	end
	if cl == ansi.levels.color24b then
		function f.rgb(str, r,g,b, bg)
			return string.format("\27[%c8;2;%u;%u;%um", bg and 0x34 or 0x33,
				ftoi(r,g,b)) .. str .. reset
		end
	elseif cl == ansi.levels.color8b then
		function f.rgb(str, r,g,b, bg)
			local code = 16 + math.floor(r * 5)*36 + math.floor(g * 5)*6 + math.floor(b * 6)
			return string.format("\27[%c8;5;%um", bg and 0x34 or 0x33, code)
				.. str .. reset
		end
	elseif cl == ansi.levels.color then
		function f.rgb(str, r,g,b, bg)
			local code = 0x30 + 1 -- TODO
			return string.format("\27[%c%cm", bg and 0x34 or 0x33, code)
				.. str .. reset
		end
	else
		function f.rgb(s) return s end
		function f.color(s) return s end
		function f.resetLine() return '' end
	end
	return f
end


local function dump(v,pfx,cyc,ismeta)
	pfx = pfx or ''
	cyc = cyc or {}
	local np = pfx .. '   '

	if type(v) == 'table' then
		if cyc[v] then return '<...>' else cyc[v] = true end
	end

	if type(v) == 'string' then
		return string.format('%q', v)
	elseif type(v) == 'table' then
		local str = ''
		for k,v in pairs(v) do
			local tkey, tval = dump(k,np,cyc), dump(v,np,cyc)
			str = str .. string.format('%s[%s] = %s\n', np, tkey,tval)
		end
		local meta = ''
		if getmetatable(v) then
			meta = dump(getmetatable(v),pfx,cyc,true) .. '::'
		end
		if ismeta then
			return string.format('%s<|\n%s%s|>',meta,str,pfx)
		else
			return meta..'{\n' .. str .. pfx .. '}'
		end
	else
		return string.format('%s', v)
	end
end

local struct = {
	__call = function(s,...) return s:mk(...) end;
}
function struct:mk(s)
	function s.is(o) return getmetatable(o) == s end
	return setmetatable(s, self)
end
setmetatable(struct, struct)

local stream = struct {
	__index = {
		next = function(self, f)
			local flds = {string.unpack('<'..f, self.data, self.index)}
			self.index = flds[#flds]
			flds[#flds] = nil
			return table.unpack(flds)
		end;
	};
	mk = function(self, str)
		return setmetatable({
			data = str;
			index = 1;
		}, self)
	end;
}

local fmt = {}

local userError = struct {
	__tostring = function(self) return self.msg end;
	mk = function(self, s) return setmetatable({msg=s},self) end;
}

local function id10t(...)
	error(userError(string.format(...)),0)
end

local packer,unpacker =
	function(f) return function(...) return string.pack  ("<"..f, ...) end end,
	function(f) return function( s ) return s:next       (f) end end
local qpack = function(f) return {
	encode = packer(f);
	decode = unpacker(f);
} end

local parse, marshal
fmt.string = qpack "s4"
fmt.label = qpack "s2"
fmt.tag = qpack "s1"
fmt.u8 = qpack "I1"
fmt.u16 = qpack "I2"
fmt.u24 = qpack "I3"
fmt.u32 = qpack "I4"
fmt.path = {
	-- encodes a FIXED path to an arbitrary type of object
	encode = function(a)
		local kind = 0
		local vals = {}
		if a.w then kind = 1
			table.insert(vals, marshal(fmt.label, a.w))
			if a.dn then kind = 2
				table.insert(vals, marshal(fmt.u8, a.dn))
				if a.mn then kind = 3
					table.insert(vals, marshal(fmt.u8, a.mn))
					if a.nn then kind = 4
						table.insert(vals, marshal(fmt.u8, a.nn))
					end
				end
			end
		end
		return marshal(fmt.u8,kind) .. table.concat(vals)
	end;
	decode = function(s)
		local kind <const> = parse(fmt.u8, s)
		local path = {}
		local components <const> = {
			{'w',fmt.label};
			{'dn',fmt.u8};
			{'mn',fmt.u8};
			{'nn',fmt.u8};
		}
		for i=1,kind do
			local label, ty = table.unpack(components[i])
			path[label] = parse(ty,s)
		end
		return path
	end;
}
fmt.list = function(t,ty) ty = ty or fmt.u32
	return {
		encode = function(a)
			local vals = {marshal(ty, #a)}
			for i=1,#a do
				table.insert(vals, marshal(t, a[i]))
			end
			return table.concat(vals)
		end;
		decode = function(s)
			local n = parse(ty, s)
			local vals = {}
			for i=1,n do
				table.insert(vals, parse(t, s))
			end
			return vals
		end;
	}
end

fmt.map = function(from,to,ity)
	local ent = fmt.list({
		{'key', from},
		{'val', to}
	}, ity)
	return {
		encode = function(a)
			local m = {}
			for k,v in pairs(a) do
				table.insert(m, {key=k, val=v})
			end
			return ent.encode(m)
		end;
		decode = function(s)
			local lst = ent.decode(s)
			local m = {}
			for _,p in pairs(lst) do m[p.key] = p.val end
			return m
		end;
	}
end

fmt.enum = function(...)
	local vals,rmap = {...},{}
	for k,v in pairs(vals) do rmap[v] = k-1 end
	local ty = fmt.u8
	if #vals > 0xffff then ty = fmt.u32 -- just in pathological case
	elseif #vals > 0xff then ty = fmt.u16 end
	return {
		encode = function(a)
			if not rmap[a] then error(string.format('"%s" is not part of enum "%s"', a, table.concat(vals,'","')),3) end
			return marshal(ty, rmap[a])
		end;
		decode = function(s)
			local n = parse(ty,s)
			if (n+1) > #vals then error(string.format('enum "%s" does not have %u members', table.concat(vals,'","'),n),3) end
			return vals[n+1]
		end;
	}
end

fmt.uid = fmt.u32

fmt.relatable = function(ty)
	return tcat(ty,{
		{'rels',fmt.list(fmt.uid,fmt.u16)};
	})
end

fmt.note = {
	{'kind', fmt.tag};
	{'paras', fmt.list(fmt.string)};
}

fmt.example = {
	{'quote',fmt.string};
	{'src',fmt.label};
}

fmt.meaning = fmt.relatable {
	{'lit', fmt.string};
	{'examples', fmt.list(fmt.example,fmt.u8)};
	{'notes', fmt.list(fmt.note,fmt.u8)};
}

fmt.phrase = fmt.relatable {
	{'str',fmt.label};
	{'means',fmt.list(fmt.meaning,fmt.u8)};
}

fmt.def = fmt.relatable {
	{'part', fmt.u8};
	{'branch', fmt.list(fmt.label,fmt.u8)};
	{'means', fmt.list(fmt.meaning,fmt.u8)};
	{'forms', fmt.map(fmt.u16,fmt.label,fmt.u16)};
	{'phrases', fmt.list(fmt.phrase,fmt.u16)};
}

fmt.word = fmt.relatable {
	{'defs', fmt.list(fmt.def,fmt.u8)};
}

fmt.dictHeader = {
	{'lang', fmt.tag};
	{'meta', fmt.string};
	{'partsOfSpeech', fmt.list(fmt.tag,fmt.u16)};
	{'inflectionForms', fmt.list({
		{'name', fmt.tag};
		{'abbrev', fmt.tag};
		{'desc', fmt.string};
		{'parts', fmt.list(fmt.tag,fmt.u8)};
		-- which parts of speech does this form apply to?
		-- leave empty if not relevant
	},fmt.u16)};
}

fmt.relSet = {
	{'uid', fmt.uid};
		-- IDs are persistent random values so they can be used
		-- as reliable identifiers even when merging exports in
		-- a parvan-unaware VCS
	{'kind', fmt.enum('syn','ant','met')};
	-- membership is stored in individual objects, using a field
	-- attached by the 'relatable' template
}

fmt.dict = {
	{'header', fmt.dictHeader};
	{'words', fmt.map(fmt.string,fmt.word)};
	{'relsets', fmt.list(fmt.relSet)};
}

function marshal(ty, val)
	if ty.encode then
		return ty.encode(val)
	end
	local ac = {}

	for idx,fld in ipairs(ty) do
		local name, fty = table.unpack(fld)
		table.insert(ac, marshal(fty,
			assert(val[name],
				string.format('marshalling error: missing field %s', name)
			)
		))
	end

	return table.concat(ac)
end

function parse(ty, stream)
	if ty.decode then
		return ty.decode(stream)
	end

	local obj = {}
	for idx,fld in ipairs(ty) do
		local name, fty = table.unpack(fld)
		obj[name] = parse(fty, stream)
	end
	return obj
end

local function
atomizer()
	local map = {}
	local i = 1
	return function(v)
		if map[v] then return map[v] else
			map[v] = i
			i=i+1
			return i-1
		end
	end, map
end

local function rebuildRelationCache(d)
-- (re)build a dictionary's relation cache; needed
-- at load time and whenever any changes to relsets
-- are made (unless they're simple enough to update
-- the cache directly by hand, but that's very eeeh)
	local setMems = {} -- indexed by set id
	local function scan(obj,path)
		for _,v in pairs(obj.rels) do
			setMems[v] = setMems[v] or {mems={}}
			table.insert(setMems[v].mems, {path=path, obj=obj})
		end
	end
	for wk,wv in pairs(d.words) do
		scan(wv, {w=wk})
		for dk,dv in pairs(wv.defs) do
			scan(dv, {w=wk, dn=dk})
			for mk,mv in pairs(dv.means) do
				scan(mv, {w=wk, dn=dk, mn=mk})
			end
			for pk,pv in pairs(dv.phrases) do
				scan(pv, {w=wk, dn=dk, pn=pk})
				for mk,mv in pairs(pv.means) do
					scan(mv, {w=wk, dn=dk, pn=pk, mn=mk})
				end
			end
		end
	end
	for sk,sv in pairs(d.relsets) do
		setMems[sv.uid] = setMems[sv.uid] or {}
		setMems[sv.uid].set = sv
	end
	d._relCache = setMems
end

local function
writeDict(d)
	local atomizePoS, posMap = atomizer()
	for lit,w in pairs(d.words) do
		for j,def in ipairs(w.defs) do
			def.part = atomizePoS(def.part)
		end
	end
	d.header.partsOfSpeech = {}
	for v,i in pairs(posMap) do
		d.header.partsOfSpeech[i] = v
	end
	return 'PV0\2'..marshal(fmt.dict, d)
end

local function
readDict(file)
	local s = stream(file)
	local magic = s:next 'c4'
	if magic ~= 'PV0\2' then
		id10t 'not a parvan file'
	end
	local d = parse(fmt.dict, s)
	-- handle atoms
	for lit,w in pairs(d.words) do
		for j,def in ipairs(w.defs) do
			def.part = d.header.partsOfSpeech[def.part]
		end
	end

	-- create cachemaps for complex data structures to
	-- enable faster lookup that would otherwise require
	-- expensive scans
	rebuildRelationCache(d)
	return d
end


local function strwords(str) -- here be dragons
	local wds = {}
	local w = {}
	local state, d, quo, dquo = 0,0
	local function flush(n,final)
		if next(w) or state ~= 0 and state < 10 then
			table.insert(wds, utf8.char(table.unpack(w)))
			w = {}
		elseif final and state > 10 then
			table.insert(wds, '\\')
		end
		state = n
		quo = nil
		dquo = nil
		d = 0
	end
	local function isws(c)
		return c == 0x20 or c == 0x09 or c == 0x0a
	end
	for p,cp in utf8.codes(str) do
		if state == 0 then -- begin
			if not(isws(cp)) then
				if cp == 0x22 or cp == 0x27 then
					quo = cp
				elseif cp == 0x5b then -- boxquote
					 quo = 0x5d
					dquo = 0x5b
				elseif cp == 0x7b then -- curlquote
					 quo = 0x7d
					dquo = 0x7b
				elseif cp == 0x201c then -- fancyquote
					 quo = 0x201d
					dquo = 0x201c
				end
				if quo then
					state = 2
					d = 1
				elseif cp == 0x5c then -- escape
					state = 11
				else
					state = 1
					table.insert(w, cp)
				end
			end
		elseif state == 1 then -- word
			if isws(cp) then flush(0)
			elseif cp == 0x5c then state = 11 else
				table.insert(w,cp)
			end
		elseif state == 2 then -- (nested?) quote
			if cp == 0x5c then state = 12
			elseif cp == quo then
				d = d - 1
				if d == 0 then
					flush(0)
				else
					table.insert(w,cp)
				end
			else
				if cp == dquo then d = d + 1 end
				table.insert(w,cp)
			end
		elseif state == 11 or state == 12 then -- escape
			-- 12 = quote escape, 11 = raw escape
			if cp == 0x63 then --n
				table.insert(w,0x0a)
			else
				table.insert(w,cp)
			end
			state = state - 10
		end
	end
	flush(nil,true)
	return wds
end

local predicates
local function parsefilter(str)
	local f = strwords(str)
	if #f == 1 then return function(e) return predicates.lit.fn(e,f[1]) end end
	if not predicates[f[1]] then
		id10t('no such predicate %s',f[1])
	else
		local p = predicates[f[1]].fn
		return function(e)
			return p(e, table.unpack(f,2))
		end
	end
end

do
	local function p_all(e,pred,...)
		if pred == nil then return true end
		pred = parsefilter(pred)
		if not pred(e) then return false end
		return p_all(e,...)
	end;
	local function p_any(e,pred,...)
		if pred == nil then return false end
		pred = parsefilter(pred)
		if pred(e) then return true end
		return p_any(e,...)
	end;
	local function p_none(e,pred,...)
		if pred == nil then return true end
		pred = parsefilter(pred)
		if pred(e) then return false end
		return p_none(e,...)
	end;
	local function p_some(e,count,pred,...)
		if count == 0 then return true end
		if pred == nil then return false end
		pred = parsefilter(pred)
		if pred(e) then
			count = count-1
		end
		return p_some(e,count,...)
	end;

	local function prepScan(...)
		local map = {}
		local tgt = select('#',...)
		for _,v in pairs{...} do map[v] = true end
		return map,tgt
	end
	predicates = {
		all = {
			fn = p_all;
			syntax = '<pred>…';
			help = 'every sub-<pred> matches'
		};
		any = {
			fn = p_any;
			syntax = '<pred>…';
			help = 'any sub-<pred> matches'
		};
		none = {
			fn = p_none;
			syntax = '<pred>…';
			help = 'no sub-<pred> matches'
		};
		some = {
			fn = p_some;
			syntax = '<count> <pred>…';
			help = '<count> or more sub-<pred>s match'
		};
		def = {
			help = 'word has at least one definition that contains all <keyword>s';
			syntax = '<keyword>…';
			fn = function(e,...)
				local kw = {...}
				for i,d in ipairs(e.word.defs) do
					for j,m in ipairs(d.means) do
						for k,n in ipairs(kw) do
							if not string.find(m.lit, n, 1, true) then
								goto notfound
							end
						end
						do return true end
						::notfound::
					end
				end
				return false
			end;
		};
		lit = {
			help = 'word is, begins with, or ends with <word>';
			syntax = '<word> [(pfx|sfx)]';
			fn = function(e,val,op)
				if not op then
					return e.lit == val
				elseif op == 'pfx' then
					return val == string.sub(e.lit,1,#val)
				elseif op == 'sfx' then
					return val == string.sub(e.lit,(#e.lit) - #val + 1)
				else
					id10t('[lit %s %s] is not a valid filter, “%s” should be either “pfx” or “sfx”',val,op,op)
				end
			end;
		};
		form = {
			help = 'match against word\'s inflected forms';
			syntax = '(<inflect> | <form> (set | is <inflect> | (pfx|sfx|match) <affix>))';
			fn = function(e, k, op, v)
			end;
		};
		part = {
			help = 'word has definitions for every <part> of speech';
			syntax = '<part>…';
			fn = function(e,...)
				local map, tgt = prepScan(...)
				local matches = 0
				for i,d in ipairs(e.word.defs) do
					if map[d.part] then matches = matches + 1 end
				end
				return matches == tgt
			end
		};
		root = {
			help = 'match a word that derives from every <word>';
			syntax = '<word>…';
			fn = function(e,...)
				local map, tgt = prepScan(...)
				for i,d in ipairs(e.word.defs) do
					local matches = 0
					for j,r in ipairs(d.branch) do
						if map[r] then matches = matches + 1 end
					end
					if matches == tgt then return true end
				end
			end
		};
		note = {
			help = 'word has a matching note';
			syntax = '([kind <kind> [<term>]] | term <term> | (min|max|count) <n>)';
			fn = function(e, op, k, t)
				if op == 'kind' or op == 'term' then
					if op == 'term' and t then
						id10t('too many arguments for [note term <term>]')
					end
					for _,d in ipairs(e.word.defs) do
					for _,m in ipairs(d.means) do
					for _,n in ipairs(m.notes) do
						if op=='term' or n.kind == k then
							if op=='kind' and t == nil then return true end
							if string.find(table.concat(n.paras,'\n'), t or k, 1, true) ~= nil then return true end
						end
					end end end
				elseif op == 'min' or op == 'max' or op == 'count' then
					if t then
						id10t('too many arguments for [note %s <n>]',op)
					end
					local n = math.floor(tonumber(k))
					local total = 0
					for i,d in ipairs(e.word.defs) do
					for j,m in ipairs(d.means) do
						total = total + #m.notes
						if op == 'min' and total >= n then return true end
						if op == 'max' and total > n then return false end
					end end
					if op == 'count' then return total == n end
					if op == 'max'   then return total <= n end
					return false
				end
			end;
		};
	}
end

local function
safeopen(file,...)
	if type(file) == 'string' then
		local fd = io.open(file,...)
		if not fd then error(userError("cannot open file " .. file),2) end
		return fd
	else
		return file
	end
end

local function copy(tab)
	local new = {}
	for k,v in pairs(tab) do new[k] = v end
	return new
end

local function pathParse(p)
-- this is cursed, rewrite without regex pls TODO
	if p == '.' then return {} end
	local function comp(pfx)
		return pfx .. '([0-9]+)'
	end
	local function mtry(...)
		local mstr = '^(.+)'
		for _, v in ipairs{...} do
			mstr = mstr .. comp(v)
		end
		return p:match(mstr .. '$')
	end

	local xn
	local w,dn,pn,mn,nn = mtry('%.','/p','/m','/n')
	if not w then w,dn,pn,mn,xn = mtry('%.','/p','/m','/x') end
	if not w then w,dn,pn,mn = mtry('%.','/p','/m') end
	if not w then w,dn,pn= mtry('%.','/p') end
	if not w then
		local comps = {'%.','/m','/n'}
		for i=#comps, 1, -1 do
			local args = {table.unpack(comps,1,i)}
			w,dn,mn,nn = mtry(table.unpack(args))
			if not w and args[i] == '/n' then
				args[i] = '/x'
				w,dn,mn,xn = mtry(table.unpack(args))
			end
			if w then break end
		end
	end
	if not w then w=p:match('^(.-)%.?$') end
	return {w = w, dn = tonumber(dn), mn = tonumber(mn), pn=tonumber(pn); nn = tonumber(nn), xn = tonumber(xn)}
end
local function pathString(p,styler)
	local function s(s, st, ...)
		if styler then
			return styler[st](tostring(s),...)
		else return s end
	end

	local function comp(c,n,...)
		return s('/','color',5)
		    .. s(string.format("%s%u",c,n), 'color',...)
	end
	local t = {}
	if p.w then t[1] = s(p.w,'ul') else return '.' end
	if p.dn then t[2] = string.format(".%s", s(p.dn,'br')) end
	if p.pn then t[#t+1] = comp('p',p.pn,4,true) end
	if p.mn then t[#t+1] = comp('m',p.mn,5,true) end
	if p.xn then t[#t+1] = comp('x',p.xn,6,true)
	elseif p.nn then t[#t+1] = comp('n',p.nn,4) end
	if t[2] == nil then
		return p.w .. '.' --make sure paths are always valid
	end
	return s(table.concat(t),'em')
end
local function pathMatch(a,b)
	return a.w  == b.w
		and a.dn == b.dn
		and a.mn == b.mn
		and a.pn == b.pn
		and a.nn == b.nn
		and a.xn == b.xn
end
local function pathResolve(ctx, a)
	local res = {}

	if not a.w then return res end -- empty paths are valid!
	local function lookup(seg, tbl,val)
		if not tbl then error('bad table',2) end
		local v = tbl[val]
		if v then return v end
		id10t('bad %s in path: %s', seg, val)
	end

	res.word = lookup('word', ctx.dict.words, a.w)
	if not a.dn then return res end

	res.def = lookup('definition', res.word.defs, a.dn)
	if (not a.pn) and (not a.mn) then return res end

	local m if a.pn then
		res.phrase = lookup('phrase', res.def.phrases, a.pn)
		res.meaning = lookup('meaning', res.phrase.means, a.mn)
	else
		res.meaning = lookup('meaning', res.def.means, a.mn)
	end

	if a.xn then
		res.ex = lookup('example',res.meaning.examples,a.xn)
	elseif a.nn then
		res.note = lookup('note',res.meaning.notes,a.nn)
	end

	return res
end

local function pathNav(...)
	local t = pathResolve(...)
	return t.word,t.def,t.phrase,t.meaning,t.ex or t.note
end

local function pathRef(ctx, a)
	local w,d,p,m,n = pathNav(ctx,a)
	return n or m or p or d or w
end

local function pathSub(super,sub)
	if super.w == nil then return true end
	if sub.w ~= super.w then return false end

	if super.pn == nil then goto checkMN end
	if sub.pn ~= super.pn then return false end

	::checkMN::
	if super.mn == nil then return true end
	if sub.mn ~= super.mn then return false end

	if super.xn then
		if sub.nn then return false end
		if sub.xn ~= super.xn then return false end
	elseif super.nn then
		if sub.xn then return false end
		if sub.nn ~= super.nn then return false end
	end

	return true
end

local cmds = {
	create = {
		help = "initialize a new dictionary file";
		syntax = "<lang>";
		raw = true;
		exec = function(ctx, lang)
			if not lang then
				id10t 'for what language?'
			end
			local fd = safeopen(ctx.file,"wb")
			local new = {
				header = {
					lang = lang;
					meta = "";
					partsOfSpeech = {};
					inflectionForms = {};
				};
				words = {};
				relsets = {};
			}
			local o = writeDict(new);
			fd:write(o)
			fd:close()
		end;
	};
	coin = {
		help = "add a new word";
		syntax = "<word>";
		write = true;
		exec = function(ctx,word)
			if ctx.dict.words[word] then
				id10t "word already coined"
			end
			ctx.dict.words[word] = {defs={},rels={}}
		end;
	};
	def = {
		help = "define a word";
		syntax = "<word> <part-of-speech> [<meaning> [<root>…]]";
		write = true;
		exec = function(ctx,word,part,means,...)
			local etym = {...}
			if (not word) or not part then
				id10t 'bad definition'
			end
			if not ctx.dict.words[word] then
				ctx.dict.words[word] = {defs={},rels={}}
			end
			local n = #(ctx.dict.words[word].defs)+1
			ctx.dict.words[word].defs[n] = {
				part = part;
				branch = etym;
				means = {means and {
					lit=means;
					examples={};
					notes={};
					rels={};
				} or nil};
				forms = {};
				phrases = {};
				rels={};
			}
			ctx.log('info', string.format('added definition #%u to “%s”', n, word))
		end;
	};
	mean = {
		help = "add a meaning to a definition";
		syntax = "<word> <def#> <meaning>";
		write = true;
		exec = function(ctx,word,dn,m)
			local t = pathResolve(ctx,{w=word,dn=dn})
			table.insert(t.d.means, {lit=m,notes={}})
		end;
	};
	rel = {
		help = "manage groups of related words";
		syntax = {
			"(show|purge) <path> [<kind>]";
			"(link|drop) <word> <group#> <path>…";
			"new <rel> <path> <path>…";
			"destroy <word> [<group#>]";
			"rel ::= (syn|ant|co)"
		};
		write = true;
		exec = function(ctx, op, ...)
			local fo = ctx.sty[io.stdout]
			if op == nil  then id10t "not enough arguments" end
			local groups = {}
			if not (op=='new' or op=='link' or op=='drop' or op=='destroy' or op=='show' or op=='purge') then
				id10t('invalid operation “%s” for `rel`', op)
			end
			if op == 'new' then
				local rel = ...
				if rel ~= 'syn' and rel ~= 'ant' and rel ~= 'met' then
					id10t 'relationships must be synonymous, antonymous, or metonymous'
				end
				local links={}
				for i,l in ipairs{select(2,...)} do
					links[i] = pathParse(l)
				end
				local newstruct = {
					uid=math.random(1,0xffffFFFF);
					kind = rel;
				}
				table.insert(ctx.dict.relsets, newstruct)
				for _, m in pairs(links) do
					local obj = pathRef(ctx,m)
					table.insert(obj.rels,newstruct.uid)
				end

				rebuildRelationCache(ctx.dict)
			else -- assemble a list of groups
				local tgtw = ...
				local wp = pathParse(tgtw)
				local o = pathResolve(ctx, wp)

				for i,rs in pairs(ctx.dict.relsets) do
					local allMembers = ctx.dict._relCache[rs.uid].mems
					for j,s in ipairs(allMembers) do
						if pathSub(s.path, wp) then
							table.insert(groups, {
								set = {
									uid = rs.uid;
									kind = rs.kind;
									members = allMembers;
								};
								mem = s;
								id = i;
							})
							break
						end
					end
				end

				if op == 'show' then
					for i, g in ipairs(groups) do
						local w = pathResolve(ctx, {w=g.mem.w}).w
						local function label(path,w)
							local repr = path.w
							if path.dn then
								repr = repr .. string.format("(%s)", w.defs[path.dn].part)
								if path.mn then
									repr = repr .. string.format(": %u. %s", path.dn, w.defs[path.dn].means[path.mn].lit)
								else
									local fulldef = {}
									for i,v in ipairs(w.defs) do
										fulldef[i] = v.lit
									end
									repr = repr..table.concat(fulldef, '; ')
								end
							end

							return repr
						end

						local others = {}
						for j, oo in ipairs(g.set.members) do
							local o = oo.path
							local ow = pathResolve(ctx, {w=o.w}).w
							if (g.set.kind == 'ant' or not pathMatch(o, g.mem.path)) and
								--exclude antonym headwords
								not (g.set.kind == 'ant' and j==1) then
								table.insert(others, '      '..label(o,ow))
							end
						end
						local llab do
							local cdw = ctx.dict.words
							if g.set.kind == 'ant' then
								local ap = g.set.members[1].path
								llab = fo.br(label(ap,cdw[ap.w]) or '')
							else
								llab = fo.br(label(g.mem.path,cdw[g.mem.w]) or '')
							end
						end
						local kls = {
							syn = fo.color('synonyms',2,true)..' of';
							ant = fo.color('antonyms',1,true)..' of';
							met = fo.color('metonyms',4,true)..' of';
						}
						io.stdout:write(string.format("% 4u) %s\n%s", i, fo.ul(kls[g.set.kind] .. ' ' .. llab), table.concat(others,'\n')) .. '\n')
					end
					return false -- no changes made
				elseif op == 'link' or op == 'drop' then
					local tgtn, paths = (select(2,...)), { select(3, ...) }
					rebuildRelationCache(ctx.dict)
				elseif op == 'destroy' then
					local tgtw, tgtn = ...
					if not tgtn then id10t 'missing group number' end
					local delendum = groups[tonumber(tgtn)]
					if not delendum then id10t 'bad group number' end

					for k,v in pairs(delendum.set.members) do
						for idx, e in pairs(v.obj.rels) do
							if e == delendum.set.uid then
								fastDelete(v.obj.rels,idx)
							end
						end
					end
					fastDelete(ctx.dict.relsets, delendum.id)

					rebuildRelationCache(ctx.dict)
				else
					id10t 'invalid operation'
				end
			end
		end;
	};
	mod = {
		help = "move, merge, split, or delete words or definitions";
		syntax = {
			"<path> (drop | [move|merge|clobber] <path> | out [<part> [<root>…]])";
			"path ::= <word>[(@<def#>[/<meaning#>[:<note#>]]|.)]";
		};
		write = true;
	};
	note = {
		help = "add a note to a definition or a paragraph to a note";
		syntax = {"(<m-path> (add|for) <kind> | <m-path>:<note#>) <para>…";
			"m-path ::= <word>@<def#>/<meaning#>"};
		write = true;
		exec = function(ctx,path,...)
			local paras, mng
			local dest = pathParse(path)
			local t = pathResolve(ctx,path)
			if dest.nn then
				paras = {...}
			else
				local op, kind = ...
				paras = { select(3, ...) }
				if op == 'add' then
					dest.nn = #(t.m.notes) + 1
					t.m.notes[dest.nn] = {kind=kind, paras=paras}
					return
				elseif op == 'for' then
					for i,nn in ipairs(t.m.notes) do
						if nn.kind == kind then
							dest.nn = i break
						end
					end
					if not dest.nn then
						id10t('no note of kind %s in %s',kind,path)
					end
				end
			end
			local dpa = t.m.notes[dest.nn].paras
			local top = #dpa
			for i,p in ipairs(paras) do
				dpa[top+i] = p
			end
		end
	};
	shell = {
		help = "open an interactive prompt";
		raw = true;
	};
	help = {
		help = "show help";
		nofile = true;
		syntax = "[<command>]";
	};
	predicates = {
		help = "show available filter predicates";
		nofile = true;
		syntax = "[<predicate>]";
	};
	export = {
		help = "create a text file dump compatible with source control";
		syntax = "[<target-file>]";
	};
	import = {
		help = "generate a usable dictionary from a text export file";
		syntax = "[<input-file>]";
		raw = true;
		write = true;
	};
	dump = {
		exec = function(ctx) print(dump(ctx.dict)) end
	};
	ls = {
		help = "list all words that meet any given <filter>";
		syntax = {"[<filter>…]";
			"filter ::= (<word>|<pred> <arg>…)";
			"arg    ::= (<atom>|'['(<string>|<pred> <arg>…)']')"};
   }
}

function cmds.predicates.exec(ctx, pred)
	local list = predicates
	if pred then list = {predicates[pred]} end
	local f = ctx.sty[io.stderr]
	for k,p in pairs(predicates) do
		if p.help then
			io.stderr:write(
				f.br('  - ' ..
					f.rgb('[',1,0,.5) ..
					k .. ' ' ..
					(f.color(p.syntax,5) or '…') ..
					f.rgb(']',1,0,.5)) .. ': ' ..
				f.color(p.help,4,true) .. '\n')
		end
	end
end

function cmds.ls.exec(ctx,...)
	local filter = nil
	local out = {}
	for i,f in ipairs{...} do
		local fn = parsefilter(f)
		local of = filter or function() return false end
		filter = function(e)
			return fn(e) or of(e)
		end
	end
	for lit,w in pairs(ctx.dict.words) do
		local e = {lit=lit, word=w}
		if filter == nil or filter(e) then
			table.insert(out, e)
		end
	end
	table.sort(out, function(a,b) return a.lit < b.lit end)
	local fo = ctx.sty[io.stdout]

	local function gatherRelSets(path)
		local antonymSets, synonymSets, metonymSets = {},{},{}
		local obj = pathRef(ctx,path)
		if next(obj.rels) then
			for i, relid in ipairs(obj.rels) do
				local specuset,tgt,anto = {}
				local rel = ctx.dict._relCache[relid].set
				for j, mbr in ipairs(ctx.dict._relCache[relid].mems) do
					if pathMatch(mbr.path, path) then
						if     rel.kind == 'syn' then tgt = synonymSets
						elseif rel.kind == 'met' then tgt = metonymSets
						elseif rel.kind == 'ant' then
							if j == 1 -- is this the headword?
								then tgt = antonymSets
								else tgt = synonymSets
							end
						end
					elseif j == 1 and rel.kind == 'ant' then
						anto = mbr.path
					else
						table.insert(specuset, mbr.path)
					end
				end
				if tgt then
					table.insert(tgt, specuset)
					if anto then
						table.insert(antonymSets, {anto})
					end
				end
			end
		end
		local function flatten(lst)
			local new = {}
			for i, l in ipairs(lst) do tcatD(new, l) end
			return new
		end
		return {
			syn = flatten(synonymSets);
			ant = flatten(antonymSets);
			met = flatten(metonymSets);
		}
	end

	local function formatRels(rls, padlen)
		-- optimize for the common case
		if next(rls.syn) == nil and
		   next(rls.ant) == nil and
			next(rls.met) == nil then return {} end
		local pad = string.rep(' ',padlen)
		local function format(label, set)
			local each = map(set, function(e)
				local ew,ed = pathNav(ctx, e)
            local str = fo.ul(e.w)
				if ed then str = string.format('%s(%s)',str,ed.part) end
				if e.mn then str = string.format('%s§%u',str,e.mn) end
				return str
			end)
			return fo.em(string.format("%s%s %s",pad,label,table.concat(each,', ')))
		end
		local lines = {}
		local function add(l,c,lst)
			table.insert(lines, format(fo.color(l,c,true),lst))
		end
		if next(rls.syn) then add('synonyms:',2,rls.syn) end
		if next(rls.ant) then add('antonyms:',1,rls.ant) end
		if next(rls.met) then add('metonyms:',4,rls.met) end
		return lines
	end

	local function meanings(w,d,md,n)
		local start = md and 2 or 1
		local part = string.format('(%s)', d.part)
		local pad = md and string.rep(' ', #part) or ''
		local function note(n,insert)
			if not next(n.paras) then return end
			local pad = string.rep(' ',#(n.kind) + 9)
			insert('      ' .. fo.hl(' ' .. n.kind .. ' ') .. ' ' .. n.paras[1])
			for i=2,#n.paras do
				insert(pad..n.paras[2])
			end
		end
		local m = { (function()
			if d.means[1] then
				if md then
					local id = ''
					if ctx.flags.ident then
						id=' ['..pathString({w=w.lit,dn=n,mn=1}, fo)..']'
					end
					return string.format(" %s %s 1. %s", id, fo.em(part), d.means[1].lit)
				end
			else return
				fo.em(string.format('  %s [empty definition #%u]', part,n))
			end
		end)() }
		tcatD(m, formatRels(gatherRelSets{w=w.lit,dn=n,mn=1}, 6))
		for i=start,#d.means do local v = d.means[i]
			local id = ''
			if ctx.flags.ident then id='['..pathString({w=w.lit,dn=n,mn=n}, fo)..']' end
			table.insert(m, string.format('  %s%s %u. %s', pad, id, i, v.lit))
			tcatD(m, formatRels(gatherRelSets{w=w.lit,dn=n,mn=i}, 6))
			for j,n in ipairs(v.notes) do
				note(n, function(v) table.insert(m, v) end)
			end
		end
		return table.concat(m,'\n')
	end
	local function autobreak(str)
		if str ~= '' then return str..'\n' else return str end
	end
	for i, w in ipairs(out) do
		local d = fo.ul(fo.br(w.lit))
		local wordrels = autobreak(table.concat(
				formatRels(gatherRelSets{w=w.lit}, 2),
				'\n'
			))
		if #w.word.defs == 1 then
			d=d .. ' '
			    .. fo.rgb(fo.em('('..(w.word.defs[1].part)..')'),.8,.5,1) .. '\n'
			    .. meanings(w,w.word.defs[1],false,1) .. '\n'
			    .. autobreak(table.concat(formatRels(gatherRelSets{w=w.lit,dn=1}, 4), '\n'))
				 .. wordrels .. '\n'
		else
			for j, def in ipairs(w.word.defs) do
				local syn if wsc and wsc[j] then syn = wsc[j] end
				d=d .. '\n'
				    .. meanings(w,syn,def,true,j) .. '\n'
				    .. autobreak(table.concat(
						 formatRels(gatherRelSets{w=w.lit,dn=j}, 4),
						 '\n'
					 ))
			end
			d=d .. wordrels .. '\n'
		end
		io.stdout:write(d)
	end
end

function cmds.import.exec(ctx,file)
	local ifd = io.stdin
	if file then
		ifd = safeopen(file,'r')
	end

	local new = {
		header = {
			lang = lang;
			meta = "";
			partsOfSpeech = {};
			inflectionForms = {};
		};
		words = {};
		relsets = {};
	}

	local state = 0
	local relsets = {}
	local path = {}
	local inflmap, lastinfl = {}
	for l in ifd:lines() do
		local words = strwords(l)
		local c = words[1]
		local function syn(mn,mx)
			local nw = #words - 1
			if nw < mn or (mx ~= nil and nw > mx) then
				if mx ~= nil then
					id10t('command %s needs between %u~%u words',c,mn,mx)
				else
					id10t('command %s needs at least %u words',c,mn)
				end
			end
		end
		if c ~= '*' and c~='meta' then -- comments
			if state == 0 then
				if c ~= 'pv0' then
					id10t "not a parvan export"
				end
				new.header.lang = words[2]
				new.header.meta = words[3]
				state = 1
			else
				local T = pathResolve({dict=new}, path)
				local W,D,P,M,N,X =
					T.word,
					T.def,
					T.phrase,
					T.meaning,
					T.note,
					T.ex
				if c == 'w' then syn(1) state = 2
					path = {w=words[2]}
					new.words[words[2]] = {defs={},rels={}}
				elseif c == 'f' then syn(1)
					local nf = {
						name = words[2];
						abbrev = words[3] or "";
						desc = words[4] or "";
						parts = {};
					}
					table.insert(new.header.inflectionForms, nf)
					inflmap[words[2]] = #(new.header.inflectionForms)
					lastinfl = nf
				elseif c == 'fp' then syn(1)
					if not lastinfl then
						id10t 'fp can only be used after f' end
					table.insert(lastinfl.parts,words[2])
				elseif c == 's' then syn(2)
					relsets[words[3]] = relsets[words[3]] or {}
					relsets[words[3]].kind = words[2]
					relsets[words[3]].uid = tonumber(words[3])
					relsets[words[3]].members = relsets[words[3]].members or {}
				elseif state >= 2 and c == 'r' then syn(1)
					local rt
					if state == 2 then
						rt = W.rels
					elseif state == 3 then
						rt = D.rels
					elseif state == 4 then
						rt = D.rels
					elseif state == 14 then
						rt = P.rels
					end
					relsets[words[2]] = relsets[words[2]] or {
						uid = tonumber(words[2]) or math.random(0,0xffffFFFF);
						members={};
					}
					table.insert(relsets[words[2]].members, path)
				elseif state >= 2 and c == 'd' then syn(1) state = 3
					table.insert(W.defs, {
						part = words[2];
						branch = {};
						means = {};
						forms = {};
						phrases = {};
						rels = {};
					})
					path = {w = path.w, dn = #(W.defs)}
				elseif state >= 3 and c == 'dr' then syn(1)
					table.insert(D.branch, words[2])
				elseif state >= 3 and c == 'df' then syn(2)
					if not inflmap[words[2]] then
						id10t('no inflection form %s defined', words[2])
					end
					D.forms[inflmap[words[2]]] = words[3]
				elseif state >= 3 and c == 'p' then syn(1) state = 14
					table.insert(D.phrases, {
						str = words[2];
						means = {};
						rels = {};
					})
					path = {w = path.w, dn = path.dn, pn = #(D.phrases)}
				elseif state >= 3 and c == 'm' then syn(1) state = 4
					table.insert(D.means, {
						lit = words[2];
						notes = {};
						examples = {};
						rels = {};
					});
					path = {w = path.w, dn = path.dn, pn=path.pn, mn = #(D.means)}
				elseif state >= 4 and c == 'n' then syn(1) state = 5
					table.insert(M.notes, {kind=words[2], paras={}})
					path = {w = path.w, dn = path.dn, pn = path.pn, mn = path.mn, nn = #(M.notes)};
				elseif state >= 5 and c == 'np' then syn(1)
					table.insert(N.paras, words[2])
				end
				-- we ignore invalid ctls, for sake of forward-compat
			end
		end
	end

	for k,v in pairs(relsets) do
		if not v.uid then
			--handle non-numeric export ids
			v.uid = math.random(0,0xffffFFFF)
		end
		table.insert(new.relsets, v)

		for q,m in pairs(v.members) do
			table.insert(pathRef({dict=new},m).rels, v.uid)
		end
	end

	local ofd = safeopen(ctx.file,"w+b")
	local o = writeDict(new);
	ofd:write(o)
	ofd:close()
end

function cmds.export.exec(ctx,file)
	local ofd = io.stdout
	if file then ofd = safeopen(file, 'w+') end
	local function san(str)
		local d = 0
		local r = {}
		for i,cp in utf8.codes(str) do
			-- insert backslashes for characters that would
			-- disrupt strwords() parsing
			if cp == 0x0a then
				table.insert(r, 0x5c)
				table.insert(r, 0x6e)
			else
				if cp == 0x5b then
					d = d + 1
				elseif cp == 0x5d then
					if d >= 1 then
						d = d - 1
					else
						table.insert(r, 0x5c)
					end
				end
				table.insert(r, cp)
			end
		end
		return '[' .. utf8.char(table.unpack(r)) .. ']'
	end
	local function o(lvl,...)
		local pfx = ''
		if ctx.flags.human and lvl > 0 then
			pfx = string.rep('\t', lvl)
		end
		ofd:write(pfx..string.format(...)..'\n')
	end
	local d = ctx.dict
	o(0,'pv0 %s %s', san(d.header.lang), san(d.header.meta))
	local function checksyn(obj,lvl)
		for k,v in pairs(obj.rels) do
			o(lvl,'r %u',s.uid)
		end
	end
	for i,f in pairs(d.header.inflectionForms) do
		o(0,'f %s %s %s', san(f.name), san(f.abbrev), san(f.desc))
		for j,p in pairs(f.parts) do
			o(1,'fp %s', san(p))
		end
	end
	local function scanMeans(tbl,path,lvl)
		for j,m in ipairs(def.means) do
			o(lvl,'m %s', san(m.lit))
			local lp = copy(path)
			lp.mn = j
			checksyn(m,lp,lvl+1)
			for k,n in ipairs(m.notes) do
				o(lvl+1,'n %s', san(n.kind))
				for a,p in ipairs(n.paras) do
					o(lvl+2,'np %s', san(p))
				end
			end
		end
	end
	for lit, w in pairs(d.words) do
		o(0,'w %s',san(lit))
		checksyn(w,{w=lit},1)
		for i,def in ipairs(w.defs) do
			o(1,'d %s',san(def.part))
			checksyn(def,{w=lit,dn=i},2)
			for j,r in ipairs(def.branch) do
				o(2,'dr %s',san(r))
			end
			for j,p in ipairs(def.phrases) do
				o(2,'p %s',san(p.str))
				scanMeans(p.means, {w=lit,dn=i,pn=j}, 3)
			end
			scanMeans(def.means, {w=lit,dn=i}, 2)
		end
	end
	for _,s in ipairs(d.relsets) do o(0,'s %s %u', s.kind, s.uid) end
end

local function filterD(lst, fn)
-- cheap algorithm to destructively filter a list
-- DOES NOT preserve order!!
	local top = #lst
	for i=top,1,-1 do local m = lst[i]
		if not fn(m,i) then
			lst[i] = lst[top]
			lst[top] = nil
			top = top - 1
		end
	end
	return lst
end

function cmds.mod.exec(ctx, orig, oper, dest, ...)
	rebuildRelationCache(ctx.dict)
end

local function fileLegible(file)
	-- check if we can access the file
	local fd = io.open(file,"rb")
	local ret = false
	if fd then ret = true end
	fd:close()
	return ret
end


local function
prompt(p,multiline)
	-- returns string if successful, nil if EOF, false if ^C
	io.stderr:write(p)
	local ok, res = pcall(function()
	                      return io.stdin:read(multiline and 'a' or 'l')
	                     end)
	if ok then return res end
	return false
end

function cmds.shell.exec(ctx)
	if not fileLegible(ctx.file) then
		-- avoid accidentally creating a file without the
		-- proper document structure and metadata
		id10t("file %s must already exist and be at least readable", ctx.file)
	end

	local fd, rw = io.open(ctx.file,"r+b"), true
	if not fd then -- not writable
		ctx.log('warn',string.format('file %s is not writable', ctx.file))
		fd, rw = io.open(ctx.file, "rb"), false
	end
	ctx.fd = fd
	ctx.dict = readDict(fd:read 'a')
	fd:close()

	local written = false
	local fo = ctx.sty[io.stdout]
	local fe = ctx.sty[io.stderr]
	repeat
		local cmd = prompt(fe.br(string.format('(parvan %s) ', ctx.file)))
		if cmd == false then
			io.stderr:write(fe.resetLine())
			if written then
				ctx.log('warn', 'abandoning changes!')
			end
			return 0
		end
		if cmd and cmd ~= '' then
			local words = strwords(cmd)
			if next(words) then
				if words[1] == 'bail'    or
				   words[1] == 'abandon' or
				   words[1] == 'q!'     then
					if written then
						ctx.log('warn', 'abandoning changes!')
					end
					return 0
				end
				local c = cmds[words[1]]
				if c then
					if c.raw then
						ctx.log('fatal', words[1] .. ' cannot be run from `shell`')
					elseif not implies(c.write, rw) then
						ctx.log('fatal', ctx.file .. ' is not writable')
					else
						local ok, outcome = ctx.try(c.exec, ctx, table.unpack(words,2))
						if ok and outcome ~= false then written = written or c.write end
					end
				elseif cmd == 'save' or cmd == 'wq' then
					if not written then
						ctx.log('info', 'no changes to save')
					end
					cmd = nil
				elseif cmd == 'quit' or cmd == 'q' then
					if not written then cmd = nil else
						ctx.log('fatal', 'dictionary has unsaved changes')
					end
				else
					ctx.log('fatal', words[1] .. ' is not a command')
				end
			end
		end
	until cmd == nil

	if written then
		ctx.log('info', 'saving file')
		local out = writeDict(ctx.dict)
		local fd = io.open(ctx.file,'w+b')
		fd:write(out)
		fd:close()
	end
end

local function
showHelp(ctx,k,v)
	if not v then
		id10t 'no such command'
	end

	if v.help then
		local fe = ctx.sty[io.stderr]
		local defs, synt = ''
		if type(v.syntax) == 'table' then
			synt = v.syntax[1]
			local pad = string.rep(' ', #k+5)
			for i=2,#v.syntax do
				defs = defs .. pad .. fe.color(v.syntax[i],5) .. '\n'
			end
		else synt = v.syntax end

		io.stderr:write(string.format(
			"  > %s %s\n" .. defs ..
			"    %s\n",
			fe.br(k), synt and fe.br(fe.color(synt,5)) or '',
			fe.em(fe.color(v.help,4,true))))
	end
end

function cmds.help.exec(ctx,cmd)
	if cmd then
		showHelp(ctx, cmd, cmds[cmd])
	else
		for cmd,c in pairs(cmds) do
			showHelp(ctx, cmd, c)
		end
	end
end

local globalFlags <const> = {
	human = {'h','human','enable human-readable exports'};
	ident = {'i','ident','show identifier paths for all items'}
}

local function
usage(me,ctx)
	local ln = 0
	local ct = {}
	local fe = ctx.sty[io.stderr]
	local fstr = ""
	local flagHelp = {}
	for k,v in pairs(globalFlags) do
		fstr = fstr .. v[1]
		table.insert(flagHelp, string.format("  -%s --%s: %s\n",table.unpack(v)))
	end
	io.stderr:write(string.format(fe.br"usage:".." %s [-%s] <file> [<command> [args…]]\n",me,fstr) .. table.concat(flagHelp))
	--[[
	for k,v in pairs(cmds) do
		local n = 1 + utf8.len(k) + utf8.len(v.syntax)
		ct[k] = n
		if n > ln then ln = n end
	end
	for k,v in pairs(cmds) do
		local pad = string.rep(" ", ln - ct[k] + 3)
		io.stderr:write(string.format("   "..fe.br'%s %s'.."%s%s\n",
			k, v.syntax, pad, v.help))
	end]]
	for k,v in pairs(cmds) do
		showHelp(ctx,k,v)
	end
	return 64
end

local function
dispatch(argv, ctx)
	local ferr = ctx.sty[io.stderr]
	local args = {}
	local flags = {}
	local i = 1 while i <= #argv do
		local a = argv[i]
		if a == '--' then i=i+1 break
		elseif a:sub(1,2) == '--' then
			local fs <const> = a:sub(3)
			for k,v in pairs(globalFlags) do
				if v[2] == fs then flags[k] = true end
			end
		elseif a:sub(1,1) == '-' then
			for p,cp in utf8.codes(''), a, #'-' do
				local c <const> = utf8.char(cp)
				for k,v in pairs(globalFlags) do
					if v[1] == c then flags[k] = true break end
				end
			end
		else table.insert(args, a) end
	i = i + 1 end
	for j=i,#argv do table.insert(args,argv[j]) end

	local file, cmd = table.unpack(args)
	if cmd and cmds[cmd] then
		local c,fd,dict = cmds[cmd]
		if (not c.raw) and not c.nofile then
			fd = safeopen(file, "rb")
			dict = readDict(fd:read 'a')
			fd:close()
			-- lua io has no truncate method, so we must
			-- rely on the clobbering behavior of the open()
			-- call instead :(
		end

		cmds[cmd].exec({
			sty = ctx.sty;
			try = ctx.try;
			log = ctx.log;

			flags = flags;
			file = file;
			fd = fd;
			dict = dict;
		}, table.unpack(args,3))

		if (not c.raw) and c.write then
			local output = writeDict(dict)
			-- writeDict should always be given a chance to
			-- bail before the previous file is destroyed!!
			-- you don't want one bug to wipe out your entire
			-- dictionary in one fell swoop
			fd = safeopen(file,'w+b')
			fd:write(output)
			fd:close()
		end

		return 0
	else
		return usage(argv[0], ctx)
	end
end


local argv if arg
	then argv = arg
	else argv = {[0] = 'parvan', ...}
end

local sty = {
	[io.stdout] = ansi.formatter(io.stdout);
	[io.stderr] = ansi.formatter(io.stderr);
};

local function log(lvl, msg)
	local colors = {fatal=1,warn=3,info=4,debug=2}
	local ferr = sty[io.stderr]
	io.stderr:write(string.format(
		ferr.color(ferr.br("(%s)"),colors[lvl]).." %s\n", lvl, msg))
end

local function stacktrace(err)
	return debug.traceback(err,3)
end

local function try(fn,...)
	-- a wrapper around pcall that produces a standard error
	-- message format when an error occurs
	local res = { xpcall(fn,stacktrace,...) }
	if not res[1] then
		log('fatal', res[2])
	end
	return table.unpack(res)
end

local ok, res = xpcall(dispatch, stacktrace, argv, {
	try = try, sty = sty, log = log
})

if not ok then
	log('fatal', res)
	os.exit(1)
end

os.exit(res)