--- AceTab-3.0 provides support for tab-completion.
-- Note: This library is not yet finalized.
-- @class file
-- @name AceTab-3.0
-- @release $Id: AceTab-3.0.lua 1202 2019-05-15 23:11:22Z nevcairiel $

local ACETAB_MAJOR, ACETAB_MINOR = 'AceTab-3.0', 9
local AceTab, oldminor = LibStub:NewLibrary(ACETAB_MAJOR, ACETAB_MINOR)

if not AceTab then return end -- No upgrade needed

AceTab.registry = AceTab.registry or {}

-- local upvalues
local _G = _G
local pairs = pairs
local ipairs = ipairs
local type = type
local registry = AceTab.registry

local strfind = string.find
local strsub = string.sub
local strlower = string.lower
local strformat = string.format
local strmatch = string.match

local function printf(...)
	DEFAULT_CHAT_FRAME:AddMessage(strformat(...))
end

local function getTextBeforeCursor(this, start)
	return strsub(this:GetText(), start or 1, this:GetCursorPosition())
end

-- Hook OnTabPressed and OnTextChanged for the frame, give it an empty matches table, and set its curMatch to 0, if we haven't done so already.
local function hookFrame(f)
	if f.hookedByAceTab3 then return end
	f.hookedByAceTab3 = true
	if f == ChatEdit_GetActiveWindow() then
		local origCTP = ChatEdit_CustomTabPressed
		function ChatEdit_CustomTabPressed(...)
			if AceTab:OnTabPressed(f) then
				return origCTP(...)
			else
				return true
			end
		end
	else
		local origOTP = f:GetScript('OnTabPressed')
		if type(origOTP) ~= 'function' then
			origOTP = function() end
		end
		f:SetScript('OnTabPressed', function(...)
			if AceTab:OnTabPressed(f) then
				return origOTP(...)
			end
		end)
	end
	f.at3curMatch = 0
	f.at3matches = {}
end

local firstPMLength

local fallbacks, notfallbacks = {}, {}  -- classifies completions into those which have preconditions and those which do not.  Those without preconditions are only considered if no other completions have matches.
local pmolengths = {}  -- holds the number of characters to overwrite according to pmoverwrite and the current prematch
-- ------------------------------------------------------------------------------
-- RegisterTabCompletion( descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite )
-- See http://www.wowace.com/wiki/AceTab-2.0 for detailed API documentation
--
-- descriptor	string					Unique identifier for this tab completion set
--
-- prematches	string|table|nil		String match(es) AFTER which this tab completion will apply.
--										AceTab will ignore tabs NOT preceded by the string(s).
--										If no value is passed, will check all tabs pressed in the specified editframe(s) UNLESS a more-specific tab complete applies.
--
-- wordlist		function|table			Function that will be passed a table into which it will insert strings corresponding to all possible completions, or an equivalent table.
--										The text in the editbox, the position of the start of the word to be completed, and the uncompleted partial word
--										are passed as second, third, and fourth arguments, to facilitate pre-filtering or conditional formatting, if desired.
--
-- usagefunc	function|boolean|nil	Usage statement function.  Defaults to the wordlist, one per line.  A boolean true squelches usage output.
--
-- listenframes	string|table|nil		EditFrames to monitor.  Defaults to ChatFrameEditBox.
--
-- postfunc		function|nil			Post-processing function.  If supplied, matches will be passed through this function after they've been identified as a match.
--
-- pmoverwrite	boolean|number|nil		Offset the beginning of the completion string in the editbox when making a completion.  Passing a boolean true indicates that we want to overwrite
--										the entire prematch string, and passing a number will overwrite that many characters prior to the cursor.
--										This is useful when you want to use the prematch as an indicator character, but ultimately do not want it as part of the text, itself.
--
-- no return
-- ------------------------------------------------------------------------------
function AceTab:RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite)
	-- Arg checks
	if type(descriptor) ~= 'string' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'descriptor' - string expected.", 3) end
	if prematches and type(prematches) ~= 'string' and type(prematches) ~= 'table' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'prematches' - string, table, or nil expected.", 3) end
	if type(wordlist) ~= 'function' and type(wordlist) ~= 'table' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'wordlist' - function or table expected.", 3) end
	if usagefunc and type(usagefunc) ~= 'function' and type(usagefunc) ~= 'boolean' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'usagefunc' - function or boolean expected.", 3) end
	if listenframes and type(listenframes) ~= 'string' and type(listenframes) ~= 'table' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'listenframes' - string or table expected.", 3) end
	if postfunc and type(postfunc) ~= 'function' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'postfunc' - function expected.", 3) end
	if pmoverwrite and type(pmoverwrite) ~= 'boolean' and type(pmoverwrite) ~= 'number' then error("Usage: RegisterTabCompletion(descriptor, prematches, wordlist, usagefunc, listenframes, postfunc, pmoverwrite): 'pmoverwrite' - boolean or number expected.", 3) end

	local pmtable

	if type(prematches) == 'table' then
		pmtable = prematches
		notfallbacks[descriptor] = true
	else
		pmtable = {}
		-- Mark this group as a fallback group if no value was passed.
		if not prematches then
			pmtable[1] = ""
			fallbacks[descriptor] = true
		-- Make prematches into a one-element table if it was passed as a string.
		elseif type(prematches) == 'string' then
			pmtable[1] = prematches
			if prematches == "" then
				fallbacks[descriptor] = true
			else
				notfallbacks[descriptor] = true
			end
		end
	end

	-- Make listenframes into a one-element table if it was not passed a table of frames.
	if not listenframes then  -- default
		listenframes = {}
		for i = 1, NUM_CHAT_WINDOWS do
			listenframes[i] = _G["ChatFrame"..i.."EditBox"]
		end
	elseif type(listenframes) ~= 'table' or type(listenframes[0]) == 'userdata' and type(listenframes.IsObjectType) == 'function' then  -- single frame or framename
		listenframes = { listenframes }
	end

	-- Hook each registered listenframe and give it a matches table.
	for _, f in pairs(listenframes) do
		if type(f) == 'string' then
			f = _G[f]
		end
		if type(f) ~= 'table' or type(f[0]) ~= 'userdata' or type(f.IsObjectType) ~= 'function' then
			error(format(ACETAB_MAJOR..": Cannot register frame %q; it does not exist", f:GetName()))
		end
		if f then
			if f:GetObjectType() ~= 'EditBox' then
				error(format(ACETAB_MAJOR..": Cannot register frame %q; it is not an EditBox", f:GetName()))
			else
				hookFrame(f)
			end
		end
	end

	-- Everything checks out; register this completion.
	if not registry[descriptor] then
		registry[descriptor] = { prematches = pmtable, wordlist = wordlist, usagefunc = usagefunc, listenframes = listenframes, postfunc = postfunc, pmoverwrite = pmoverwrite }
	end
end

function AceTab:IsTabCompletionRegistered(descriptor)
	return registry and registry[descriptor]
end

function AceTab:UnregisterTabCompletion(descriptor)
	registry[descriptor] = nil
	pmolengths[descriptor] = nil
	fallbacks[descriptor] = nil
	notfallbacks[descriptor] = nil
end

-- ------------------------------------------------------------------------------
-- gcbs( s1, s2 )
--
-- s1		string		First string to be compared
--
-- s2		string		Second string to be compared
--
-- returns the greatest common substring beginning s1 and s2
-- ------------------------------------------------------------------------------
local function gcbs(s1, s2)
	if not s1 and not s2 then return end
	if not s1 then s1 = s2 end
	if not s2 then s2 = s1 end
	if #s2 < #s1 then
		s1, s2 = s2, s1
	end
	if strfind(strlower(s2), "^"..strlower(s1)) then
		return s1
	else
		return gcbs(strsub(s1, 1, -2), s2)
	end
end

local cursor  -- Holds cursor position.  Set in :OnTabPressed().
-- ------------------------------------------------------------------------------
-- cycleTab()
-- For when a tab press has multiple possible completions, we need to allow the user to press tab repeatedly to cycle through them.
-- If we have multiple possible completions, all tab presses after the first will call this function to cycle through and insert the different possible matches.
-- This function will stop being called after OnTextChanged() is triggered by something other than AceTab (i.e. the user inputs a character).
-- ------------------------------------------------------------------------------
local previousLength, cMatch, matched, postmatch
local function cycleTab(this)
	cMatch = 0  -- Counter across all sets.  The pseudo-index relevant to this value and corresponding to the current match is held in this.at3curMatch
	matched = false

	-- Check each completion group registered to this frame.
	for desc, compgrp in pairs(this.at3matches) do

		-- Loop through the valid completions for this set.
		for m, pm in pairs(compgrp) do
			cMatch = cMatch + 1
			if cMatch == this.at3curMatch then  -- we're back to where we left off last time through the combined list
				this.at3lastMatch = m
				this.at3lastWord = pm
				this.at3curMatch = cMatch + 1 -- save the new cMatch index
				matched = true
				break
			end
		end
		if matched then break end
	end

	-- If our index is beyond the end of the list, reset the original uncompleted substring and let the cycle start over next time tab is pressed.
	if not matched then
		this.at3lastMatch = this.at3origMatch
		this.at3lastWord = this.at3origWord
		this.at3curMatch = 1
	end

	-- Insert the completion.
	this:HighlightText(this.at3matchStart-1, cursor)
	this:Insert(this.at3lastWord or '')
	this.at3_last_precursor = getTextBeforeCursor(this) or ''
end

local IsSecureCmd = IsSecureCmd

local cands, candUsage = {}, {}
local numMatches = 0
local firstMatch, hasNonFallback, allGCBS, setGCBS, usage
local text_precursor, text_all, text_pmendToCursor
local matches, usagefunc  -- convenience locals

-- Fill the this.at3matches[descriptor] tables with matching completion pairs for each entry, based on
-- the partial string preceding the cursor position and using the corresponding registered wordlist.
--
-- The entries of the matches tables are of the format raw_match = formatted_match, where raw_match is the plaintext completion and
-- formatted_match is the match after being formatted/altered/processed by the registered postfunc.
-- If no postfunc exists, then the formatted and raw matches are the same.
local pms, pme, pmt, prematchStart, prematchEnd, text_prematch, entry
local function fillMatches(this, desc, fallback)
	entry = registry[desc]
	-- See what frames are registered for this completion group.  If the frame in which we pressed tab is one of them, then we start building matches.
	for _, f in ipairs(entry.listenframes) do
		if f == this then

			-- Try each precondition string registered for this completion group.
			for _, prematch in ipairs(entry.prematches) do

				-- Test if our prematch string is satisfied.
				-- If it is, then we find its last occurence prior to the cursor, calculate and store its pmoverwrite value (if applicable), and start considering completions.
				if fallback then prematch = "%s" end

				-- Find the last occurence of the prematch before the cursor.
				pms, pme, pmt = nil, 1, ''
				text_prematch, prematchEnd, prematchStart = nil, nil, nil
				while true do
					pms, pme, pmt = strfind(text_precursor, "("..prematch..")", pme)
					if pms then
						prematchStart, prematchEnd, text_prematch = pms, pme, pmt
						pme = pme + 1
					else
						break
					end
				end

				if not prematchStart and fallback then
					prematchStart, prematchEnd, text_prematch = 0, 0, ''
				end
				if prematchStart then
					-- text_pmendToCursor should be the sub-word/phrase to be completed.
					text_pmendToCursor = strsub(text_precursor, prematchEnd + 1)

					-- How many characters should we eliminate before the completion before writing it in.
					pmolengths[desc] = entry.pmoverwrite == true and #text_prematch or entry.pmoverwrite or 0

					-- This is where we will insert completions, taking the prematch overwrite into account.
					this.at3matchStart = prematchEnd + 1 - (pmolengths[desc] or 0)

					-- We're either a non-fallback set or all completions thus far have been fallback sets, and the precondition matches.
					-- Create cands from the registered wordlist, filling it with all potential (unfiltered) completion strings.
					local wordlist = entry.wordlist
					local cands = type(wordlist) == 'table' and wordlist or {}
					if type(wordlist) == 'function' then
						wordlist(cands, text_all, prematchEnd + 1, text_pmendToCursor)
					end
					if cands ~= false then
						matches = this.at3matches[desc] or {}
						for i in pairs(matches) do matches[i] = nil end

						-- Check each of the entries in cands to see if it completes the word before the cursor.
						-- Finally, increment our match count and set firstMatch, if appropriate.
						for _, m in ipairs(cands) do
							if strfind(strlower(m), strlower(text_pmendToCursor), 1, 1) == 1 then  -- we have a matching completion!
								hasNonFallback = hasNonFallback or (not fallback)
								matches[m] = entry.postfunc and entry.postfunc(m, prematchEnd + 1, text_all) or m
								numMatches = numMatches + 1
								if numMatches == 1 then
									firstMatch = matches[m]
									firstPMLength = pmolengths[desc] or 0
								end
							end
						end
						this.at3matches[desc] = numMatches > 0 and matches or nil
					end
				end
			end
		end
	end
end

function AceTab:OnTabPressed(this)
	if this:GetText() == '' then return true end

	-- allow Blizzard to handle slash commands, themselves
	if this == ChatEdit_GetActiveWindow() then
		local command = this:GetText()
		if strfind(command, "^/[%a%d_]+$") then
			return true
		end
		local cmd = strmatch(command, "^/[%a%d_]+")
		if cmd and IsSecureCmd(cmd) then
			return true
		end
	end

	cursor = this:GetCursorPosition()

	text_all = this:GetText()
	text_precursor = getTextBeforeCursor(this) or ''

	-- If we've already found some matches and haven't done anything since the last tab press, then (continue) cycling matches.
	-- Otherwise, reset this frame's matches and proceed to creating our list of possible completions.
	this.at3lastMatch = this.at3curMatch > 0 and (this.at3lastMatch or this.at3origWord)
	-- Detects if we've made any edits since the last tab press.  If not, continue cycling completions.
	if text_precursor == this.at3_last_precursor then
		return cycleTab(this)
	else
		for i in pairs(this.at3matches) do this.at3matches[i] = nil end
		this.at3curMatch = 0
		this.at3origWord = nil
		this.at3origMatch = nil
		this.at3lastWord = nil
		this.at3lastMatch = nil
		this.at3_last_precursor = text_precursor
	end

	numMatches = 0
	firstMatch = nil
	firstPMLength = 0
	hasNonFallback = false
	for i in pairs(pmolengths) do pmolengths[i] = nil end

	for desc in pairs(notfallbacks) do
		fillMatches(this, desc)
	end
	if not hasNonFallback then
		for desc in pairs(fallbacks) do
			fillMatches(this, desc, true)
		end
	end

	if not firstMatch then
		this.at3_last_precursor = "\0"
		return true
	end

	-- We want to replace the entire word with our completion, so highlight it up to the cursor.
	-- If only one match exists, then stick it in there and append a space.
	if numMatches == 1 then
		-- HighlightText takes the value AFTER which the highlighting starts, so we have to subtract 1 to have it start before the first character.
		this:HighlightText(this.at3matchStart-1, cursor)

		this:Insert(firstMatch)
		this:Insert(" ")
	else
		-- Otherwise, we want to begin cycling through the valid completions.
		-- Beginning a cycle also causes the usage statement to be printed, if one exists.

		-- Print usage statements for each possible completion (and gather up the GCBS of all matches while we're walking the tables).
		allGCBS = nil
		for desc, matches in pairs(this.at3matches) do
			-- Don't print usage statements for fallback completion groups if we have 'real' completion groups with matches.
			if hasNonFallback and fallbacks[desc] then break end

			-- Use the group's description as a heading for its usage statements.
			DEFAULT_CHAT_FRAME:AddMessage(desc..":")

			usagefunc = registry[desc].usagefunc
			if not usagefunc then
				-- No special usage processing; just print a list of the (formatted) matches.
				for m, fm in pairs(matches) do
					DEFAULT_CHAT_FRAME:AddMessage(fm)
					allGCBS = gcbs(allGCBS, m)
				end
			else
				-- Print a usage statement based on the corresponding registered usagefunc.
				-- candUsage is the table passed to usagefunc to be filled with candidate = usage_statement pairs.
				if type(usagefunc) == 'function' then
					for i in pairs(candUsage) do candUsage[i] = nil end

					-- usagefunc takes the greatest common substring of valid matches as one of its args, so let's find that now.
					-- TODO: Make the GCBS function accept a vararg or table, after which we can just pass in the list of matches.
					setGCBS = nil
					for m in pairs(matches) do
						setGCBS = gcbs(setGCBS, m)
					end
					allGCBS = gcbs(allGCBS, setGCBS)
					usage = usagefunc(candUsage, matches, setGCBS, strsub(text_precursor, 1, prematchEnd))

					-- If the usagefunc returns a string, then the entire usage statement has been taken care of by usagefunc, and we need only to print it...
					if type(usage) == 'string' then
						DEFAULT_CHAT_FRAME:AddMessage(usage)

					-- ...otherwise, it should have filled candUsage with candidate-usage statement pairs, and we need to print the matching ones.
					elseif next(candUsage) and numMatches > 0 then
						for m, fm in pairs(matches) do
							if candUsage[m] then DEFAULT_CHAT_FRAME:AddMessage(strformat("%s - %s", fm, candUsage[m])) end
						end
					end
				end
			end

			if next(matches) then
				-- Replace the original string with the greatest common substring of all valid completions.
				this.at3curMatch = 1
				this.at3origWord = strsub(text_precursor, this.at3matchStart, this.at3matchStart + pmolengths[desc] - 1) .. allGCBS or ""
				this.at3origMatch = allGCBS or ""
				this.at3lastWord = this.at3origWord
				this.at3lastMatch = this.at3origMatch

				this:HighlightText(this.at3matchStart-1, cursor)
				this:Insert(this.at3origWord)
				this.at3_last_precursor = getTextBeforeCursor(this) or ''
			end
		end
	end
end