-- speech.lua — the mod's only route to text-to-speech.
--
-- Invariant: speech must NEVER throw. If the TTS backend is missing or broken,
-- every function here becomes a no-op and the game runs exactly as vanilla.
--
-- Utterances are queued within a frame rather than spoken immediately. A single
-- game turn routinely emits several console.print calls ("You hit the rat.",
-- "The rat dies.", "You feel cold."), and speaking each one with interrupt would
-- leave you hearing only the last. flush() joins the frame's queue into one
-- utterance, in order.

local speech = {}

local tts
local available = false
local failureReason

local queue = {}
local pendingInterrupt = false

-- Mirror every utterance to stdout. Worth keeping on by default during
-- development: it makes speech verifiable from the lovec console log rather than
-- only by ear, which matters when diagnosing whether a hook fired at all versus
-- fired with empty text.
speech.logToConsole = true

--------------------------------------------------------------------------------
-- Initialisation
--------------------------------------------------------------------------------

function speech.initialize()
	-- tolk.lua calls Tolk_Load() at require time and raises if the DLL is absent,
	-- so this pcall is load-bearing, not defensive garnish.
	local ok, result = pcall(require, "accessibility.vendor.love2talk.Love2talk")

	if not ok then
		available = false
		failureReason = tostring(result)
		print("[accessibility] TTS unavailable, running silent: " .. failureReason)
		return false
	end

	tts = result
	available = true
	print("[accessibility] TTS initialised")
	return true
end

function speech.isAvailable()
	return available
end

function speech.getFailureReason()
	return failureReason
end

-- Whether Tolk found a real speech channel (running screen reader, or SAPI
-- fallback). isAvailable() only means the library loaded.
function speech.hasSpeech()
	if not available or not tts.hasSpeech then
		return false
	end

	local ok, result = pcall(tts.hasSpeech)
	return ok and result or false
end

--------------------------------------------------------------------------------
-- Text normalisation
--------------------------------------------------------------------------------

-- Screen readers handle a single clean line far better than raw game strings,
-- which arrive with newlines (the game wraps its own text) and padding.
local function normalise(text)
	if text == nil then
		return nil
	end

	if type(text) ~= "string" then
		text = tostring(text)
	end

	text = text:gsub("[\r\n]+", ". ")
	text = text:gsub("%s+", " ")
	text = text:gsub("^%s+", ""):gsub("%s+$", "")

	if text == "" then
		return nil
	end

	return text
end

speech.normalise = normalise

--------------------------------------------------------------------------------
-- Speaking
--------------------------------------------------------------------------------

-- Queue text to be spoken at the end of this frame.
-- interrupt=true discards anything already queued this frame AND cuts off whatever
-- the screen reader is currently saying. Use it for keypress-driven output, where
-- the user expects an immediate answer to the key they just pressed.
function speech.say(text, interrupt)
	text = normalise(text)
	if not text then
		return
	end

	if interrupt then
		queue = {text}
		pendingInterrupt = true
	else
		queue[#queue + 1] = text
	end
end

-- Convenience: the common case for hotkeys.
function speech.interrupt(text)
	speech.say(text, true)
end

-- Speak immediately, bypassing the queue. Reserve this for urgent alerts (taking
-- damage) where waiting for end-of-frame is wrong.
function speech.immediate(text, interrupt)
	text = normalise(text)
	if not text or not available then
		return
	end

	pcall(tts.say, text, interrupt ~= false)
end

-- Called once per frame from init.lua's update hook.
function speech.flush()
	if #queue == 0 then
		return
	end

	local text = table.concat(queue, ". ")
	local shouldInterrupt = pendingInterrupt

	queue = {}
	pendingInterrupt = false

	if speech.logToConsole then
		print("[speech]" .. (shouldInterrupt and "!" or " ") .. " " .. text)
	end

	if not available then
		return
	end

	pcall(tts.say, text, shouldInterrupt)
end

function speech.silence()
	queue = {}
	pendingInterrupt = false

	if not available or not tts.silence then
		return
	end

	pcall(tts.silence)
end

-- Unreliable under screen readers (they don't report speaking state); only
-- meaningful with the SAPI fallback. Do not use for timing.
function speech.isSpeaking()
	if not available then
		return false
	end

	local ok, result = pcall(tts.isSpeaking)
	return ok and result or false
end

return speech