-- tracker.lua — the object tracker.
--
-- Three-level navigation (docs/05-decisions.md D2):
--
--   Ctrl+PageUp / Ctrl+PageDown    category   "Creatures"
--   PageUp     / PageDown          kind       "rat"
--   Shift+PageUp / Shift+PageDown  instance   that specific rat
--   Home                           announce distance + direction
--   Ctrl+Home                      walk there (what a left click does)
--   Shift+End                      nearest known exit, without touching the above
--
-- Two hard rules:
--
--   * Never report anything outside FoV / rememberedFoV. The tracker must not
--     become a cheat -- it exposes what a sighted player could see, no more.
--   * Never scan per frame. A scan walks xMax x yMax; it runs on keypress and is
--     cached until the world changes under it.

local speech = require("accessibility.speech")
local describe = require("accessibility.describe")
local categories = require("accessibility.categories")

local tracker = {}

--------------------------------------------------------------------------------
-- State
--------------------------------------------------------------------------------

local categoryIndex = 1
local kindIndex = 1
local instanceIndex = 1

local scan -- { [categoryKey] = { kinds = { {key, name, instances={{x,y,ref},..}}, .. } } }
local scanSignature

-- What the player last deliberately selected, so a rescan can put the cursor back
-- on it. Indices alone are useless here: the lists are distance-sorted, so a
-- single step re-orders them and a bare index silently selects a different rat.
local selectedKindKey    -- string, or nil
local selectedInstance   -- {ref = actor} for creatures, {x, y} for tiles

--------------------------------------------------------------------------------
-- Scanning
--------------------------------------------------------------------------------

local function getLevel()
	local ok, world = pcall(require, "models.world")
	if not ok or not world.currentLevel then
		return nil
	end
	return world.currentLevel
end

-- Cheap staleness key. Position matters because everything is sorted by distance
-- to the player; turn matters because creatures move and containers empty.
local function signatureFor(level)
	local actor = level.playerActor
	local turn = level.world and level.world.turn or 0
	return string.format("%s:%s:%s:%s",
		tostring(level.name), tostring(actor and actor.x), tostring(actor and actor.y), tostring(turn))
end

local function seenAt(level, x, y)
	if level.FoV and level.FoV[x] and level.FoV[x][y] then
		return true, true
	end
	if level.rememberedFoV and level.rememberedFoV[x] and level.rememberedFoV[x][y] then
		return true, false
	end
	return false, false
end

local function newBucket()
	return {kinds = {}, byKind = {}}
end

-- ref, when given, is the actor table itself: a creature's identity survives it
-- walking, its coordinates do not.
local function addTo(bucket, kindKey, kindName, x, y, ref)
	if not kindKey then
		return
	end

	local kind = bucket.byKind[kindKey]

	if not kind then
		kind = {key = kindKey, name = kindName, instances = {}}
		bucket.byKind[kindKey] = kind
		bucket.kinds[#bucket.kinds + 1] = kind
	end

	kind.instances[#kind.instances + 1] = {x = x, y = y, ref = ref}
end

function tracker.rescan(force)
	local level = getLevel()
	if not level or not level.playerActor then
		scan = nil
		return nil
	end

	local signature = signatureFor(level)
	if not force and scan and signature == scanSignature then
		return scan
	end

	local buckets = {}
	for _, category in ipairs(categories.list) do
		buckets[category.key] = newBucket()
	end

	local px, py = level.playerActor.x, level.playerActor.y

	-- Creatures come from the actor list, not the grid.
	for _, actor in ipairs(level.actors or {}) do
		if actor ~= level.playerActor
			and actor.x and actor.y
			and actor.visibilityAlpha ~= 0
		then
			local visible = level.FoV and level.FoV[actor.x] and level.FoV[actor.x][actor.y]
			if visible then
				addTo(buckets.creatures, categories.actorKind(actor),
					categories.actorName(actor), actor.x, actor.y, actor)
			end
		end
	end

	-- Tiles.
	for x = 1, level.xMax or 0 do
		if level.grid[x] then
			for y = 1, level.yMax or 0 do
				local stack = level.grid[x][y]
				if stack and seenAt(level, x, y) then
					local claimed = {}

					for i = #stack, 1, -1 do
						local tile = stack[i]
						local key = categories.classifyTile(tile)

						-- One entry per category per cell: a cell can hold both a
						-- door and a floor, but not two doors worth reporting.
						if key and not claimed[key] then
							claimed[key] = true
							addTo(buckets[key], categories.tileKind(tile),
								categories.tileName(tile), x, y)
						end
					end

					if not claimed.terrain then
						local ok, isWater = pcall(level.isWaterTile, x, y)
						if ok and isWater then
							addTo(buckets.terrain, "water", "water", x, y)
						end
					end
				end
			end
		end
	end

	-- Sort instances by distance to the player, and kinds by their nearest
	-- instance, so both levels of navigation move outward.
	local function chebyshev(a)
		return math.max(math.abs(a.x - px), math.abs(a.y - py))
	end

	for _, bucket in pairs(buckets) do
		for _, kind in ipairs(bucket.kinds) do
			table.sort(kind.instances, function(a, b)
				return chebyshev(a) < chebyshev(b)
			end)
		end
		table.sort(bucket.kinds, function(a, b)
			return chebyshev(a.instances[1]) < chebyshev(b.instances[1])
		end)
	end

	scan = buckets
	scanSignature = signature
	tracker.reanchor()
	return scan
end

--------------------------------------------------------------------------------
-- Selection stability
--
-- The scan is rebuilt from scratch every turn and both lists are distance-sorted,
-- so the same rat is at a different index each time it or the player moves. We
-- therefore track the selection by identity and re-derive the indices after every
-- rescan. The selection is only dropped when the thing genuinely stops being
-- reported -- out of FoV, killed, picked up.
--------------------------------------------------------------------------------

local function sameInstance(instance, wanted)
	if not instance or not wanted then
		return false
	end
	if wanted.ref then
		return instance.ref == wanted.ref
	end
	return instance.ref == nil and instance.x == wanted.x and instance.y == wanted.y
end

-- Record what is selected right now. Called after every deliberate move of the
-- selection, never during a rescan.
local function remember()
	local category = categories.list[categoryIndex]
	local bucket = scan and category and scan[category.key]
	local kind = bucket and bucket.kinds[kindIndex]

	selectedKindKey = kind and kind.key or nil

	local instance = kind and kind.instances[instanceIndex]
	if instance then
		selectedInstance = instance.ref and {ref = instance.ref} or {x = instance.x, y = instance.y}
	else
		selectedInstance = nil
	end
end

function tracker.reanchor()
	local category = categories.list[categoryIndex]
	local bucket = scan and category and scan[category.key]

	if not bucket or not selectedKindKey then
		return
	end

	local foundKind
	for i, kind in ipairs(bucket.kinds) do
		if kind.key == selectedKindKey then
			kindIndex, foundKind = i, kind
			break
		end
	end

	if not foundKind then
		-- The kind is gone from view entirely. Let the clamp in currentKind pick
		-- whatever is nearest and stop pretending we still have a selection.
		selectedKindKey, selectedInstance = nil, nil
		return
	end

	if not selectedInstance then
		return
	end

	for i, instance in ipairs(foundKind.instances) do
		if sameInstance(instance, selectedInstance) then
			instanceIndex = i
			return
		end
	end

	-- Kind still visible, this particular one is not.
	selectedInstance = nil
end

--------------------------------------------------------------------------------
-- Access
--------------------------------------------------------------------------------

local function currentCategory()
	return categories.list[categoryIndex]
end

local function currentBucket()
	local data = tracker.rescan()
	local category = currentCategory()
	if not data or not category then
		return nil
	end
	return data[category.key]
end

local function currentKind()
	local bucket = currentBucket()
	if not bucket or #bucket.kinds == 0 then
		return nil
	end
	kindIndex = math.max(1, math.min(kindIndex, #bucket.kinds))
	return bucket.kinds[kindIndex], bucket
end

local function currentInstance()
	local kind = currentKind()
	if not kind then
		return nil
	end
	instanceIndex = math.max(1, math.min(instanceIndex, #kind.instances))
	return kind.instances[instanceIndex], kind
end

-- What is selected right now, after any pending rescan. Used by the testbed, and
-- handy for anything that wants to follow the tracker cursor.
function tracker.currentSelection()
	local instance, kind = currentInstance()
	if not instance then
		return nil
	end
	return {
		category = currentCategory() and currentCategory().key,
		kind = kind.key,
		name = kind.name,
		x = instance.x,
		y = instance.y,
		ref = instance.ref,
	}
end

--------------------------------------------------------------------------------
-- Announcements
--------------------------------------------------------------------------------

local function offsetFromPlayer(instance)
	local level = getLevel()
	local actor = level and level.playerActor
	if not actor then
		return ""
	end
	return describe.offset(instance.x - actor.x, instance.y - actor.y)
end

local function announceCategory()
	local category = currentCategory()
	local bucket = currentBucket()

	if not category then
		return
	end

	if not bucket or #bucket.kinds == 0 then
		speech.say(category.name .. ", none", true)
		return
	end

	local count = #bucket.kinds
	speech.say(string.format("%s, %d %s", category.name, count,
		count == 1 and "kind" or "kinds"), true)
end

local function announceKind()
	local kind, bucket = currentKind()

	if not kind then
		local category = currentCategory()
		speech.say((category and category.name or "Nothing") .. ", none", true)
		return
	end

	local total = #kind.instances
	local instance = kind.instances[1]

	speech.say(string.format("%s, %d, nearest %s, %d of %d",
		kind.name, total, offsetFromPlayer(instance), kindIndex, #bucket.kinds), true)
end

local function announceInstance()
	local instance, kind = currentInstance()

	if not instance then
		return
	end

	speech.say(string.format("%s %d of %d, %s",
		kind.name, instanceIndex, #kind.instances, offsetFromPlayer(instance)), true)
end

--------------------------------------------------------------------------------
-- Navigation
--------------------------------------------------------------------------------

local function cycle(value, delta, count)
	if count == 0 then
		return 1
	end
	value = value + delta
	if value < 1 then
		value = count
	elseif value > count then
		value = 1
	end
	return value
end

function tracker.cycleCategory(delta)
	tracker.rescan()
	categoryIndex = cycle(categoryIndex, delta, #categories.list)
	kindIndex = 1
	instanceIndex = 1
	remember()
	announceCategory()
end

function tracker.cycleKind(delta)
	local bucket = currentBucket()
	if not bucket or #bucket.kinds == 0 then
		announceKind()
		return
	end
	kindIndex = cycle(kindIndex, delta, #bucket.kinds)
	instanceIndex = 1
	remember()
	announceKind()
end

function tracker.cycleInstance(delta)
	local kind = currentKind()
	if not kind then
		announceKind()
		return
	end
	instanceIndex = cycle(instanceIndex, delta, #kind.instances)
	remember()
	announceInstance()
end

-- Home: where is the current thing, and how far is it to actually walk there.
function tracker.announceLocation()
	local instance, kind = currentInstance()

	if not instance then
		local category = currentCategory()
		speech.say((category and category.name or "Tracker") .. ", nothing selected", true)
		return
	end

	local parts = {
		string.format("%s, %s", kind.name, offsetFromPlayer(instance)),
	}

	-- Straight-line offset can be badly misleading indoors -- a chest three tiles
	-- north through a wall may be twenty steps away. Path length is the number
	-- that actually matters.
	local level = getLevel()
	if level then
		local ok, path = pcall(level.calculatePathFromPlayer, instance.x, instance.y)
		if ok and path and #path > 0 then
			parts[#parts + 1] = #path .. (#path == 1 and " step by path" or " steps by path")
		elseif ok then
			parts[#parts + 1] = "no path"
		end
	end

	speech.say(table.concat(parts, ", "), true)
end

--------------------------------------------------------------------------------
-- Nearest exit
--------------------------------------------------------------------------------
--
-- Exits are already a tracker category, but reaching them costs several keypresses
-- of category cycling and clobbers whatever you were tracking. "Where is the way
-- out" is asked often enough, and under enough pressure, to deserve one key that
-- answers without disturbing the selection.
--
-- This does NOT use the tracker's own scan. The game has the exact primitive
-- already: level.getListByTag("exit") (modules/level.lua:1382) walks the grid,
-- gates on FoV or rememberedFoV, skips hidden tiles and returns the results
-- sorted by distance to the player. Reusing it means the FoV rule is enforced by
-- vanilla rather than restated here.
--
-- Note for anyone tempted by level.exits: it does not exist at runtime. It is
-- packed as nil (modules/level.lua:416) and never assigned; `exits` is a
-- generator parameter that gets baked into individual tiles.

local exitTemplates

local function getExitTemplates()
	if exitTemplates then
		return exitTemplates
	end

	local ok, templatesByTag = pcall(require, "modules.tile.templatesByTag")
	exitTemplates = (ok and templatesByTag and templatesByTag.exit) or {}
	return exitTemplates
end

-- getListByTag returns bare {x, y}, so the name has to come back off the stack.
local function exitNameAt(level, x, y)
	local stack = level.grid and level.grid[x] and level.grid[x][y]
	if type(stack) ~= "table" then
		return "exit"
	end

	local templates = getExitTemplates()

	for i = #stack, 1, -1 do
		local tile = stack[i]
		if tile and not tile.isHidden and templates[tile.templateId] then
			return categories.tileName(tile)
		end
	end

	return "exit"
end

-- Shift+End: the nearest way off this level.
function tracker.announceNearestExit()
	local level = getLevel()
	local actor = level and level.playerActor

	if not level or not actor then
		speech.say("No exits known", true)
		return
	end

	local ok, list = pcall(level.getListByTag, "exit")
	if not ok or type(list) ~= "table" or not list[1] then
		speech.say("No exits known", true)
		return
	end

	local nearest = list[1]

	local parts = {
		string.format("%s, %s", exitNameAt(level, nearest.x, nearest.y),
			describe.offset(nearest.x - actor.x, nearest.y - actor.y)),
	}

	-- Same reasoning as announceLocation: straight-line offset is misleading
	-- indoors, and the path count truncates to one step while threatened.
	local okPath, path = pcall(level.calculatePathFromPlayer, nearest.x, nearest.y)
	if okPath and path and #path > 0 then
		parts[#parts + 1] = #path .. (#path == 1 and " step by path" or " steps by path")
	elseif okPath then
		parts[#parts + 1] = "no path"
	end

	if #list > 1 then
		parts[#parts + 1] = #list .. " known"
	end

	speech.say(table.concat(parts, ", "), true)
end

-- Ctrl+Home: actually go there.
--
-- This is the keyboard equivalent of a left click on the tile (states/ingame.lua
-- mousepressed): build a path with calculatePathFromPlayer, then hand it to the
-- level's input buffer with the ingame state as the owner. We deliberately use
-- the game's own two-branch shape -- a one-step path goes through playerInput
-- directly, because bufferInput for a single move re-enters the buffer machinery
-- for no reason.
--
-- Most things worth tracking stand on impassable tiles (a rat, a chest), and
-- calculatePathFromPlayer refuses those outright. So when the tile itself has no
-- path we path to the best neighbouring tile instead, which is what a player
-- clicking a monster expects to happen anyway.
local function pathTo(level, x, y)
	local ok, path = pcall(level.calculatePathFromPlayer, x, y)
	if ok and path and #path > 0 then
		return path, true
	end

	local best
	for dx = -1, 1 do
		for dy = -1, 1 do
			if dx ~= 0 or dy ~= 0 then
				local okNear, near = pcall(level.calculatePathFromPlayer, x + dx, y + dy)
				if okNear and near and #near > 0 and (not best or #near < #best) then
					best = near
				end
			end
		end
	end

	return best, false
end

function tracker.walkToSelection()
	local instance, kind = currentInstance()

	if not instance then
		local category = currentCategory()
		speech.say((category and category.name or "Tracker") .. ", nothing selected", true)
		return
	end

	-- Walking is only meaningful on the map. In a menu or the observe cursor the
	-- input buffer belongs to another state and feeding it moves would be a bug.
	local okStates, states = pcall(require, "states")
	if not okStates or states.getCurrent() ~= "ingame" then
		speech.say("Cannot walk from here", true)
		return
	end

	local level = getLevel()
	local actor = level and level.playerActor
	if not actor then
		return
	end

	if instance.x == actor.x and instance.y == actor.y then
		speech.say(kind.name .. ", already here", true)
		return
	end

	local path, exact = pathTo(level, instance.x, instance.y)
	if not path then
		speech.say(kind.name .. ", no path", true)
		return
	end

	-- Same module key states.lua uses, so we share its cached instance.
	local okIngame, ingame = pcall(require, "states/ingame")
	if not okIngame then
		return
	end

	pcall(level.skipAllAnimations)

	local okMove, err
	if #path == 1 then
		okMove, err = pcall(level.playerInput, "move",
			actor.x + path[1].dx, actor.y + path[1].dy, ingame)
	else
		okMove, err = pcall(level.bufferInput, "move", path, ingame)
	end

	if not okMove then
		print("[accessibility] walk to selection failed: " .. tostring(err))
		speech.say(kind.name .. ", cannot walk there", true)
		return
	end

	-- calculatePathFromPlayer truncates to a single step while the player is
	-- threatened, so the spoken count is the number of steps that will actually
	-- be taken, not the distance to the target.
	speech.say(string.format("Walking %s %s, %d %s",
		exact and "to" or "next to", kind.name,
		#path, #path == 1 and "step" or "steps"), true)
end

--------------------------------------------------------------------------------
-- Key registration
--------------------------------------------------------------------------------

function tracker.registerKeys(hotkeys)
	hotkeys.bind("pageup", "ctrl", function() tracker.cycleCategory(-1) end)
	hotkeys.bind("pagedown", "ctrl", function() tracker.cycleCategory(1) end)

	hotkeys.bind("pageup", "shift", function() tracker.cycleInstance(-1) end)
	hotkeys.bind("pagedown", "shift", function() tracker.cycleInstance(1) end)

	hotkeys.bind("pageup", nil, function() tracker.cycleKind(-1) end)
	hotkeys.bind("pagedown", nil, function() tracker.cycleKind(1) end)

	hotkeys.bind("home", nil, tracker.announceLocation)
	hotkeys.bind("home", "ctrl", tracker.walkToSelection)

	hotkeys.bind("end", "shift", tracker.announceNearestExit)
end

return tracker