local tiny = require("lib.tiny")
require("lib.inspect")

---@class TinyDebug
local tinyDebug = {}

-- TODO: Track some debugName field when debugging?

local function worldMetaIndex()
    local worldMetaTable = getmetatable(tiny.world())
    return worldMetaTable.__index
end

local function getCurrentTimeMilliseconds()
    return love.timer.getTime() * 1000
end

--- Only applies to already-created systems!
--- Performs a `world:refresh()` to ensure that all added systems are installed.
---@param world World
function tinyDebug.logSystemUpdateTime(world)
    world:refresh()
    local systems = world.systems
    for i = 1, #systems do
        local system = systems[i]
        local wrappedUpdate = system.update
        system.update = function(...)
            local currentMs = getCurrentTimeMilliseconds()
            local ret = wrappedUpdate(...)
            local endTimeMs = getCurrentTimeMilliseconds()
            print(tostring(endTimeMs - currentMs) .. "ms taken to update system '" .. (system.name or i) .. "'")
            return ret
        end
    end
end

function tinyDebug.trackEntityAges()
    ENTITY_INIT_MS = { "ENTITY_INIT_MS" }
    -- tiny._trackEntityAges = true

    tiny._wrapAddEntity(function(_, entity)
        entity[ENTITY_INIT_MS] = getCurrentTimeMilliseconds()
    end)
end

--- Throws an error if trackEntityAges() has not been called
function tinyDebug.getEntityAgeMs(entity)
    if ENTITY_INIT_MS == nil then
        error("trackEntityAges() has not been enabled!")
    end
    return getCurrentTimeMilliseconds() - entity[ENTITY_INIT_MS]
end

function tinyDebug.warnWhenNonDataOnEntities()
    local function checkForNonData(e, nested, tableCache)
        nested = nested or false
        tableCache = tableCache or {}

        local valType = type(e)
        if valType == "table" then
            if tableCache[e] then
                return
            end
            tableCache[e] = true
            for k, v in pairs(e) do
                local keyWarning = checkForNonData(k, true, tableCache)
                if keyWarning then
                    return keyWarning
                end
                local valueWarning = checkForNonData(v, true, tableCache)
                if valueWarning then
                    return valueWarning
                end
            end
        elseif valType == "function" or valType == "thread" or valType == "userdata" then
            return valType
        end
    end

    tiny._wrapAddEntity(function(_, entity)
        local nonDataType = checkForNonData(entity)
        if nonDataType then
            print("Detected non-data type '" .. nonDataType .. "' on entity")
        end
    end)
end

function tinyDebug.throwOnUnusedEntities()
    ---@return boolean
    local function entityMatchesSomeSystem(world, entity)
        local systems = world.systems
        for i = 1, #systems do
            local system = systems[i]
            local filter = system.filter
            if filter and filter(system, entity) then
                return true
            end
        end

        return false
    end

    ---@return Entity[]
    local function anyUnmatchedEntities(world)
        local unmatchedEntities = {}
        local el = world.entities

        for i = 1, #el do
            if not entityMatchesSomeSystem(world, el[i]) then
                unmatchedEntities[#unmatchedEntities + 1] = el[i]
            end
        end

        return unmatchedEntities
    end

    local tinyUpdate = tiny.update
    worldMetaIndex().update = function(world, dt, filter)
        local ret = tinyUpdate(world, dt, filter)
        local ecAll = world:getEntityCount()
        local unmatchedEntities = anyUnmatchedEntities(world)
        if #unmatchedEntities ~= 0  then
            error("UNUSED ENTITY COUNT: " .. #unmatchedEntities .. "/" .. ecAll .. " " .. Inspect(unmatchedEntities, { depth = 2 }))
        end
        return ret
    end
end

return tinyDebug