-- mod.world: the supported way for mod code to act on the running
-- overworld.  Every method resolves the live OverworldState by scanning
-- the state stack for the isOverworld marker and returns nil, "no
-- overworld" when none is up -- called from the title screen this is a
-- quiet no-op, never a crash.  Reaching into OverworldState internals
-- stays unsupported; anything a mod legitimately needs belongs here.

local Logger = require("src.core.Logger")
local MapLoader = require("src.world.MapLoader")
local Runtime = require("src.mods.Runtime")

local WorldAPI = {}
WorldAPI.__index = WorldAPI

local NO_OVERWORLD = "no overworld"

function WorldAPI.new(game, modId)
  return setmetatable({ game = game, modId = modId }, WorldAPI)
end

-- the live overworld, or nil.  Game.overworld is the fast path; the stack
-- scan is the authority, so a state pushed over the world (a battle, a
-- menu) still resolves to the world underneath it.
function WorldAPI:overworld()
  local game = self.game
  local stack = game and game.stack
  local states = stack and stack.states
  if states then
    for i = #states, 1, -1 do
      if states[i].isOverworld then return states[i] end
    end
  end
  local ow = game and game.overworld
  if ow and ow.isOverworld and ow.map then return ow end
  return nil
end

function WorldAPI:current()
  local ow = self:overworld()
  if not ow or not ow.map then return nil, NO_OVERWORLD end
  local p = ow.player
  return { mapId = ow.map.id, x = p and p.cellX, y = p and p.cellY,
           facing = p and p.facing }
end

-- opts.arrive = "fly" | "teleport" picks the arrival FX; anything else
-- lands the player without one, like a scripted warp.
function WorldAPI:warpTo(mapId, x, y, facing, opts)
  local ow = self:overworld()
  if not ow then return nil, NO_OVERWORLD end
  if not self.game.data.maps[mapId] then
    return nil, "unknown map: " .. tostring(mapId)
  end
  if opts and (opts.arrive == "fly" or opts.arrive == "teleport") then
    ow.arriveWarp = opts.arrive
  end
  ow:startWarpTo(mapId, x, y, facing or "down", opts and opts.onDone,
                 { via = "warp", keepMusic = opts and opts.keepMusic })
  return true
end

-- save.objectToggles is the same store the spawn filter reads, so a toggle
-- on an inactive map takes effect the next time it is entered.
function WorldAPI:toggleObject(mapId, objName, visible)
  local save = self.game and self.game.save
  if not save then return nil, "no save" end
  save.objectToggles = save.objectToggles or {}
  save.objectToggles[mapId] = save.objectToggles[mapId] or {}
  save.objectToggles[mapId][objName] = visible and true or false
  Runtime.emit("world.object_toggled",
    { mapId = mapId, objName = objName, visible = visible and true or false })
  local ow = self:overworld()
  if ow and ow.map and ow.map.id == mapId then
    ow:setMap(mapId, ow.player.cellX, ow.player.cellY, ow.player.facing,
              { seamless = true, via = "reload", keepMusic = true })
  end
  return true
end

function WorldAPI:setFlag(name, value)
  local save = self.game and self.game.save
  if not save or not save.flags then return nil, "no save" end
  save.flags[name] = value
  return true
end

function WorldAPI:getFlag(name)
  local save = self.game and self.game.save
  return save and save.flags and save.flags[name]
end

-- active map only: this mutates the runtime Map and rebuilds the renderer.
-- A layout change that must survive a reload belongs in a maps patch.
function WorldAPI:replaceBlock(bx, by, block)
  local ow = self:overworld()
  if not ow or not ow.map then return nil, NO_OVERWORLD end
  ow:replaceBlock(bx, by, block)
  return true
end

-- objDef uses the same shape as maps[].objects.  Runtime objects are not
-- serialized: a permanent NPC belongs in a maps patch, this is for
-- scripted and dynamic actors the mod re-spawns on map.entered.
function WorldAPI:spawnNpc(mapId, objDef)
  local ow = self:overworld()
  if not ow then return nil, NO_OVERWORLD end
  if type(objDef) ~= "table" then return nil, "objDef must be a table" end
  local copy = {}
  for k, v in pairs(objDef) do copy[k] = v end
  return ow:addRuntimeObject(mapId, copy, self.modId)
end

function WorldAPI:removeNpc(npcId)
  local ow = self:overworld()
  if not ow then return nil, NO_OVERWORLD end
  return ow:removeRuntimeObject(npcId, self.modId)
end

-- a handle onto a live NPC: scriptMove / marchInPlace / face, which is
-- everything the scripted-movement queue exposes
local Handle = {}
Handle.__index = Handle

function Handle:scriptMove(dir, tiles, onDone)
  self.ow:scriptMove(self.npc, dir, tiles or 1, onDone)
  return true
end

function Handle:marchInPlace(onDone)
  self.ow:marchInPlace(self.npc, onDone)
  return true
end

function Handle:face(dir)
  self.npc.facing = dir
  return true
end

function Handle:position()
  return self.npc.cellX, self.npc.cellY
end

function WorldAPI:npc(mapId, indexOrName)
  local ow = self:overworld()
  if not ow then return nil, NO_OVERWORLD end
  if ow.map and ow.map.id ~= mapId then return nil, "map is not active" end
  for _, npc in ipairs(ow.npcs or {}) do
    if npc.def.index == indexOrName or npc.def.name == indexOrName
       or npc.id == indexOrName then
      return setmetatable({ ow = ow, npc = npc, id = npc.id }, Handle)
    end
  end
  return nil, "no such object: " .. tostring(indexOrName)
end

-- FIFO queueing is owned by the script runner; until it lands this runs
-- the rows when nothing else is running and refuses otherwise, so a mod
-- never silently loses a script.
function WorldAPI:queueScript(rows, extra)
  local ow = self:overworld()
  if not ow or not ow.runner then return nil, NO_OVERWORLD end
  if ow.runner:isRunning() then return nil, "a script is already running" end
  ow.runner:run(rows, extra)
  return true
end

-- drop a map's cached instance so the next load re-reads its record; when
-- it is the active map the world reloads around the player in place
function WorldAPI:invalidateMap(mapId)
  local ow = self:overworld()
  if not ow then
    local had = MapLoader.invalidate(mapId)
    Runtime.emit("map.reloaded", { mapId = mapId, reason = "invalidate" })
    return had
  end
  local ok, err = pcall(ow.reloadMap, ow, mapId, "invalidate")
  if not ok then
    Logger.warn("[%s] invalidateMap %s failed: %s", tostring(self.modId),
                tostring(mapId), tostring(err))
    return nil, tostring(err)
  end
  return true
end

return WorldAPI