-- Read-only Gen 1 battle state for companion UIs and accessibility mods.

local Damage = require("src.battle.Damage")
local ItemEffects = require("src.inventory.ItemEffects")
local TypeChart = require("src.battle.TypeChart")

local BattleAPI = {}
BattleAPI.__index = BattleAPI

function BattleAPI.new(game)
  return setmetatable({ game = game, revision = 0, signature = nil }, BattleAPI)
end

local function activeBattle(game)
  local states = game and game.stack and game.stack.states or {}
  for i = #states, 1, -1 do
    if states[i].isBattleState then return states[i], states[#states] end
  end
end

local function monCopy(data, mon, active)
  if not mon then return nil end
  local def = data.pokemon[mon.species]
  return {
    species = mon.species,
    name = mon.nickname or (def and def.name) or mon.species,
    level = mon.level, hp = mon.hp,
    maxHp = mon.stats and mon.stats.hp or mon.hp,
    status = mon.status, active = active and true or false,
  }
end

local function visibleMessage(battle, top)
  local source = top and top.isTextBox and top or top == battle and battle
  local lines = source and source.visibleText and source:visibleText()
  if not lines then return nil end
  local copy = {}
  for i, line in ipairs(lines) do copy[i] = tostring(line) end
  return copy
end

local function signature(game, battle, top)
  if not battle then return "none" end
  local parts = { tostring(battle), tostring(top), battle.phase or "",
    tostring(battle.turnCount or 0), tostring(#(battle.queue or {})),
    tostring(battle.current), tostring(battle.msgWaiting),
    tostring(battle.msgPrompt), tostring(battle.menuIndex),
    tostring(battle.mimicIndex),
    tostring(battle.safari and battle.safari.balls),
    tostring(battle.ghost), tostring(battle.noCatch),
    table.concat(visibleMessage(battle, top) or {}, "\n") }
  for _, battler in ipairs({ battle.player, battle.enemy }) do
    local mon = battler and battler.mon
    parts[#parts + 1] = tostring(mon)
    parts[#parts + 1] = tostring(mon and mon.hp)
    parts[#parts + 1] = tostring(mon and mon.status)
    parts[#parts + 1] = table.concat(battler and battler.curTypes or {}, ",")
  end
  for _, mon in ipairs(game.save.party or {}) do
    parts[#parts + 1] = tostring(mon)
    parts[#parts + 1] = tostring(mon.hp)
    parts[#parts + 1] = tostring(mon.status)
  end
  local inventory = {}
  for id, count in pairs(game.save.inventory or {}) do
    if ItemEffects.isBall(id) or ItemEffects.isBattleMedicine(id) then
      inventory[#inventory + 1] = id .. "=" .. tostring(count)
    end
  end
  table.sort(inventory)
  for _, item in ipairs(inventory) do parts[#parts + 1] = item end
  return table.concat(parts, "|")
end

function BattleAPI:_revision(battle, top)
  local nextSignature = signature(self.game, battle, top)
  if nextSignature ~= self.signature then
    self.signature = nextSignature
    self.revision = self.revision + 1
  end
  return self.revision
end

local IMMUNITY_ONLY = { SPECIAL_DAMAGE_EFFECT = true,
  SUPER_FANG_EFFECT = true, OHKO_EFFECT = true }

local function movePreview(battle, move, def)
  local record = battle.effectRecord and battle:effectRecord(def.effect)
  local power, typeMult = def.power or 0
  if power > 0 and move.id ~= "COUNTER" then
    local raw = TypeChart.effectiveness(def.type, battle.enemy.curTypes or {})
    if IMMUNITY_ONLY[def.effect] then
      typeMult = raw == 0 and 0 or 10
    elseif not (record and record.chooseDamage) then
      typeMult = raw
    end
  end
  local hitChance
  if record and record.neverMiss then
    hitChance = 100
  elseif not (record and record.gate)
      and (power > 0 or (record and record.accuracyChecked)) then
    hitChance = battle.enemy.invulnerable and 0
      or Damage.accuracyChance(battle.ruleset, def,
        battle.player, battle.enemy)
  end
  local displayPower = power > 0 and move.id ~= "COUNTER"
    and not IMMUNITY_ONLY[def.effect]
    and not (record and record.chooseDamage) and power or nil
  return typeMult, hitChance, displayPower
end

local function moveCopies(game, battle)
  local out = {}
  for slot, move in ipairs((battle.player and battle.player.curMoves) or {}) do
    local def = game.data.moves[move.id] or {}
    local mult, hitChance, displayPower = movePreview(battle, move, def)
    out[slot] = { slot = slot, id = move.id, name = def.name or move.id,
      pp = move.pp,
      maxPp = (def.pp or move.pp or 0)
        + (move.ppUps or 0) * math.floor((def.pp or 0) / 5),
      type = def.type, power = def.power, accuracy = def.accuracy,
      displayPower = displayPower, hitChance = hitChance,
      effectiveness = mult,
      disabled = battle.player.disabledSlot == slot }
  end
  return out
end

local function itemCopies(game, battle, catchable)
  local out = {}
  for id, count in pairs(game.save.inventory or {}) do
    if count > 0
        and (ItemEffects.isBall(id) or ItemEffects.isBattleMedicine(id)) then
      local def = game.data.items[id] or {}
      local ball = ItemEffects.isBall(id)
      out[#out + 1] = { id = id, name = def.name or id, count = count,
        ball = ball, needsTarget = not ball,
        catchChance = ball and catchable and battle.catchChance
          and battle:catchChance(id) or nil }
    end
  end
  table.sort(out, function(a, b) return a.name < b.name end)
  return out
end

local function mimicCopies(game, battle)
  local out = {}
  for i, move in ipairs(battle.mimicMoves or {}) do
    local def = game.data.moves[move.id] or {}
    out[i] = { index = i, slot = move.slot, id = move.id,
      name = def.name or move.id }
  end
  return out
end

function BattleAPI:snapshot()
  local game = self.game
  local battle, top = activeBattle(game)
  if not battle then return nil end
  local kind = battle:battleKind()
  local supported = kind ~= "oldman" and kind ~= "link"
  local catchable = kind == "wild" and not battle.ghost and not battle.noCatch
  local forcedParty = top and top.isPartyMenu and top.battle == battle
    and top.forceSwitch
  local canAdvance = supported and ((top == battle
      and battle.phase == "messages" and battle.current
      and (battle.msgWaiting or battle.msgPrompt))
    or (top and top.isTextBox and not top.choice
      and (top.waiting or top.done)))
  local prompt = "locked"
  if canAdvance then prompt = "advance"
  elseif supported and forcedParty then prompt = "party"
  elseif supported and top == battle and kind == "safari"
      and battle.phase == "menu" then prompt = "safari"
  elseif supported and top == battle and battle.phase == "mimicSelect" then
    prompt = "mimic"
  elseif supported and top == battle and battle.phase == "menu" then
    prompt = "menu"
  elseif supported and top == battle and battle.phase == "moveSelect" then
    prompt = "moves"
  end
  local party = {}
  for i, mon in ipairs(game.save.party or {}) do
    party[i] = monCopy(game.data, mon,
      battle.player and battle.player.mon == mon)
    party[i].slot = i
  end
  return { revision = self:_revision(battle, top), kind = kind,
    catchable = catchable, prompt = prompt,
    message = visibleMessage(battle, top), turn = battle.turnCount or 0,
    player = monCopy(game.data, battle.player and battle.player.mon, true),
    enemy = monCopy(game.data, battle.enemy and battle.enemy.mon, true),
    party = party, moves = moveCopies(game, battle),
    items = itemCopies(game, battle, catchable),
    safariBalls = battle.safari and battle.safari.balls or nil,
    mimicMoves = mimicCopies(game, battle), mimicIndex = battle.mimicIndex }
end

local MENU_CHOICES = { fight = true, party = true, item = true, run = true }

local function validSlot(slot)
  return type(slot) == "number" and slot % 1 == 0 and slot >= 1
end

function BattleAPI:submit(intent)
  if type(intent) ~= "table" then return nil, "intent must be a table" end
  if type(intent.id) ~= "number" or intent.id % 1 ~= 0 or intent.id < 1 then
    return nil, "intent id must be a positive integer"
  end
  if self.lastIntentId and intent.id <= self.lastIntentId then
    return nil, "replayed intent"
  end

  local battle, top = activeBattle(self.game)
  if not battle then return nil, "no battle" end
  if intent.revision ~= self:_revision(battle, top) then
    return nil, "stale battle context"
  end
  local kind = battle:battleKind()
  if kind == "oldman" or kind == "link" then
    return nil, "battle kind is not controllable"
  end
  if top ~= battle then return nil, "battle menu is covered" end

  local ok, err
  if intent.kind == "safari" then
    if kind ~= "safari" then return nil, "safari menu is not active" end
    ok, err = battle:chooseSafari(intent.action)
  elseif kind == "safari" then
    return nil, "battle kind is not controllable"
  elseif intent.kind == "mimic" then
    ok, err = battle:chooseMimic(intent.index)
  elseif intent.kind == "menu" then
    if battle.phase ~= "menu" then return nil, "battle menu is not active" end
    if not MENU_CHOICES[intent.choice] then
      return nil, "unknown battle menu choice"
    end
    ok, err = battle:chooseMenu(intent.choice)
  elseif intent.kind == "move" then
    if battle.phase ~= "moveSelect" then
      return nil, "move menu is not active"
    end
    if battle.moveSwapIndex then return nil, "move reorder is active" end
    local move = validSlot(intent.slot) and battle.player
      and battle.player.curMoves[intent.slot]
    if not move then return nil, "invalid move slot" end
    if (move.pp or 0) <= 0 then return nil, "move has no PP" end
    if battle.player.disabledSlot == intent.slot then
      return nil, "move is disabled"
    end
    ok, err = battle:chooseMove(intent.slot)
  elseif intent.kind == "back" then
    ok, err = battle:cancelMove()
  else
    return nil, "unknown battle intent"
  end
  if not ok then return nil, err end
  self.lastIntentId = intent.id
  self.signature = nil
  return true
end

return BattleAPI