import {
  calculate,
  toID,
  Field,
  Generations,
  Move,
  Pokemon,
  Result,
} from "@ajhyndman/smogon-calc";
import assert from "assert";
import { createToken, Lexer } from "chevrotain";

const gen = Generations.get(9);

/**
 * Creates a lexer.
 *
 * @returns {Lexer}
 */
function buildLexer() {
  const Boost = createToken({ name: "Boost", pattern: /[+-]\d+/ });
  const EV = createToken({ name: "EV", pattern: /\d+[+-]?/ });
  const Stat = createToken({
    name: "Stat",
    pattern: /HP|Atk|Def|SpA|SpD|Spe/,
  });

  const Item = createToken({
    name: "Item",
    pattern: new RegExp([...gen.items].map((i) => i.name).join("|")),
  });
  const Ability = createToken({
    name: "Ability",
    pattern: new RegExp([...gen.abilities].map((a) => a.name).join("|")),
  });

  const Pokemon = createToken({
    name: "Pokemon",
    pattern: new RegExp([...gen.species].map((s) => s.name).join("|")),
  });
  const Move = createToken({
    name: "Move",
    pattern: new RegExp([...gen.moves].map((m) => m.name).join("|")),
  });

  const whitespace = createToken({
    name: "Whitespace",
    pattern: /\s+/,
    group: Lexer.SKIPPED,
  });
  const div = createToken({
    name: "div",
    pattern: "/",
    group: Lexer.SKIPPED,
  });
  const vs = createToken({
    name: "vs",
    pattern: /vs\.?/,
  });

  const terrainEnter = createToken({
    name: "terrainEnter",
    pattern: "in",
    push_mode: "terrain_mode",
  });
  const Weather = createToken({
    name: "Weather",
    pattern: /Sun|Rain|Sand|Snow/,
  });
  const Terrain = createToken({
    name: "Terrain",
    pattern: /(Electric|Grassy|Misty|Psychic) Terrain/,
  });

  const screenEnter = createToken({
    name: "screenEnter",
    pattern: "through",
    push_mode: "screen_mode",
  });

  return new Lexer({
    modes: {
      default_mode: [
        whitespace,
        div,
        vs,
        Boost,
        EV,
        Stat,
        Item,
        Ability,
        Pokemon,
        Move,
        terrainEnter,
        screenEnter,
      ],
      terrain_mode: [whitespace, screenEnter, Weather, Terrain],
      screen_mode: [whitespace, Move],
    },
    defaultMode: "default_mode",
  });
}

/**
 * @generator
 * @template T item type
 * @param {T[]} arr
 * @yields {T} item
 */
function* iterate(arr) {
  for (const a of arr) {
    yield a;
  }
}

/**
 * @param {string} type token type
 * @param {import("chevrotain").IToken} token token
 * @return {string} matched token
 */
function unwrapToken(type, token) {
  assert(
    token.tokenType.name == type,
    `expected token ${type}, got ${token.tokenType.name}`,
  );
  return token.image;
}

const POS_NATURES = {
  atk: "Adamant",
  def: "Bold",
  spa: "Modest",
  spd: "Calm",
  spe: "Jolly",
};

const NEG_NATURES = {
  atk: "Modest",
  def: "Lonely",
  spa: "Adamant",
  spd: "Rash",
  spe: "Brave",
};

/**
 * Parses a Smogon calculator output:
 *
 * -2 8 SpA Choice Specs Torkoal vs.
 * 252 HP / 4+ SpD Assault Vest Abomasnow
 * in Sun
 * through Light Screen
 *
 * @param {string} line textual line
 * @return {Result} calculation result
 */
function parseAndCalculate(line) {
  const lexer = buildLexer();
  const result = lexer.tokenize(line);
  if (result.errors && result.errors.length > 0) {
    console.error("Unparsed tokens: %o", result.errors);
  }

  /** @type {string} */
  var attacker;
  /** @type {string} */
  var defender;

  /** @type {import("@ajhyndman/smogon-calc").State.Pokemon} */
  var attackerOpts = {};
  /** @type {import("@ajhyndman/smogon-calc").State.Pokemon} */
  var defenderOpts = {};

  /** @type {string} */
  var move;
  /** @type {import("@ajhyndman/smogon-calc").State.Field} */
  var field = {};

  // Tokenising state.
  var isAttacker = true;
  var it = iterate(result.tokens);

  const opts = () => (isAttacker ? attackerOpts : defenderOpts);

  while (true) {
    let item = it.next().value;
    if (!item) break;
    switch (item.tokenType.name) {
      case "Boost":
        {
          let boost = unwrapToken("Boost", item);
          let ev = unwrapToken("EV", it.next().value);
          let stat = unwrapToken("Stat", it.next().value).toLowerCase();
          opts().boosts = { [stat]: parseInt(boost), ...opts().boosts };
          opts().evs = { [stat]: parseInt(ev), ...opts().evs };
          if (ev.endsWith("+")) {
            opts().nature = POS_NATURES[stat];
          } else if (ev.endsWith("-")) {
            opts().nature = NEG_NATURES[stat];
          }
        }
        break;
      case "EV":
        {
          let ev = unwrapToken("EV", item);
          let stat = unwrapToken("Stat", it.next().value).toLowerCase();
          opts().evs = { [stat]: parseInt(ev), ...opts().evs };
          if (ev.endsWith("+")) {
            opts().nature = POS_NATURES[stat];
          } else if (ev.endsWith("-")) {
            opts().nature = NEG_NATURES[stat];
          }
        }
        break;
      case "Stat":
        throw Error("Impossible state: bare Stat");
      case "Item":
        opts().item = unwrapToken("Item", item);
        break;
      case "Ability":
        opts().ability = unwrapToken("Ability", item);
        break;
      case "Pokemon":
        {
          let name = unwrapToken("Pokemon", item);
          if (isAttacker) attacker = name;
          else defender = name;
        }
        break;
      case "Move":
        move = unwrapToken("Move", item);
        break;
      case "terrainEnter":
        {
          let next = it.next().value;
          switch (next.tokenType.name) {
            case "Weather":
              field.weather = next.image;
              break;
            case "Terrain":
              field.terrain = next.image;
              break;
            default:
              throw Error(
                "Unhandled terrain %s: %s",
                next.tokenType.name,
                next.image
              );
          }
        }
        break;
      case "screenEnter":
        {
          let screen = unwrapToken("Move", it.next().value);
          field.defenderSide = field.defenderSide || {};
          field.defenderSide.isLightScreen = screen === "Light Screen";
          field.defenderSide.isReflect = screen === "Reflect";
          field.defenderSide.isAuroraVeil = screen === "Aurora Veil";
          field.defenderSide.is;
        }
        break;
      case "vs":
        isAttacker = false;
        break;
      default:
        console.error("unmatched token type: %s", item.tokenType.name);
        break;
    }
  }

  // Pre-checking before the calculator throws unreadable errors.
  if (!gen.species.get(toID(attacker)))
    throw Error(`No species named ${attacker}`);
  if (!gen.species.get(toID(defender)))
    throw Error(`No species named ${defender}`);
  if (!gen.moves.get(toID(move))) throw Error(`No move named ${move}`);

  return calculate(
    gen,
    new Pokemon(gen, attacker, attackerOpts),
    new Pokemon(gen, defender, defenderOpts),
    new Move(gen, move),
    new Field(field)
  );
}

function test() {
  const text =
    "-2 8 SpA Choice Specs Torkoal Overheat vs. 252 HP / 4+ SpD Assault Vest Abomasnow in Sun through Light Screen";
  const res = parseAndCalculate(text);

  assert(res.attacker.boosts.spa === -2, "should have -2 SpA");
  assert(res.attacker.evs.spa === 8, "should have 8 SpA EVs");
  assert(res.attacker.item === "Choice Specs", "should have Choice Specs");
  assert(res.attacker.name === "Torkoal", "should be Torkoal");
  assert(res.move.name === "Overheat", "should be Overheat");
  assert(res.defender.evs.hp === 252, "should have 252 HP EVs");
  assert(res.defender.evs.spd === 4, "should have 4 SpD EVs");
  assert(res.field.weather === "Sun", "should be in sun");

  assert(
    res.desc().replace(/:.*/, "") === text,
    "non-damage text should be equivalent to input"
  );
}

export { parseAndCalculate, test };