import { RomReader } from "./reader";
import { decompress } from "./lz";
import {
  LAST_MAP_GROUP_SIZE,
  MAP_GROUP_COUNT,
  NATIVE_MAPS,
  NUM_ENGINE_FLAGS,
  NUM_SPRITEMOVEDATA,
  OVERWORLD,
  RAM,
  SYMBOLS,
} from "./profile";
import { defaultTextContext, readString } from "../scripts/text";
import { PokemonData } from "./pokemon";
import { OW } from "../world/constants";
import type {
  Direction,
  GameMap,
  Tileset,
  Palette,
  Sprite,
  FacingTile,
} from "../world/types";

/** The only layer that knows where Crystal stores its data. Everything is
 * decoded from the supplied ROM, on demand, and cached only in memory. */
export class CrystalAssets {
  readonly reader: RomReader;
  readonly pokemon: PokemonData;
  private maps = new Map<string, GameMap>();
  private tilesets = new Map<string, Tileset>();
  private sprites = new Map<number, Sprite>();
  private spawnFlags?: Map<number, number>;
  private sceneOwners?: Map<string, string>;
  constructor(bytes: Uint8Array) {
    this.reader = new RomReader(bytes);
    this.pokemon = new PokemonData(this.reader);
  }

  /** Areas whose rules and scripts are ported. Other maps can be decoded,
   * for example to draw a connected border, but cannot be entered. */
  isPorted(id: string): boolean {
    return Object.hasOwn(NATIVE_MAPS, id);
  }

  /** Header offset for a map ID, bounded by the ROM's own group table. */
  private header(id: string): number {
    const match = /^(\d{1,2}):(\d{1,3})$/.exec(id);
    const group = Number(match?.[1]),
      number = Number(match?.[2]);
    if (!match || group < 1 || group > MAP_GROUP_COUNT || number < 1)
      throw new Error("Unknown map.");
    const r = this.reader,
      bank = r.bank(SYMBOLS.mapGroups);
    const first = r.near(SYMBOLS.mapGroups + (group - 1) * 2, bank);
    const count =
      group === MAP_GROUP_COUNT
        ? LAST_MAP_GROUP_SIZE
        : (r.near(SYMBOLS.mapGroups + group * 2, bank) - first) / 9;
    if (number > count) throw new Error("Unknown map.");
    return first + (number - 1) * 9;
  }

  /** The location name the game shows for a landmark, from the ROM. */
  landmark(index: number): string {
    const r = this.reader,
      entry = SYMBOLS.landmarks + index * 4;
    const name = readString(
      r,
      r.near(entry + 2, r.bank(SYMBOLS.landmarks)),
      defaultTextContext(""),
    );
    return name
      .toLowerCase()
      .replace(
        /(^|[\s.-])(\p{L})/gu,
        (_, gap, letter) => gap + letter.toUpperCase(),
      );
  }

  /** The map that owns a map's scene variable (data/maps/scenes.asm). */
  sceneOwner(id: string): string | undefined {
    if (!this.sceneOwners) {
      const owners = new Map<string, string>(),
        byAddress = new Map<number, string>();
      const r = this.reader;
      for (let p = SYMBOLS.mapScenes, i = 0; i < 256; i++, p += 4) {
        const group = r.byte(p);
        if (group === 0xff) break;
        const map = `${group}:${r.byte(p + 1)}`,
          address = r.word(p + 2);
        const owner = byAddress.get(address) ?? map;
        byAddress.set(address, owner);
        owners.set(map, owner);
      }
      this.sceneOwners = owners;
    }
    return this.sceneOwners.get(id);
  }

  map(id: string): GameMap {
    const cached = this.maps.get(id);
    if (cached) return cached;
    const header = this.header(id);
    const [group, number] = id.split(":").map(Number);
    const r = this.reader;
    const attributes = r.near(header + 3, r.byte(header));
    const blockWidth = r.byte(attributes + 2),
      blockHeight = r.byte(attributes + 1);
    if (!blockWidth || !blockHeight || blockWidth > 64 || blockHeight > 64)
      throw new Error("Invalid map dimensions.");
    const scriptBank = r.byte(attributes + 6);
    let p = r.near(attributes + 9, scriptBank) + 2;
    const location = this.landmark(r.byte(header + 5));
    const map: GameMap = {
      id,
      group,
      number,
      name: NATIVE_MAPS[id] ?? location,
      location,
      landmark: r.byte(header + 5),
      width: blockWidth * 2,
      height: blockHeight * 2,
      border: r.byte(attributes),
      tileset: r.byte(header + 1),
      environment: r.byte(header + 2),
      paletteMode: r.byte(header + 7) & 15,
      phoneService: r.byte(header + 7) >> 4,
      attributes,
      blocks: r.slice(r.far(attributes + 3), blockWidth * blockHeight),
      warps: [],
      backgroundEvents: [],
      objects: [],
      connections: [],
      sceneScripts: [],
      callbacks: [],
      coordinateEvents: [],
    };
    const warpCount = r.byte(p++);
    for (let i = 0; i < warpCount; i++, p += 5) {
      map.warps.push({
        y: r.byte(p),
        x: r.byte(p + 1),
        targetWarp: r.byte(p + 2),
        targetMap: `${r.byte(p + 3)}:${r.byte(p + 4)}`,
      });
    }
    const coordinateCount = r.byte(p++);
    for (let i = 0; i < coordinateCount; i++, p += 8) {
      map.coordinateEvents.push({
        scene: r.byte(p),
        y: r.byte(p + 1),
        x: r.byte(p + 2),
        script: r.near(p + 4, scriptBank),
      });
    }
    const backgroundCount = r.byte(p++);
    for (let i = 0; i < backgroundCount; i++, p += 5) {
      map.backgroundEvents.push({
        y: r.byte(p),
        x: r.byte(p + 1),
        kind: r.byte(p + 2),
        script: r.near(p + 3, scriptBank),
      });
    }
    const objectCount = r.byte(p++);
    for (let i = 0; i < objectCount; i++, p += 13) {
      map.objects.push({
        id: i + 2,
        sprite: r.byte(p),
        y: r.byte(p + 1) - 4,
        x: r.byte(p + 2) - 4,
        movement: r.byte(p + 3),
        radius: r.byte(p + 4),
        sightRange: r.byte(p + 8),
        hour1: r.byte(p + 5),
        hour2: r.byte(p + 6),
        palette: r.byte(p + 7) >> 4,
        kind: r.byte(p + 7) & 15,
        script: r.near(p + 9, scriptBank),
        eventFlag: r.word(p + 11),
      });
    }
    p = r.near(attributes + 7, scriptBank);
    const sceneCount = r.byte(p++);
    for (let i = 0; i < sceneCount; i++, p += 4)
      map.sceneScripts.push(r.near(p, scriptBank));
    const callbackCount = r.byte(p++);
    for (let i = 0; i < callbackCount; i++, p += 3)
      map.callbacks.push({
        kind: r.byte(p),
        script: r.near(p + 1, scriptBank),
      });
    p = attributes + 12;
    for (const [direction, bit] of [
      ["up", 8],
      ["down", 4],
      ["left", 2],
      ["right", 1],
    ] as const) {
      if (!(r.byte(attributes + 11) & bit)) continue;
      const signed = (v: number) => (v > 127 ? v - 256 : v);
      map.connections.push({
        direction,
        targetMap: `${r.byte(p)}:${r.byte(p + 1)}`,
        y: signed(r.byte(p + 8)),
        x: signed(r.byte(p + 9)),
      });
      p += 12;
    }
    this.maps.set(id, map);
    return map;
  }

  tileset(map: GameMap): Tileset {
    const key = `${map.tileset}:${map.group}`;
    const cached = this.tilesets.get(key);
    if (cached) return cached;
    const r = this.reader,
      base = SYMBOLS.tilesets + map.tileset * 15;
    const graphics = decompress(r, r.far(base), 0x4000);
    const meta = r.far(base + 3),
      collision = r.far(base + 6);
    // Each tileset contains 128 metatiles (4x4 8px tiles), each with four
    // quadrant permissions for the 16px movement grid.
    const result: Tileset = {
      graphics,
      metatiles: r.slice(meta, 128 * 16),
      collision: r.slice(collision, 128 * 4),
      paletteMap: r.slice(r.near(base + 13, r.bank(SYMBOLS.tilesets)), 128),
    };
    if ([1, 2, 4].includes(map.tileset)) {
      const roof = r.byte(SYMBOLS.roofTypes + map.group);
      if (roof !== 255)
        result.graphics.set(
          r.slice(SYMBOLS.roofs + roof * 9 * 16, 9 * 16),
          0x0a * 16,
        );
    }
    this.tilesets.set(key, result);
    return result;
  }

  block(map: GameMap, x: number, y: number): number {
    if (x < 0 || y < 0 || x >= map.width || y >= map.height) return map.border;
    return map.blocks[Math.floor(y / 2) * (map.width / 2) + Math.floor(x / 2)];
  }
  /** Where a step coordinate outside `map` lands in a connected map. */
  connected(
    map: GameMap,
    x: number,
    y: number,
  ): { map: GameMap; x: number; y: number } | undefined {
    const direction =
      y < 0
        ? "up"
        : y >= map.height
          ? "down"
          : x < 0
            ? "left"
            : x >= map.width
              ? "right"
              : undefined;
    // Corners are outside every connection strip and show border blocks.
    if (!direction || ((x < 0 || x >= map.width) && (y < 0 || y >= map.height)))
      return undefined;
    const connection = map.connections.find((c) => c.direction === direction);
    if (!connection) return undefined;
    const target = this.map(connection.targetMap);
    // Offsets are the coordinates EnterMapConnection assigns on crossing.
    const position =
      direction === "up"
        ? { x: x + connection.x, y: y + 1 + connection.y }
        : direction === "down"
          ? { x: x + connection.x, y: y - map.height + connection.y }
          : direction === "left"
            ? { x: x + 1 + connection.x, y: y + connection.y }
            : { x: x - map.width + connection.x, y: y + connection.y };
    if (
      position.x < 0 ||
      position.y < 0 ||
      position.x >= target.width ||
      position.y >= target.height
    )
      return undefined;
    return { map: target, ...position };
  }
  /** A visible block, drawing connected maps beyond the edges as the
   * original connection strips do, with the current map's tileset. */
  visibleBlock(map: GameMap, x: number, y: number): number {
    if (x >= 0 && y >= 0 && x < map.width && y < map.height)
      return this.block(map, x, y);
    const target = this.connected(map, x, y);
    return target ? this.block(target.map, target.x, target.y) : map.border;
  }
  collision(map: GameMap, x: number, y: number): number {
    if (x < 0 || y < 0 || x >= map.width || y >= map.height) return 7;
    const block = this.block(map, x, y);
    if (block >= 128) throw new Error("Map contains an invalid block.");
    return this.tileset(map).collision[block * 4 + (y % 2) * 2 + (x % 2)];
  }
  permission(collision: number): number {
    return this.reader.byte(SYMBOLS.collisions + collision) & 15;
  }

  palette(offset: number): Palette {
    return Array.from({ length: 4 }, (_, i) => {
      const color = this.reader.word(offset + i * 2);
      return [
        Math.round(((color & 31) * 255) / 31),
        Math.round((((color >> 5) & 31) * 255) / 31),
        Math.round((((color >> 10) & 31) * 255) / 31),
      ];
    });
  }
  /** LoadSpecialMapPalette: tilesets with their own eight palettes, which
   * do not follow the time of day. */
  private specialPalettes(map: GameMap): Palette[] | undefined {
    const eight = (address: number) =>
      Array.from({ length: 8 }, (_, i) => this.palette(address + i * 8));
    switch (map.tileset) {
      case OW.TILESET_POKECOM_CENTER:
        return eight(OVERWORLD.PokeComPalette);
      case OW.TILESET_BATTLE_TOWER_INSIDE:
        return eight(OVERWORLD.BattleTowerInsidePalette);
      case OW.TILESET_ICE_PATH:
        // The Hall of Fame shares the tileset but is INDOOR.
        return (map.environment & 7) === OW.INDOOR ? undefined : eight(OVERWORLD.IcePathPalette);
      case OW.TILESET_HOUSE:
        return eight(SYMBOLS.housePalettes);
      case OW.TILESET_RADIO_TOWER:
        return eight(OVERWORLD.RadioTowerPalette);
      case OW.TILESET_MANSION: {
        // LoadMansionPalette: MansionPalette1, then yellow from
        // MansionPalette2, water from palette 6 and roof from palette 8.
        const palettes = eight(OVERWORLD.MansionPalette1);
        palettes[4] = this.palette(OVERWORLD.MansionPalette2);
        palettes[3] = this.palette(OVERWORLD.MansionPalette1 + 6 * 8);
        palettes[6] = this.palette(OVERWORLD.MansionPalette1 + 8 * 8);
        return palettes;
      }
    }
    return undefined;
  }
  palettes(map: GameMap, time: number): Palette[] {
    const r = this.reader;
    const group =
      r.near(
        SYMBOLS.environmentColors + map.environment * 2,
        r.bank(SYMBOLS.environmentColors),
      ) +
      time * 8;
    const palettes =
      this.specialPalettes(map) ??
      Array.from({ length: 8 }, (_, i) =>
        this.palette(SYMBOLS.backgroundPalettes + r.byte(group + i) * 8),
      );
    if (map.environment === 1 || map.environment === 2) {
      const roof = SYMBOLS.roofPalettes + map.group * 8 + (time >= 2 ? 4 : 0);
      const colors = this.palette(roof);
      palettes[6] = [palettes[6][0], colors[0], colors[1], palettes[6][3]];
    }
    return palettes;
  }
  objectPalette(index: number, time: number): Palette {
    return this.palette(SYMBOLS.objectPalettes + time * 64 + (index & 7) * 8);
  }
  /** Collisions that allow wild encounters (CheckGrassCollision). */
  grassCollisions(): number[] {
    const r = this.reader,
      values: number[] = [];
    for (let p = SYMBOLS.grassCollisions; values.length < 32; p++) {
      const value = r.byte(p);
      if (value === 0xff) return values;
      values.push(value);
    }
    throw new Error("Grass collision list is unterminated.");
  }
  /** JohtoGrassWildMons or KantoGrassWildMons for a map: encounter rates
   * and seven slots per time of day (data/wild/johto_grass.asm). */
  grassWildMons(
    id: string,
    kanto = false,
  ): { rates: number[]; slots: { level: number; species: number }[][] } | undefined {
    const r = this.reader;
    const table = kanto ? OVERWORLD.KantoGrassWildMons : SYMBOLS.johtoGrassWildMons;
    for (let p = table, i = 0; i < 256; i++, p += 47) {
      const group = r.byte(p);
      if (group === 0xff) return undefined;
      if (`${group}:${r.byte(p + 1)}` !== id) continue;
      const rates = [r.byte(p + 2), r.byte(p + 3), r.byte(p + 4)];
      const slots = [0, 1, 2].map((time) =>
        Array.from({ length: 7 }, (_, slot) => {
          const entry = p + 5 + time * 14 + slot * 2;
          return { level: r.byte(entry), species: r.byte(entry + 1) };
        }),
      );
      return { rates, slots };
    }
    throw new Error("Wild encounter data is unterminated.");
  }
  /** JohtoWaterWildMons or KantoWaterWildMons: one rate and three slots
   * (data/wild/johto_water.asm). */
  waterWildMons(
    id: string,
    kanto = false,
  ): { rate: number; slots: { level: number; species: number }[] } | undefined {
    const r = this.reader;
    const table = kanto ? OVERWORLD.KantoWaterWildMons : OVERWORLD.JohtoWaterWildMons;
    for (let p = table, i = 0; i < 256; i++, p += 9) {
      const group = r.byte(p);
      if (group === 0xff) return undefined;
      if (`${group}:${r.byte(p + 1)}` !== id) continue;
      return {
        rate: r.byte(p + 2),
        slots: Array.from({ length: 3 }, (_, slot) => ({
          level: r.byte(p + 3 + slot * 2),
          species: r.byte(p + 4 + slot * 2),
        })),
      };
    }
    throw new Error("Wild encounter data is unterminated.");
  }
  /** Engine flags kept in the four bytes CheckDailyResetTimer clears
   * (wDailyFlags1 through wUnusedDailyFlag), from the ROM's EngineFlags. */
  dailyEngineFlags(): number[] {
    const r = this.reader,
      flags: number[] = [];
    for (let index = 0; index < NUM_ENGINE_FLAGS; index++) {
      const address = r.word(SYMBOLS.engineFlags + index * 3);
      if (address >= RAM.dailyFlags1 && address <= RAM.unusedDailyFlag)
        flags.push(index);
    }
    return flags;
  }
  /** The engine flag (ENGINE_FLYPOINT_*) of a wVisitedSpawns bit, from the
   * ROM's EngineFlags; undefined for spawn points without one. */
  spawnEngineFlag(spawn: number): number | undefined {
    if (!this.spawnFlags) {
      const r = this.reader;
      this.spawnFlags = new Map();
      for (let index = 0; index < NUM_ENGINE_FLAGS; index++) {
        const entry = SYMBOLS.engineFlags + index * 3,
          offset = r.word(entry) - RAM.visitedSpawns,
          mask = r.byte(entry + 2);
        if (offset >= 0 && offset < 4)
          this.spawnFlags.set(offset * 8 + Math.log2(mask), index);
      }
    }
    return this.spawnFlags.get(spawn);
  }
  /** SpawnPoints: a SPAWN_* point's map and position. */
  spawnPoint(spawn: number): { map: string; x: number; y: number } {
    const r = this.reader,
      entry = SYMBOLS.spawnPoints + spawn * 4;
    return {
      map: `${r.byte(entry)}:${r.byte(entry + 1)}`,
      x: r.byte(entry + 2),
      y: r.byte(entry + 3),
    };
  }
  /** IsSpawnPoint: the SPAWN_* index of a map, or -1. */
  spawnIndex(map: string | null): number {
    const r = this.reader;
    if (map)
      for (
        let entry = SYMBOLS.spawnPoints, index = 0;
        r.byte(entry) !== 0xff;
        entry += 4, index++
      )
        if (`${r.byte(entry)}:${r.byte(entry + 1)}` === map) return index;
    return -1;
  }
  /** SpriteMovementData for a SPRITEMOVEDATA_* type: the movement
   * function, flags1 (FIXED_FACING, NOCLIP_*, ...) and palette flags. */
  spriteMovement(type: number): {
    fn: number;
    /** OBJECT_ACTION_* the object starts with. */
    action: number;
    flags: number;
    paletteFlags: number;
  } {
    if (type >= NUM_SPRITEMOVEDATA) throw new Error("Unknown movement type.");
    const r = this.reader,
      p = SYMBOLS.spriteMovementData + type * 6;
    return {
      fn: r.byte(p),
      action: r.byte(p + 2),
      flags: r.byte(p + 3),
      paletteFlags: r.byte(p + 5),
    };
  }
  /** Emote bubble graphics (data/sprites/emotes.asm). */
  emote(index: number): Uint8Array {
    const r = this.reader,
      entry = SYMBOLS.emotes + index * 6;
    if (index < 0 || index > 11) throw new Error("Unknown emote.");
    return r.slice(
      r.address(r.byte(entry + 3), r.word(entry)),
      r.byte(entry + 2),
    );
  }
  /** HeadbuttTreeGFX: the shaking tree's two 2x2 frames, eight tiles. */
  headbuttTree(): Uint8Array {
    return this.reader.slice(OVERWORLD.HeadbuttTreeGFX, 8 * 16);
  }
  /** GetIcon: a species' two-frame party menu icon (ReadMonMenuIcon and
   * IconPointers), eight tiles. */
  monIcon(species: number): Uint8Array {
    const r = this.reader;
    const icon = r.byte(OVERWORLD.MonMenuIcons + species - 1);
    const pointer = r.near(
      OVERWORLD.IconPointers + icon * 2,
      r.bank(OVERWORLD.IconPointers),
    );
    return r.slice(pointer, 8 * 16);
  }
  /** GetSprite: overworld sprites, and Pokémon drawn from their party
   * menu icons (GetMonSprite). Variable sprites are resolved by the world
   * from wVariableSprites first; day-care Pokémon are not ported. */
  sprite(id: number): Sprite | undefined {
    const cached = this.sprites.get(id);
    if (cached) return cached;
    const r = this.reader;
    if (id >= OW.SPRITE_POKEMON && id < OW.SPRITE_POKEMON + OW.NUM_POKEMON_SPRITES) {
      // LoadOverworldMonIcon: eight tiles, two frames in the down and up
      // standing slots, with palette 0.
      const species = r.byte(OVERWORLD.SpriteMons + id - OW.SPRITE_POKEMON);
      const sprite = { graphics: this.monIcon(species), palette: 0, walking: true };
      this.sprites.set(id, sprite);
      return sprite;
    }
    if (id < 1 || id > OW.NUM_OVERWORLD_SPRITES) return undefined;
    const p = SYMBOLS.sprites + (id - 1) * 6;
    const length = r.byte(p + 2),
      walking = r.byte(p + 4) === 1;
    const sprite = {
      graphics: r.slice(r.near(p, r.byte(p + 3)), length * (walking ? 2 : 1)),
      palette: r.byte(p + 5),
      walking,
    };
    this.sprites.set(id, sprite);
    return sprite;
  }
  facing(direction: Direction, frame: number): FacingTile[] {
    return this.facingTiles(
      ["down", "up", "left", "right"].indexOf(direction) * 4 + (frame % 4),
    );
  }
  /** FACING_* layouts; 0x14 is the emote bubble. */
  facingTiles(facing: number): FacingTile[] {
    const r = this.reader,
      pointer = r.near(SYMBOLS.facings + facing * 2, r.bank(SYMBOLS.facings));
    return Array.from({ length: r.byte(pointer) }, (_, i) => {
      const p = pointer + 1 + i * 4;
      return {
        y: r.byte(p),
        x: r.byte(p + 1),
        attributes: r.byte(p + 2),
        tile: r.byte(p + 3),
      };
    });
  }
}