/**
 * Offline Missile Asset & Data Baking Script.
 *
 * Extracts authentic Diablo II v1.13c missile DCC sprites from d2data.mpq:
 * - Firebolt.dcc (16 directions, 5 frames per direction)
 * - Fireball.dcc (16 directions, 5 frames per direction)
 * - FireArrowExplode2.dcc (1 direction, 12 frames)
 *
 * Bakes them into indexed-color PNG atlases and JSON metadata under:
 * - public/missiles/
 * - samples/d2-packs/missiles/
 *
 * And generates typed metadata in src/render/missiles-meta.ts.
 * Enforces Zero Runtime MPQ/DLL Architectural Invariant.
 */

import { mkdirSync, writeFileSync } from 'node:fs'
import { join } from 'node:path'
import { MpqArchive } from '../src/mpq/archive.ts'
import { fileSource } from '../src/mpq/file-source.ts'
import { decodeDcc } from '../src/formats/dcc.ts'
import { decodePl2 } from '../src/formats/pl2.ts'
import { packSheetToPng } from './pack-entity-assets.ts'
import type { SpriteFrame, SpriteSheet } from '../src/formats/sprite.ts'

export interface MissileFrameMeta {
  readonly x: number
  readonly y: number
  readonly w: number
  readonly h: number
  readonly anchorX: number
  readonly anchorY: number
}

export type MissileFrameTuple = readonly [
  x: number,
  y: number,
  width: number,
  height: number,
  anchorX: number,
  anchorY: number,
]

export interface MissileMeta {
  readonly name: string
  readonly celFile: string
  readonly width: number
  readonly height: number
  readonly directions: number
  readonly framesPerDirection: number
  readonly animSpeed: number
  readonly groups: readonly (readonly MissileFrameTuple[])[]
}

const MISSILE_TARGETS = [
  { name: 'firebolt', celFile: 'Firebolt', animSpeed: 16 },
  { name: 'fireball', celFile: 'Fireball', animSpeed: 16 },
  { name: 'fireexplode', celFile: 'FireArrowExplode2', animSpeed: 16 },
] as const

export async function bakeMissiles(projectRoot: string = process.cwd()): Promise<Record<string, MissileMeta>> {
  const mpqPath = join(projectRoot, 'samples', 'd2', 'd2data.mpq')
  const mpq = await MpqArchive.open(await fileSource(mpqPath))

  const palFile = mpq.find('data/global/palette/ACT1/pal.pl2')
  if (!palFile) throw new Error('data/global/palette/ACT1/pal.pl2 not found in d2data.mpq')
  const pl2 = decodePl2(await mpq.read(palFile))

  const publicOutDir = join(projectRoot, 'public', 'missiles')
  const packOutDir = join(projectRoot, 'samples', 'd2-packs', 'missiles')
  mkdirSync(publicOutDir, { recursive: true })
  mkdirSync(packOutDir, { recursive: true })

  const metaRecord: Record<string, MissileMeta> = {}

  for (const target of MISSILE_TARGETS) {
    const f = mpq.find(`data/global/missiles/${target.celFile}.dcc`)
    if (!f) throw new Error(`Missile DCC not found: data/global/missiles/${target.celFile}.dcc`)

    const dcc = decodeDcc(await mpq.read(f))
    const groups = dcc.directions.map(dir => ({
      frames: dir.frames.map(
        (frame): SpriteFrame => ({
          width: frame.frame.width,
          height: frame.frame.height,
          indices: frame.frame.indices,
          mask: frame.frame.mask,
          anchorX: dir.box.left,
          anchorY: dir.box.top,
        }),
      ),
    }))

    const sheet: SpriteSheet = { groups, width: null }
    const packed = packSheetToPng(sheet, pl2.rgb)

    const meta: MissileMeta = {
      name: target.name,
      celFile: target.celFile,
      width: packed.width,
      height: packed.height,
      directions: dcc.directions.length,
      framesPerDirection: dcc.directions[0]?.frames.length ?? 0,
      animSpeed: target.animSpeed,
      groups: packed.groups,
    }

    metaRecord[target.name] = meta

    // Write PNG and JSON to public/missiles/ and samples/d2-packs/missiles/
    const jsonStr = JSON.stringify(meta, null, 2)
    writeFileSync(join(publicOutDir, `${target.name}.png`), packed.png)
    writeFileSync(join(publicOutDir, `${target.name}.json`), jsonStr, 'utf-8')
    writeFileSync(join(packOutDir, `${target.name}.png`), packed.png)
    writeFileSync(join(packOutDir, `${target.name}.json`), jsonStr, 'utf-8')

    console.log(`[Missile Packer] Baked ${target.name} (${target.celFile}.dcc): ${packed.width}x${packed.height}, ${packed.png.byteLength} bytes PNG`)
  }

  // Generate src/render/missiles-meta.ts
  const metaTsContent = `/**
 * Authentic Diablo II v1.13c Missile Atlas Metadata.
 * Auto-generated by scripts/pack-missiles.ts.
 * Enforces Zero Runtime MPQ/DLL Architectural Invariant.
 */

export interface MissileFrameMeta {
  readonly x: number
  readonly y: number
  readonly w: number
  readonly h: number
  readonly anchorX: number
  readonly anchorY: number
}

export type MissileFrameTuple = readonly [
  x: number,
  y: number,
  width: number,
  height: number,
  anchorX: number,
  anchorY: number,
]

export interface MissileMeta {
  readonly name: string
  readonly celFile: string
  readonly width: number
  readonly height: number
  readonly directions: number
  readonly framesPerDirection: number
  readonly animSpeed: number
  readonly groups: readonly (readonly MissileFrameTuple[])[]
}

/**
 * The engine's 64-direction space -> DCC direction tables.
 * Ported from OpenDiablo2 d2fileformats/d2dcc/dcc_dir_lookup.go (Dir64ToDcc).
 */
const DIR64_TO_DCC_16: readonly number[] = [
  4, 4, 8, 8, 8, 8, 0, 0, 0, 0, 9, 9, 9, 9, 5, 5,
  5, 5, 10, 10, 10, 10, 1, 1, 1, 1, 11, 11, 11, 11, 6, 6,
  6, 6, 12, 12, 12, 12, 2, 2, 2, 2, 13, 13, 13, 13, 7, 7,
  7, 7, 14, 14, 14, 14, 3, 3, 3, 3, 15, 15, 15, 15, 4, 4,
]

/**
 * Calculate DCC direction index for a missile based on 2D velocity vector.
 *
 * In Diablo II's 64-direction space:
 * - South (0, +y) is dir 0
 * - West (-x, 0) is dir 16
 * - North (0, -y) is dir 32
 * - East (+x, 0) is dir 48
 */
export function velocityToDccDirection(vx: number, vy: number, directions = 16): number {
  if (directions <= 1) return 0
  const angle = Math.atan2(vy, vx) // -PI to PI
  // Map angle so that South (PI/2) is 0, turning clockwise
  const fraction = (angle - Math.PI / 2) / (2 * Math.PI)
  const dir64 = Math.round((((fraction % 1) + 1) % 1) * 64) % 64
  if (directions === 16) {
    return DIR64_TO_DCC_16[dir64] ?? 0
  }
  return 0
}

export const FIREBOLT_META: MissileMeta = ${JSON.stringify(metaRecord['firebolt'], null, 2)}

export const FIREBALL_META: MissileMeta = ${JSON.stringify(metaRecord['fireball'], null, 2)}

export const FIREEXPLODE_META: MissileMeta = ${JSON.stringify(metaRecord['fireexplode'], null, 2)}

export const MISSILE_METAS: Readonly<Record<string, MissileMeta>> = {
  firebolt: FIREBOLT_META,
  fireball: FIREBALL_META,
  fireexplode: FIREEXPLODE_META,
}
`
  const metaTsPath = join(projectRoot, 'src', 'render', 'missiles-meta.ts')
  writeFileSync(metaTsPath, metaTsContent, 'utf-8')
  console.log(`[Missile Packer] Wrote ${metaTsPath}`)

  return metaRecord
}

// Execute standalone if called from CLI
if (process.argv[1]?.endsWith('pack-missiles.ts')) {
  bakeMissiles().catch((err: unknown) => {
    console.error('Bake missiles failed:', err)
    process.exit(1)
  })
}