/**
 * tabBar 图标生成脚本（零依赖：内置 zlib + 手写最小 PNG 编码器）
 *
 * 生成 81x81 RGBA 透明底线性图标到 src/static/tabbar/：
 *   - workbench（四宫格）/ bills（单据）/ profile（人像）
 *   - 普通态 #909399，选中态 #2979FF（与 pages.json tabBar 配色一致）
 *
 * 用法：npm run icons:gen
 */
import { deflateSync } from 'node:zlib'
import { mkdirSync, writeFileSync } from 'node:fs'
import { dirname, resolve } from 'node:path'
import { fileURLToPath } from 'node:url'

const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '..')
const OUT_DIR = resolve(ROOT, 'src/static/tabbar')
const SIZE = 81 // 微信推荐 tabBar 图标尺寸
const SAMPLES = 4 // 每像素 4x4 超采样抗锯齿

const COLOR_NORMAL = [0x90, 0x93, 0x99]
const COLOR_ACTIVE = [0x29, 0x79, 0xff]

// ---------- 最小 PNG 编码器 ----------

let CRC_TABLE = null
function crc32(buf) {
  if (!CRC_TABLE) {
    CRC_TABLE = new Uint32Array(256)
    for (let n = 0; n < 256; n++) {
      let c = n
      for (let k = 0; k < 8; k++) {
        c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1
      }
      CRC_TABLE[n] = c >>> 0
    }
  }
  let c = 0xffffffff
  for (let i = 0; i < buf.length; i++) {
    c = CRC_TABLE[(c ^ buf[i]) & 0xff] ^ (c >>> 8)
  }
  return (c ^ 0xffffffff) >>> 0
}

function chunk(type, data) {
  const len = Buffer.alloc(4)
  len.writeUInt32BE(data.length)
  const typeBuf = Buffer.from(type, 'ascii')
  const crc = Buffer.alloc(4)
  crc.writeUInt32BE(crc32(Buffer.concat([typeBuf, data])))
  return Buffer.concat([len, typeBuf, data, crc])
}

function encodePng(width, height, rgba) {
  const sig = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
  const ihdr = Buffer.alloc(13)
  ihdr.writeUInt32BE(width, 0)
  ihdr.writeUInt32BE(height, 4)
  ihdr[8] = 8 // 位深
  ihdr[9] = 6 // RGBA
  const stride = width * 4
  const raw = Buffer.alloc(height * (stride + 1))
  for (let y = 0; y < height; y++) {
    raw[y * (stride + 1)] = 0 // 每行 filter 0
    rgba.copy(raw, y * (stride + 1) + 1, y * stride, (y + 1) * stride)
  }
  const idat = deflateSync(raw, { level: 9 })
  return Buffer.concat([sig, chunk('IHDR', ihdr), chunk('IDAT', idat), chunk('IEND', Buffer.alloc(0))])
}

// ---------- 形状 SDF（返回像素点是否落在描边内） ----------

/** 圆角矩形描边 |sdf| <= w/2 */
function roundRect(px, py, cx, cy, hw, hh, r, w) {
  const qx = Math.abs(px - cx) - (hw - r)
  const qy = Math.abs(py - cy) - (hh - r)
  const d =
    Math.hypot(Math.max(qx, 0), Math.max(qy, 0)) + Math.min(Math.max(qx, qy), 0) - r
  return Math.abs(d) <= w / 2
}

/** 圆形描边 */
function circle(px, py, cx, cy, r, w) {
  return Math.abs(Math.hypot(px - cx, py - cy) - r) <= w / 2
}

/** 水平胶囊线段（横线） */
function hCapsule(px, py, x1, x2, y, r) {
  const cx = Math.min(Math.max(px, x1), x2)
  return Math.hypot(px - cx, py - y) <= r
}

// ---------- 三个图标（inside(x, y) → boolean） ----------

/** 工作台：四宫格（4 个圆角方框） */
function iconWorkbench(x, y) {
  const cells = [
    [24, 24],
    [57, 24],
    [24, 57],
    [57, 57]
  ]
  return cells.some(([cx, cy]) => roundRect(x, y, cx, cy, 14, 14, 5, 5))
}

/** 单据：圆角矩形外框 + 三条横线 */
function iconBills(x, y) {
  if (roundRect(x, y, 40.5, 40.5, 22, 30, 7, 5)) return true
  return [29, 41, 53].some((ly) => hCapsule(x, y, 30, 51, ly, 2.5))
}

/** 我的：圆头 + 肩弧 */
function iconProfile(x, y) {
  if (circle(x, y, 40.5, 26, 12, 5)) return true
  // 肩弧：大圆描边裁剪出顶部弧段
  return y <= 62 && circle(x, y, 40.5, 78, 26, 5)
}

// ---------- 渲染与输出 ----------

function render(inside, [r, g, b]) {
  const rgba = Buffer.alloc(SIZE * SIZE * 4)
  const step = 1 / SAMPLES
  for (let y = 0; y < SIZE; y++) {
    for (let x = 0; x < SIZE; x++) {
      let hit = 0
      for (let sy = 0; sy < SAMPLES; sy++) {
        for (let sx = 0; sx < SAMPLES; sx++) {
          if (inside(x + (sx + 0.5) * step, y + (sy + 0.5) * step)) hit++
        }
      }
      const alpha = Math.round((hit / (SAMPLES * SAMPLES)) * 255)
      const idx = (y * SIZE + x) * 4
      rgba[idx] = r
      rgba[idx + 1] = g
      rgba[idx + 2] = b
      rgba[idx + 3] = alpha
    }
  }
  return encodePng(SIZE, SIZE, rgba)
}

const icons = [
  { name: 'workbench', draw: iconWorkbench },
  { name: 'bills', draw: iconBills },
  { name: 'profile', draw: iconProfile }
]

mkdirSync(OUT_DIR, { recursive: true })
for (const { name, draw } of icons) {
  const normal = resolve(OUT_DIR, `${name}.png`)
  const active = resolve(OUT_DIR, `${name}-active.png`)
  writeFileSync(normal, render(draw, COLOR_NORMAL))
  writeFileSync(active, render(draw, COLOR_ACTIVE))
  console.log(`[icons] ${name}.png / ${name}-active.png 已生成`)
}
console.log(`[icons] 输出目录: ${OUT_DIR}`)