// TDD: piece classification for textured rendering.
// renderPieces(snake, dir) -> array of texture names, one per segment (head first).
const assert = require('assert/strict')
const fs = require('fs')
const vm = require('vm')

const src = fs.readFileSync(__dirname + '/../src/common/snake.js', 'utf8')
const sandbox = { module: { exports: {} } }
vm.runInNewContext(src, sandbox)
const snake = sandbox.module.exports

// compass sides: e/w/n/s (screen coords, y grows downward)
function pieces(list, dir) { return snake.renderPieces(list, dir) }

// -- initial snake: head east, horizontal body, tail pointing west
assert.deepEqual(
  pieces([{ x: 6, y: 7 }, { x: 5, y: 7 }, { x: 4, y: 7 }], { x: 1, y: 0 }),
  ['head_e', 'body_h', 'tail_w'])

// -- vertical snake moving south
assert.deepEqual(
  pieces([{ x: 3, y: 5 }, { x: 3, y: 4 }, { x: 3, y: 4 + 1 }], { x: 0, y: 1 })
    .map((p, i) => i), // shape check below with explicit list instead
  [0, 1, 2])
assert.deepEqual(
  pieces([{ x: 3, y: 5 }, { x: 3, y: 6 }, { x: 3, y: 7 }], { x: 0, y: 1 }),
  ['head_s', 'body_v', 'tail_s'])

// -- corner: head turned from east to south
// snake [(6,8),(6,7),(5,7)]: neck connects south (to head) and west (to rest);
// tail cell (5,7)'s neighbor is east, so its tip points west
assert.deepEqual(
  pieces([{ x: 6, y: 8 }, { x: 6, y: 7 }, { x: 5, y: 7 }], { x: 0, y: 1 }),
  ['head_s', 'corner_sw', 'tail_w'])

// -- corner: head turned from east to north
assert.deepEqual(
  pieces([{ x: 6, y: 6 }, { x: 6, y: 7 }, { x: 5, y: 7 }], { x: 0, y: -1 }),
  ['head_n', 'corner_nw', 'tail_w'])

// -- corner heading west turning south (es corner mirrored)
// tail cell (5,7)'s neighbor is west, so its tip points east
assert.deepEqual(
  pieces([{ x: 4, y: 8 }, { x: 4, y: 7 }, { x: 5, y: 7 }], { x: -1, y: 0 }),
  ['head_w', 'corner_es', 'tail_e'])

// -- double corner (S shape): head moving south, west, then north —
// hand-verified: every middle cell of this tight zigzag is a corner
// [(6,8) head][ (6,7) sw ][ (5,7) en ][ (5,6) sw ][ (4,6) en ][ (4,5) tail ]
assert.deepEqual(
  pieces([{ x: 6, y: 8 }, { x: 6, y: 7 }, { x: 5, y: 7 }, { x: 5, y: 6 }, { x: 4, y: 6 }, { x: 4, y: 5 }], { x: 0, y: 1 }),
  ['head_s', 'corner_sw', 'corner_en', 'corner_sw', 'corner_en', 'tail_n'])

// -- every returned piece maps to a texture that must exist
const TEX = ['head_e', 'head_w', 'head_n', 'head_s',
  'body_h', 'body_v',
  'corner_en', 'corner_es', 'corner_nw', 'corner_sw',
  'tail_e', 'tail_w', 'tail_n', 'tail_s']
const dirTex = __dirname + '/../src/common/tex'
for (const p of TEX) {
  assert.ok(fs.existsSync(dirTex + '/' + p + '.png'), 'missing texture ' + p)
}

// -- food + board textures
assert.ok(fs.existsSync(dirTex + '/apple.png'), 'missing apple texture')
assert.ok(fs.existsSync(dirTex + '/board.png'), 'missing board texture')

console.log('PIECE CLASSIFICATION PASS')