import type { QrCode } from '../index'

export type PathItem = [ 'M', number, number ] | [ 'h', number ] | [ 'v', number ]
export type Path = PathItem[]
export type Paths = Path[]

/** Generate a set of vector paths for a QR code */
export function generatePaths(code: QrCode): Paths {
  const { matrix, size } = code

  const filled: boolean[][] = []

  for (let row = -1; row <= size; row++) {
    filled[row] = []
  }

  const path = []
  for (let row = 0; row < size; row++) {
    for (let col = 0; col < size; col++) {
      if (filled[row]![col]) continue

      filled[row]![col] = true

      if (isDark(row, col)) {
        if (!isDark(row - 1, col)) {
          path.push(plot(row, col, 'right'))
        }
      } else {
        if (isDark(row, col - 1)) {
          path.push(plot(row, col, 'down'))
        }
      }
    }
  }

  return path

  function isDark(row: number, col: number):boolean {
    if (row < 0 || col < 0 || row >= size || col >= size) return false
    return !! matrix[row]![col]
  }

  function plot(row0: number, col0: number, dir: 'right' | 'left' | 'down' | 'up'): Path {
    filled[row0]![col0] = true
    const res: Path = []

    res.push([ 'M', col0, row0 ])
    let row = row0
    let col = col0
    let len = 0

    do {
      switch (dir) {
        case 'right':
          filled[row]![col] = true
          if (isDark(row, col)) {
            filled[row - 1]![col] = true
            if (isDark(row - 1, col)) {
              res.push([ 'h', len ])
              len = 0
              dir = 'up'
            } else {
              len++
              col++
            }
          } else {
            res.push([ 'h', len ])
            len = 0
            dir = 'down'
          }
          break
        case 'left':
          filled[row - 1]![col - 1] = true
          if (isDark(row - 1, col - 1)) {
            filled[row]![col - 1] = true
            if (isDark(row, col - 1)) {
              res.push([ 'h', -len ])
              len = 0
              dir = 'down'
            } else {
              len++
              col--
            }
          } else {
            res.push([ 'h', -len ])
            len = 0
            dir = 'up'
          }
          break
        case 'down':
          filled[row]![col - 1] = true
          if (isDark(row, col - 1)) {
            filled[row]![col] = true
            if (isDark(row, col)) {
              res.push([ 'v', len ])
              len = 0
              dir = 'right'
            } else {
              len++
              row++
            }
          } else {
            res.push([ 'v', len ])
            len = 0
            dir = 'left'
          }
          break
        case 'up':
          filled[row - 1]![col] = true
          if (isDark(row - 1, col)) {
            filled[row - 1]![col - 1] = true
            if (isDark(row - 1, col - 1)) {
              res.push([ 'v', -len ])
              len = 0
              dir = 'left'
            } else {
              len++
              row--
            }
          } else {
            res.push([ 'v', -len ])
            len = 0
            dir = 'right'
          }
          break
      }
    } while (row != row0 || col != col0)

    return res
  }
}