package jsonc

// ToJSON strips out comments and trailing commas and convert the input to a
// valid JSON per the official spec: https://tools.ietf.org/html/rfc8259
//
// The resulting JSON will always be the same length as the input and it will
// include all of the same line breaks at matching offsets. This is to ensure
// the result can be later processed by a external parser and that that
// parser will report messages or errors with the correct offsets.
func ToJSON(src []byte) []byte {
	return toJSON(src, nil)
}

// ToJSONInPlace is the same as ToJSON, but this method reuses the input json
// buffer to avoid allocations. Do not use the original bytes slice upon return.
func ToJSONInPlace(src []byte) []byte {
	return toJSON(src, src)
}

func toJSON(src, dst []byte) []byte {
	dst = dst[:0]
	for i := 0; i < len(src); i++ {
		if src[i] == '/' {
			if i < len(src)-1 {
				if src[i+1] == '/' {
					dst = append(dst, ' ', ' ')
					i += 2
					for ; i < len(src); i++ {
						if src[i] == '\n' {
							dst = append(dst, '\n')
							break
						} else if src[i] == '\t' || src[i] == '\r' {
							dst = append(dst, src[i])
						} else {
							dst = append(dst, ' ')
						}
					}
					continue
				}
				if src[i+1] == '*' {
					dst = append(dst, ' ', ' ')
					j := i
					i += 2
					for ; i < len(src)-1; i++ {
						if src[i] == '*' && src[i+1] == '/' {
							dst = append(dst, ' ', ' ')
							i++
							j = -1
							break
						} else if src[i] == '\n' || src[i] == '\t' ||
							src[i] == '\r' {
							dst = append(dst, src[i])
						} else {
							dst = append(dst, ' ')
						}
					}
					if j != -1 {
						dst = append(dst, ' ')
						dst[j] = '/'
						dst[j+1] = '*'
					}
					continue
				}
			}
		}
		dst = append(dst, src[i])
		if src[i] == '"' {
			for i = i + 1; i < len(src); i++ {
				dst = append(dst, src[i])
				if src[i] == '"' {
					j := i - 1
					for ; ; j-- {
						if src[j] != '\\' {
							break
						}
					}
					if (j-i)%2 != 0 {
						break
					}
				}
			}
		} else if src[i] == '}' || src[i] == ']' {
			for j := len(dst) - 2; j >= 0; j-- {
				if dst[j] <= ' ' {
					continue
				}
				if dst[j] == ',' {
					dst[j] = ' '
				}
				break
			}
		}
	}
	return dst
}