fn diag_clamp_offset(bytes: Span<u8>, offset: usize) -> usize {
    if offset > std.mem.len(bytes) {
        return std.mem.len(bytes)
    }
    return offset
}

fn diag_line_start(bytes: Span<u8>, offset: usize) -> usize {
    let cursor: usize = diag_clamp_offset(bytes, offset)
    var start: usize = cursor
    while start > 0 && bytes[start - 1] != 10_u8 {
        start = start - 1
    }
    return start
}

fn diag_line_end(bytes: Span<u8>, offset: usize) -> usize {
    var end: usize = diag_clamp_offset(bytes, offset)
    while end < std.mem.len(bytes) && bytes[end] != 10_u8 {
        end = end + 1
    }
    if end > 0 && bytes[end - 1] == 13_u8 {
        return end - 1
    }
    return end
}

fn diag_line(bytes: Span<u8>, offset: usize) -> usize {
    let cursor: usize = diag_clamp_offset(bytes, offset)
    var line: usize = 1
    var index: usize = 0
    while index < cursor {
        if bytes[index] == 10_u8 {
            line = line + 1
        }
        index = index + 1
    }
    return line
}

fn diag_column(bytes: Span<u8>, offset: usize) -> usize {
    let cursor: usize = diag_clamp_offset(bytes, offset)
    let start: usize = diag_line_start(bytes, cursor)
    return (cursor - start) + 1
}

fn diag_line_text(bytes: Span<u8>, offset: usize) -> Span<u8> {
    let start: usize = diag_line_start(bytes, offset)
    let end: usize = diag_line_end(bytes, offset)
    return bytes[start..end]
}

fn diag_range_len(bytes: Span<u8>, start: usize, end: usize) -> usize {
    let first: usize = diag_clamp_offset(bytes, start)
    let last: usize = diag_clamp_offset(bytes, end)
    if last < first {
        return 0
    }
    return last - first
}

fn diag_range_text(bytes: Span<u8>, start: usize, end: usize) -> Span<u8> {
    let first: usize = diag_clamp_offset(bytes, start)
    let last: usize = diag_clamp_offset(bytes, end)
    if last < first {
        return bytes[first..first]
    }
    return bytes[first..last]
}

fn diag_write_span(buffer: MutSpan<u8>, offset: usize, bytes: Span<u8>) -> Maybe<usize> {
    if offset > std.mem.len(buffer) {
        return null
    }
    if std.mem.len(bytes) > std.mem.len(buffer) - offset {
        return null
    }
    var index: usize = 0
    while index < std.mem.len(bytes) {
        buffer[offset + index] = bytes[index]
        index = index + 1
    }
    return offset + std.mem.len(bytes)
}

fn diag_write_usize(buffer: MutSpan<u8>, offset: usize, value: usize) -> Maybe<usize> {
    if offset > std.mem.len(buffer) {
        return null
    }
    var digits: usize = 1
    var scan: usize = value
    while scan >= 10 {
        digits = digits + 1
        scan = scan / 10
    }
    if offset + digits > std.mem.len(buffer) {
        return null
    }
    var cursor: usize = offset + digits
    var current: usize = value
    while cursor > offset {
        cursor = cursor - 1
        let digit: u8 = (current % 10) as u8
        buffer[cursor] = 48_u8 + digit
        current = current / 10
    }
    return offset + digits
}

fn diag_format_location(buffer: MutSpan<u8>, path: Span<u8>, line: usize, column: usize) -> Maybe<Span<u8>> {
    var offset: usize = 0
    let wrote_path: Maybe<usize> = diag_write_span(buffer, offset, path)
    if !wrote_path.has {
        return null
    }
    offset = wrote_path.value
    let first_colon: Maybe<usize> = diag_write_span(buffer, offset, ":")
    if !first_colon.has {
        return null
    }
    offset = first_colon.value
    let wrote_line: Maybe<usize> = diag_write_usize(buffer, offset, line)
    if !wrote_line.has {
        return null
    }
    offset = wrote_line.value
    let second_colon: Maybe<usize> = diag_write_span(buffer, offset, ":")
    if !second_colon.has {
        return null
    }
    offset = second_colon.value
    let wrote_column: Maybe<usize> = diag_write_usize(buffer, offset, column)
    if wrote_column.has {
        return buffer[..wrote_column.value]
    }
    return null
}

fn diag_format_offset_location(buffer: MutSpan<u8>, path: Span<u8>, bytes: Span<u8>, offset: usize) -> Maybe<Span<u8>> {
    return diag_format_location(buffer, path, diag_line(bytes, offset), diag_column(bytes, offset))
}