module token

// Pos represents pos data used by token.
pub struct Pos {
pub:
    offset int
    id     int
}

// str returns the string form for Pos.
pub fn (p Pos) str() string {
    return '{ offset: ${p.offset}, id: ${p.id} }'
}

// is_valid reports whether is valid applies in token.
pub fn (p Pos) is_valid() bool {
    return p.id > 0
}

// Position represents position data used by token.
pub struct Position {
pub:
    filename string
    offset   int
    line     int
    column   int
}

// str returns the string form for Position.
pub fn (p Position) str() string {
    return '${p.filename}:${p.line}:${p.column}'
}

// File represents file data used by token.
pub struct File {
pub:
    name string
    base int
    size int
mut:
    line_offsets []int = [0]
    id_counter   &int  = unsafe { nil }
}

// FileSet represents file set data used by token.
pub struct FileSet {
mut:
    base       int = 1
    id_counter int
    files      []&File
}

// new creates a FileSet value for token.
pub fn FileSet.new() &FileSet {
    return &FileSet{}
}

// add_file updates add file state for FileSet.
pub fn (mut fs FileSet) add_file(filename string, base_ int, size int) &File {
    mut base := if base_ < 0 { fs.base } else { base_ }
    if base < fs.base {
        panic('invalid base ${base} (should be >= ${fs.base}')
    }
    file := &File{
        name:       filename
        base:       base
        size:       size
        id_counter: &fs.id_counter
    }
    if size < 0 {
        panic('invalid size ${size} (should be >= 0)')
    }
    base += size + 1
    if base < 0 {
        panic('token.Pos offset overflow (> 2G of source code in file set)')
    }
    fs.base = base
    fs.files << file
    return file
}

// search_files supports search files handling for token.
fn search_files(files []&File, x int) int {
    mut min, mut max := 0, files.len
    for min < max {
        mid := (min + max) / 2
        if files[mid].base <= x {
            min = mid + 1
        } else {
            max = mid
        }
    }
    return min - 1
}

// file supports file handling for FileSet.
pub fn (mut fs FileSet) file(pos Pos) &File {
    i := search_files(fs.files, pos.offset)
    if i >= 0 {
        file := fs.files[i]
        if pos.offset <= file.base + file.size {
            return file
        }
    }
    dump(fs)
    panic('cannot find file for pos: ${pos}')
}

// add_line updates add line state for File.
@[inline]
pub fn (mut f File) add_line(offset int) {
    f.line_offsets << offset
}

// line_count supports line count handling for File.
@[inline]
pub fn (f &File) line_count() int {
    return f.line_offsets.len
}

// line_start supports line start handling for File.
pub fn (f &File) line_start(line int) int {
    idx := line - 1
    if idx < 0 || idx >= f.line_offsets.len {
        panic('invalid line `${line}` (must be > 0 & < ${f.line_count()})')
    }
    return f.line_offsets[idx]
}

// line supports line handling for File.
pub fn (f &File) line(pos Pos) int {
    return f.find_line(pos.offset - f.base)
}

// pos supports pos handling for File.
pub fn (mut f File) pos(offset int) Pos {
    if offset > f.size {
        panic('invalid offset')
    }
    mut current_id := 0
    mut next_id := 0
    unsafe {
        current_id = *f.id_counter
    }
    next_id = current_id + 1
    unsafe {
        *f.id_counter = next_id
    }
    return Pos{
        offset: f.base + offset
        id:     next_id
    }
}

// position supports position handling for File.
pub fn (f &File) position(pos Pos) Position {
    offset := pos.offset - f.base
    line, column := f.find_line_and_column(offset)
    return Position{
        filename: f.name
        offset:   offset
        line:     line
        column:   column
    }
}

// find_line_and_column resolves find line and column information for token.
pub fn (f &File) find_line_and_column(pos int) (int, int) {
    line := f.find_line(pos)
    return line, pos - f.line_offsets[line - 1] + 1
}

// find_line resolves find line information for token.
pub fn (f &File) find_line(pos int) int {
    mut min, mut max := 0, f.line_offsets.len
    for min < max {
        mid := (min + max) / 2
        if f.line_offsets[mid] <= pos {
            min = mid + 1
        } else {
            max = mid
        }
    }
    return min
}