// Copyright (c) 2020 Lars Pontoppidan. All rights reserved.
// Use of this source code is governed by the MIT license distributed with this software.
// Don't use this editor for any serious work.
// A lot of functionality is missing compared to your favourite editor :)
import strings
import os
import math
import term.ui as tui
import encoding.utf8
import encoding.utf8.east_asian

const rune_digits = [`0`, `1`, `2`, `3`, `4`, `5`, `6`, `7`, `8`, `9`]

const zero_width_unicode = [
    `\u034f`, // U+034F COMBINING GRAPHEME JOINER
    `\u061c`, // U+061C ARABIC LETTER MARK
    `\u17b4`, // U+17B4 KHMER VOWEL INHERENT AQ
    `\u17b5`, // U+17B5 KHMER VOWEL INHERENT AA
    `\u200a`, // U+200A HAIR SPACE
    `\u200b`, // U+200B ZERO WIDTH SPACE
    `\u200c`, // U+200C ZERO WIDTH NON-JOINER
    `\u200d`, // U+200D ZERO WIDTH JOINER
    `\u200e`, // U+200E LEFT-TO-RIGHT MARK
    `\u200f`, // U+200F RIGHT-TO-LEFT MARK
    `\u2060`, // U+2060 WORD JOINER
    `\u2061`, // U+2061 FUNCTION APPLICATION
    `\u2062`, // U+2062 INVISIBLE TIMES
    `\u2063`, // U+2063 INVISIBLE SEPARATOR
    `\u2064`, // U+2064 INVISIBLE PLUS
    `\u206a`, // U+206A INHIBIT SYMMETRIC SWAPPING
    `\u206b`, // U+206B ACTIVATE SYMMETRIC SWAPPING
    `\u206c`, // U+206C INHIBIT ARABIC FORM SHAPING
    `\u206d`, // U+206D ACTIVATE ARABIC FORM SHAPING
    `\u206e`, // U+206E NATIONAL DIGIT SHAPES
    `\u206f`, // U+206F NOMINAL DIGIT SHAPES
    `\ufeff`, // U+FEFF ZERO WIDTH NO-BREAK SPACE
]

enum Movement {
    up
    down
    left
    right
    home
    end
    page_up
    page_down
}

struct View {
pub:
    raw    string
    cursor Cursor
}

struct App {
mut:
    tui           &tui.Context = unsafe { nil }
    ed            &Buffer      = unsafe { nil }
    current_file  int
    files         []string
    status        string
    t             int
    magnet_x      int
    footer_height int = 2
    viewport      int
}

fn (mut a App) set_status(msg string, duration_ms int) {
    a.status = msg
    a.t = duration_ms
}

fn (mut a App) save() {
    if a.cfile().len > 0 {
        b := a.ed
        os.write_file(a.cfile(), b.raw()) or { panic(err) }
        a.set_status('Saved', 2000)
    } else {
        a.set_status('No file loaded', 4000)
    }
}

fn (mut a App) cfile() string {
    if a.files.len == 0 {
        return ''
    }
    if a.current_file >= a.files.len {
        return ''
    }
    return a.files[a.current_file]
}

fn (mut a App) visit_prev_file() {
    if a.files.len == 0 {
        a.current_file = 0
    } else {
        a.current_file = (a.current_file + a.files.len - 1) % a.files.len
    }
    a.init_file()
}

fn (mut a App) visit_next_file() {
    if a.files.len == 0 {
        a.current_file = 0
    } else {
        a.current_file = (a.current_file + a.files.len + 1) % a.files.len
    }
    a.init_file()
}

fn (mut a App) footer() {
    w, h := a.tui.window_width, a.tui.window_height
    mut b := a.ed
    // flat := b.flat()
    // snip := if flat.len > 19 { flat[..20] } else { flat }
    finfo := if a.cfile().len > 0 { ' (' + os.file_name(a.cfile()) + ')' } else { '' }
    mut status := a.status
    a.tui.draw_text(0, h - 1, '─'.repeat(w))
    footer := '${finfo} Line ${b.cursor.pos_y + 1:4}/${b.lines.len:-4}, Column ${b.cursor.pos_x + 1:3}/${b.cur_line().len:-3} index: ${b.cursor_index():5} (ESC = quit, Ctrl+s = save)'
    if footer.len < w {
        a.tui.draw_text((w - footer.len) / 2, h, footer)
    } else if footer.len == w {
        a.tui.draw_text(0, h, footer)
    } else {
        a.tui.draw_text(0, h, footer[..w])
    }
    if a.t <= 0 {
        status = ''
    } else {
        a.tui.set_bg_color(
            r: 200
            g: 200
            b: 200
        )
        a.tui.set_color(
            r: 0
            g: 0
            b: 0
        )
        a.tui.draw_text((w + 4 - status.len) / 2, h - 1, ' ${status} ')
        a.tui.reset()
        a.t -= 33
    }
}

struct Buffer {
    tab_width int = 4
pub mut:
    lines  []string
    cursor Cursor
}

fn (b Buffer) flat() string {
    return b.raw().replace_each(['\n', r'\n', '\t', r'\t'])
}

fn (b Buffer) raw() string {
    return b.lines.join('\n')
}

fn (b Buffer) view(from int, to int) View {
    l := b.cur_line().runes()
    mut x := 0
    for i := 0; i < b.cursor.pos_x && i < l.len; i++ {
        if l[i] == `\t` {
            x += b.tab_width
            continue
        }
        x++
    }
    mut lines := []string{}
    for i, line in b.lines {
        if i >= from && i <= to {
            lines << line
        }
    }
    raw := lines.join('\n')
    return View{
        raw:    raw.replace('\t', strings.repeat(` `, b.tab_width))
        cursor: Cursor{
            pos_x: x
            pos_y: b.cursor.pos_y
        }
    }
}

fn (b Buffer) line(i int) string {
    if i < 0 || i >= b.lines.len {
        return ''
    }
    return b.lines[i]
}

fn (b Buffer) cur_line() string {
    return b.line(b.cursor.pos_y)
}

fn (b Buffer) cur_slice() string {
    line := b.line(b.cursor.pos_y).runes()
    if b.cursor.pos_x == 0 || b.cursor.pos_x > line.len {
        return ''
    }
    return line[..b.cursor.pos_x].string()
}

fn (b Buffer) cursor_index() int {
    mut i := 0
    for y, line in b.lines {
        if b.cursor.pos_y == y {
            i += b.cursor.pos_x
            break
        }
        i += line.runes().len + 1
    }
    return i
}

fn (mut b Buffer) put(s string) {
    has_line_ending := s.contains('\n')
    x, y := b.cursor.xy()
    if b.lines.len == 0 {
        b.lines.prepend('')
    }
    line := b.lines[y].runes()
    l, r := line[..x].string(), line[x..].string()
    if has_line_ending {
        mut lines := s.split('\n')
        lines[0] = l + lines[0]
        lines[lines.len - 1] += r
        b.lines.delete(y)
        b.lines.insert(y, lines)
        last := lines[lines.len - 1].runes()
        b.cursor.set(last.len, y + lines.len - 1)
        if s == '\n' {
            b.cursor.set(0, b.cursor.pos_y)
        }
    } else {
        b.lines[y] = l + s + r
        b.cursor.set(x + s.runes().len, y)
    }
    $if debug {
        flat := s.replace('\n', r'\n')
        eprintln(@MOD + '.' + @STRUCT + '::' + @FN + ' "${flat}"')
    }
}

fn (mut b Buffer) del(amount int) string {
    if amount == 0 {
        return ''
    }
    x, y := b.cursor.xy()
    if amount < 0 { // don't delete left if we're at 0,0
        if x == 0 && y == 0 {
            return ''
        }
    } else if x >= b.cur_line().runes().len && y >= b.lines.len - 1 {
        return ''
    }
    mut removed := ''
    if amount < 0 { // backspace (backward)
        i := b.cursor_index()
        raw_runes := b.raw().runes()
        removed = raw_runes[i + amount..i].string()
        mut left := amount * -1
        for li := y; li >= 0 && left > 0; li-- {
            ln := b.lines[li].runes()
            if left == ln.len + 1 { // All of the line + 1 - since we're going backwards the "+1" is the line break delimiter.
                b.lines.delete(li)
                left = 0
                if y == 0 {
                    return ''
                }
                line_above := b.lines[li - 1].runes()
                b.cursor.pos_x = line_above.len
                b.cursor.pos_y--
                break
            } else if left > ln.len {
                b.lines.delete(li)
                if ln.len == 0 { // line break delimiter
                    left--
                    if y == 0 {
                        return ''
                    }
                    line_above := b.lines[li - 1].runes()
                    b.cursor.pos_x = line_above.len
                } else {
                    left -= ln.len
                }
                b.cursor.pos_y--
            } else {
                if x == 0 {
                    if y == 0 {
                        return ''
                    }
                    line_above := b.lines[li - 1].runes()
                    if ln.len == 0 { // at line break
                        b.lines.delete(li)
                        b.cursor.pos_y--
                        b.cursor.pos_x = line_above.len
                    } else {
                        b.lines[li - 1] = line_above.string() + ln.string()
                        b.lines.delete(li)
                        b.cursor.pos_y--
                        b.cursor.pos_x = line_above.len
                    }
                } else if x == 1 {
                    runes := b.lines[li].runes()
                    b.lines[li] = runes[left..].string()
                    b.cursor.pos_x = 0
                } else {
                    b.lines[li] = ln[..x - left].string() + ln[x..].string()
                    b.cursor.pos_x -= left
                }
                left = 0
                break
            }
        }
    } else { // delete (forward)
        i := b.cursor_index() + 1
        raw_buffer := b.raw().runes()
        from_i := i
        mut to_i := i + amount

        if to_i > raw_buffer.len {
            to_i = raw_buffer.len
        }
        removed = raw_buffer[from_i..to_i].string()
        mut left := amount
        for li := y; li >= 0 && left > 0; li++ {
            ln := b.lines[li].runes()
            if x == ln.len { // at line end
                if y + 1 <= b.lines.len {
                    b.lines[li] = ln.string() + b.lines[y + 1]
                    b.lines.delete(y + 1)
                    left--
                    b.del(left)
                }
            } else if left > ln.len {
                b.lines.delete(li)
                left -= ln.len
            } else {
                b.lines[li] = ln[..x].string() + ln[x + left..].string()
                left = 0
            }
        }
    }
    $if debug {
        flat := removed.replace('\n', r'\n')
        eprintln(@MOD + '.' + @STRUCT + '::' + @FN + ' "${flat}"')
    }
    return removed
}

fn (mut b Buffer) free() {
    $if debug {
        eprintln(@MOD + '.' + @STRUCT + '::' + @FN)
    }
    for line in b.lines {
        unsafe { line.free() }
    }
    unsafe { b.lines.free() }
}

fn (mut b Buffer) move_updown(amount int) {
    b.cursor.move(0, amount)
    // Check the move
    line := b.cur_line().runes()
    if b.cursor.pos_x > line.len {
        b.cursor.set(line.len, b.cursor.pos_y)
    }
}

// move_cursor will navigate the cursor within the buffer bounds
fn (mut b Buffer) move_cursor(amount int, movement Movement) {
    cur_line := b.cur_line().runes()
    match movement {
        .up {
            if b.cursor.pos_y - amount >= 0 {
                b.move_updown(-amount)
            }
        }
        .down {
            if b.cursor.pos_y + amount < b.lines.len {
                b.move_updown(amount)
            }
        }
        .page_up {
            dlines := math.min(b.cursor.pos_y, amount)
            b.move_updown(-dlines)
        }
        .page_down {
            dlines := math.min(b.lines.len - 1, b.cursor.pos_y + amount) - b.cursor.pos_y
            b.move_updown(dlines)
        }
        .left {
            if b.cursor.pos_x - amount >= 0 {
                b.cursor.move(-amount, 0)
            } else if b.cursor.pos_y > 0 {
                b.cursor.set(b.line(b.cursor.pos_y - 1).runes().len, b.cursor.pos_y - 1)
            }
        }
        .right {
            if b.cursor.pos_x + amount <= cur_line.len {
                b.cursor.move(amount, 0)
            } else if b.cursor.pos_y + 1 < b.lines.len {
                b.cursor.set(0, b.cursor.pos_y + 1)
            }
        }
        .home {
            b.cursor.set(0, b.cursor.pos_y)
        }
        .end {
            b.cursor.set(cur_line.len, b.cursor.pos_y)
        }
    }
}

fn (mut b Buffer) move_to_word(movement Movement) {
    a := if movement == .left { -1 } else { 1 }

    mut line := b.cur_line().runes()
    mut x, mut y := b.cursor.pos_x, b.cursor.pos_y
    if x + a < 0 && y > 0 {
        y--
        line = b.line(b.cursor.pos_y - 1).runes()
        x = line.len
    } else if x + a >= line.len && y + 1 < b.lines.len {
        y++
        line = b.line(b.cursor.pos_y + 1).runes()
        x = 0
    }
    // first, move past all non-`a-zA-Z0-9_` characters
    for x + a >= 0 && x + a < line.len && !(utf8.is_letter(line[x + a])
        || line[x + a] in rune_digits || line[x + a] == `_`) {
        x += a
    }
    // then, move past all the letters and numbers
    for x + a >= 0 && x + a < line.len && (utf8.is_letter(line[x + a])
        || line[x + a] in rune_digits || line[x + a] == `_`) {
        x += a
    }
    // if the cursor is out of bounds, move it to the next/previous line
    if x + a >= 0 && x + a <= line.len {
        x += a
    } else if a < 0 && y + 1 > b.lines.len && y - 1 >= 0 {
        y += a
        x = 0
    }
    b.cursor.set(x, y)
}

struct Cursor {
pub mut:
    pos_x int
    pos_y int
}

fn (mut c Cursor) set(x int, y int) {
    c.pos_x = x
    c.pos_y = y
}

fn (mut c Cursor) move(x int, y int) {
    c.pos_x += x
    c.pos_y += y
}

fn (c Cursor) xy() (int, int) {
    return c.pos_x, c.pos_y
}

// App callbacks
fn init(mut app App) {
    app.init_file()
}

fn (mut a App) init_file() {
    a.ed = &Buffer{}
    mut init_y := 0
    mut init_x := 0
    if a.files.len > 0 && a.current_file < a.files.len && a.files[a.current_file].len > 0 {
        if !os.is_file(a.files[a.current_file]) && a.files[a.current_file].contains(':') {
            // support the file:line:col: format
            fparts := a.files[a.current_file].split(':')
            if fparts.len > 0 {
                a.files[a.current_file] = fparts[0]
            }
            if fparts.len > 1 {
                init_y = fparts[1].int() - 1
            }
            if fparts.len > 2 {
                init_x = fparts[2].int() - 1
            }
        }
        if os.is_file(a.files[a.current_file]) {
            // 'vico: ' +
            a.tui.set_window_title(a.files[a.current_file])
            mut b := a.ed
            content := os.read_file(a.files[a.current_file]) or { panic(err) }
            b.put(content)
            a.ed.cursor.pos_x = init_x
            a.ed.cursor.pos_y = init_y
        }
    }
}

fn (a &App) view_height() int {
    return a.tui.window_height - a.footer_height - 1
}

// magnet_cursor_x will place the cursor as close to it's last move left or right as possible
fn (mut a App) magnet_cursor_x() {
    mut buffer := a.ed
    if buffer.cursor.pos_x < a.magnet_x {
        if a.magnet_x < buffer.cur_line().runes().len {
            move_x := a.magnet_x - buffer.cursor.pos_x
            buffer.move_cursor(move_x, .right)
        }
    }
}

fn frame(mut a App) {
    mut ed := a.ed
    a.tui.clear()
    scroll_limit := a.view_height()
    // scroll down
    if ed.cursor.pos_y > a.viewport + scroll_limit { // scroll down
        a.viewport = ed.cursor.pos_y - scroll_limit
    } else if ed.cursor.pos_y < a.viewport { // scroll up
        a.viewport = ed.cursor.pos_y
    }
    view := ed.view(a.viewport, scroll_limit + a.viewport)
    a.tui.draw_text(0, 0, view.raw)
    a.footer()

    // Unicode: Handle correct mapping of cursor X position in terminal.
    mut ch_x := view.cursor.pos_x
    mut sl := ed.cur_slice().replace('\t', ' '.repeat(ed.tab_width))
    if sl.len > 0 {
        // Strip out any zero-width codepoints.
        sl = sl.runes().filter(it !in zero_width_unicode).string()
        ch_x = east_asian.display_width(sl, 1)
    }

    a.tui.set_cursor_position(ch_x + 1, ed.cursor.pos_y + 1 - a.viewport)
    a.tui.flush()
}

fn event(e &tui.Event, mut a App) {
    mut buffer := a.ed
    if e.typ == .key_down {
        match e.code {
            .escape {
                exit(0)
            }
            .enter {
                buffer.put('\n')
            }
            .backspace {
                buffer.del(-1)
            }
            .delete {
                buffer.del(1)
            }
            .left {
                if e.modifiers == .ctrl {
                    buffer.move_to_word(.left)
                } else if e.modifiers.is_empty() {
                    buffer.move_cursor(1, .left)
                }
                a.magnet_x = buffer.cursor.pos_x
            }
            .right {
                if e.modifiers == .ctrl {
                    buffer.move_to_word(.right)
                } else if e.modifiers.is_empty() {
                    buffer.move_cursor(1, .right)
                }
                a.magnet_x = buffer.cursor.pos_x
            }
            .up {
                buffer.move_cursor(1, .up)
                a.magnet_cursor_x()
            }
            .down {
                buffer.move_cursor(1, .down)
                a.magnet_cursor_x()
            }
            .page_up {
                buffer.move_cursor(a.view_height(), .page_up)
            }
            .page_down {
                buffer.move_cursor(a.view_height(), .page_down)
            }
            .home {
                buffer.move_cursor(1, .home)
            }
            .end {
                buffer.move_cursor(1, .end)
            }
            48...57, 97...122 { // 0-9a-zA-Z
                if e.modifiers == .ctrl {
                    if e.code == .s {
                        a.save()
                    }
                } else if !(e.modifiers.has(.ctrl | .alt) || e.code == .null) {
                    buffer.put(e.ascii.ascii_str())
                }
            }
            else {
                if e.modifiers == .alt {
                    if e.code == .comma {
                        a.visit_prev_file()
                        return
                    }
                    if e.code == .period {
                        a.visit_next_file()
                        return
                    }
                }

                buffer.put(e.utf8)
            }
        }
    } else if e.typ == .mouse_scroll {
        direction := if e.direction == .up { Movement.down } else { Movement.up }
        buffer.move_cursor(1, direction)
    }
}

type InitFn = fn (voidptr)

type EventFn = fn (&tui.Event, voidptr)

type FrameFn = fn (voidptr)

fn main() {
    mut files := []string{}
    if os.args.len > 1 {
        files << os.args[1..]
    }
    mut a := &App{
        files: files
    }
    a.tui = tui.init(
        user_data:      a
        init_fn:        InitFn(init)
        frame_fn:       FrameFn(frame)
        event_fn:       EventFn(event)
        capture_events: true
    )
    a.tui.run()!
}