#if OS == .WINDOWS {
    #load "windows.jai";
} else #if (OS == .LINUX) || (OS == .MACOS) {
    #load "unix.jai";
} else {
    #assert(false, "Unsupported OS.");
}

#import "Basic";
#import "String";
#import "Thread";

Drawings :: struct {
    // TODO Maybe just use unicode instead of jumping back and forth between drawing mode?!
    // test_drawing_without_mode :: () {
    // top := "┌───┐";
    // btm := "└───┘";
    // print(">%<\n", top);
    // print(">%<\n", btm);
    // }
    // #run test_drawing_without_mode();
    CornerBR                :: "\x6A";
    CornerTR                :: "\x6B";
    CornerTL                :: "\x6C";
    CornerBL                :: "\x6D";
    Cross                   :: "\x6E";
    LineH                   :: "\x71";
    TeeL                    :: "\x74";
    TeeR                    :: "\x75";
    TeeB                    :: "\x76";
    TeeT                    :: "\x77";
    LineV                   :: "\x78";

    Blank                   :: "\x5F";
    Diamond                 :: "\x60";
    Checkerboard            :: "\x61";
    PlusMinus               :: "\x67";
    LessThanOrEqual         :: "\x79";
    GreaterThanOrEqual      :: "\x7A";
    Pi                      :: "\x7B";
    NotEqual                :: "\x7C";
    CenteredDot             :: "\x7E";
}

Commands :: struct {
    AlternateScreenBuffer   :: "\e[?1049h";
    MainScreenBuffer          :: "\e[?1049l";

    DrawingMode             :: "\e(0";
    TextMode                :: "\e(B";
    ClearScreen             :: "\e[2J";
    ClearLine               :: "\e[2K";

    Bell                    :: "\x07";

    SetWindowTitle          :: "\e]0;%\x07";

    RefreshWindow           :: "\e[7t"; // TODO Not yet tested.

    SetUTF8                 :: "\e%G"; // TODO TEST ME PLEASE

    // WIP WIP WIP
    // Add commands to change StyleNormal/Italic/Bold/Color/WhatNot!
    

    // Cursor Position
    SetCursorPosition       :: "\e[%;%H";

    // Cursor Visibility
    ShowCursor              :: "\e[?25h";
    HideCursor              :: "\e[?25l";
    StartBlinking           :: "\e[?25h]";
    StopBlinking            :: "\e[?25l]";
    SaveCursorPosition      :: "\e7";
    RestoreCursorPosition   :: "\e8";

    // Cursor Shape
    DefaultShape            :: "\e[0 q";
    BlinkingBlockShape      :: "\e[1 q";
    SteadyBlockShape        :: "\e[2 q";
    BlinkingUnderlineShape  :: "\e[3 q";
    SteadyUnderlineShape    :: "\e[4 q";
    BlinkingBarShape        :: "\e[5 q";
    SteadyBarShape          :: "\e[6 q";

    // Input Mode
    KeypadAppMode           :: "\e=";
    KeypadNumMode           :: "\e>";
    CursorAppMode           :: "\e[?1h";
    CursorNormalMode        :: "\e[?1l";

    // Query State
    QueryCursorPosition     :: "\e[6n"; // Emits the cursor position as: "ESC [ <r> ; <c> R" Where <r> = row and <c> = column.
    QueryDeviceAttributes   :: "\e[0c";
    QueryWindowSizeInChars  :: "\e[18t"; // Emits the window size as: "ESC [ 8 <r> ; <c> t" Where <r> = row and <c> = column. TODO Does not work on windows.
    
}

GraphicsStyle :: struct {
    BackgroundColor : u8;
    ForegroundColor : u8;
    Bold            : bool;
    Italic          : bool;
    Underline       : bool;
    Blinking        : bool;
    Inverse         : bool;
    StrikeThrough   : bool;
}

// TODO Maybe make the OS_* procedures as inline?!

/*
    We wanted the Key type to represent either UTF-8 encoded characters and also keyboard keys.
    The UTF-8 only requires up to 4 bytes, but some keyboard keys return up to 6 bytes.
    Therefore, we rounded it up to 8 bytes to support all this and more (if needed).
    
    This has to be compatible with: (#char "a" == key) ... so "a" must be stored in the LSB of key
            |-|-|-|-|-|
    string  |a|b|c|0|0|
    key/u64 |0|0|c|b|a| -> that in memory lays as (BE:|0|0|c|b|a|) and (LE:|a|b|c|0|0|)
*/

Key :: u64;

KEY_SIZE :: #run type_info(Key).runtime_size;

Keys :: struct {
    // Terminal key-codes have 1 to 6 bytes, so we can signal special cases setting the edge-bytes.
    None    : Key : 0xF0000000_0000000F;
    Resize  : Key : 0xF0000000_0000001F;

    Up      : Key : #run to_key("\e[A");
    Down    : Key : #run to_key("\e[B");
    Right   : Key : #run to_key("\e[C");
    Left    : Key : #run to_key("\e[D");

    PgUp    : Key : #run to_key("\e[5~");
    PgDown  : Key : #run to_key("\e[6~");
}

to_key :: inline (str: $T) -> Key #modify { return T == ([]u8) || T == string; } {
    k: Key;
    // #if DEBUG {
    // assert(str.count <= 8); // TODO Add DEBUG to module parameters.
    // }
    for 0..str.count-1 #no_abc {
        k |= ((cast(u64)str[it]) << (it*8));
    }
    return k;
}

to_string :: inline (key: Key) -> string {
    str := talloc_string(KEY_SIZE);
    str.count = 0;
    while key != 0 #no_abc {
        str[str.count] = xx key & 0xFF;
        key >>= 8;
        str.count += 1;
    }
	return str;
}

test_union :: ()
{
    // ti := type_info(K);
    print("\n---\n%\n---\n", type_info(Key).*);
    print("\n---\n%\n---\n", type_info(Key).runtime_size);
    a: Key;
    b: u8;
    print(">%\n", a == b);
    print(">%\n", a != Keys.None);

    c: string = "";
    print(">%\n", a == to_key(c));

    d: []u8 = xx "";
    print(">%\n", a == to_key(d));

    top := "┌───┐";
    btm := "└───┘";
    print(">%<\n", top);
    print(">%<\n", btm);

    str := "abcd";
    tok := to_key(str);
    tos := to_string(tok);
    
    print("1:%:\n", str);
    print("2:");
    for 0..7 {
        val := tok & 0xFF;
        tok >>=8 ;
        print("% ", FormatInt.{value=val, base=16, minimum_digits=2});
    }
    print(":\n");
    print("3:%:\n", tos);
   
}
#run test_union();

// Terminal action codes are encoded with values incompatible with UTF-8 to avoid collisions.


initialized := false;

// input_buffer    : [64] u8; // TODO FIXME Input buffer is too small!!!
input_buffer    : [8] u8; // TODO FIXME Input buffer is too small!!!
input_string    : string;
input_override  : Key;

#run {
    // Some tests.
    assert(input_buffer.count >= 6, "The input buffer size must be capable to hold an entire terminal (6 bytes) or UTF8 (4 bytes) code.");
}

assert_is_initialized :: inline () {
  assert(initialized, "TUI is not ready.");  
}

set_next_key :: (key: Key) {
    assert_is_initialized();
    input_override = key;
}

get_key :: (timeout_milliseconds: s32 = -1) -> Key {
    assert_is_initialized();
    
    // BBBB BBBB & 1100 0000 == 10XX XXXX -> is continuation byte
    is_utf8_continuation_byte :: inline (byte: u8) -> bool {
       return (byte & 0xC0) == 0x80;
    }

    // BBBB BBBB & 1110 0000 == 110X XXXX -> 1 initial + 1 continuation byte
    // BBBB BBBB & 1111 0000 == 1110 XXXX -> 1 initial + 2 continuation byte
    // BBBB BBBB & 1111 1000 == 1111 0XXX -> 1 initial + 3 continuation byte
    count_utf8_bytes :: inline (byte: u8) -> int {
        if (byte & 0xE0) == 0xC0 return 1+1;
        if (byte & 0xF0) == 0xE0 return 1+2;
        if (byte & 0xF8) == 0xF0 return 1+3;
        return 1;
    }
    
    if input_override != xx Keys.None {
        defer input_override = xx Keys.None;
        return input_override;
    }

    if OS_was_terminal_resized() return xx Keys.Resize;

    // FIXME Old version...
    // if input_string.count > 0 {
        // defer advance(*input_string, 1);
        // return input_string[0];
    // }
    // FIXME New version...
    if input_string.count > 0 #no_abc { // TODO Some trickery requires no_abc... which is not that nice in this case...
        utf8_bytes := count_utf8_bytes(input_string[0]);

        // TODO We're assuming the terminal buffer contains the entirety of what we need to read for the UTF8 symbols.
        if utf8_bytes > input_string.count {

            diff := utf8_bytes - input_string.count;

            // TODO Test this and make sure it's working...drop the following lines using Ctrl+V to fill the terminal buffer at once:
            // d€€€a
            // 1234567890123456789012345678901234567890
            print("<WoW>");
        
            // Copy buffered bytes to the start, and read the remaining ones from input.
            for 0..input_string.count-1 {
                input_buffer[it] = input_string[it];
            }
            aaa := OS_read_input(input_buffer.data + input_string.count, utf8_bytes-input_string.count); // TODO Does not check for read errors.
            assert(aaa == diff, "READ MORE THAN EXPECTED");
            input_string.data = input_buffer.data;
            input_string.count = utf8_bytes;
        }

        to_parse := input_string;
        to_parse.count = utf8_bytes;
        key := to_key(to_parse);
        
        advance(*input_string, utf8_bytes);
        return key;
    }

    is_input_available := OS_wait_for_input(timeout_milliseconds);

    if OS_was_terminal_resized() return xx Keys.Resize;

    // FIXME Old version...
    // if is_input_available {
        // bytes_read := OS_read_input(input_buffer.data, input_buffer.count); // TODO Does not check for read errors.
        // if bytes_read > 0 {
            // input_string.data = input_buffer.data;
            // input_string.count = bytes_read;
            // defer advance(*input_string, 1);
            // return input_string[0];
        // }
    // }
    // FIXME New version...
    if is_input_available {
        bytes_read := OS_read_input(input_buffer.data, input_buffer.count); // TODO Does not check for read errors.
        if bytes_read > 0 {
            input_string.data = input_buffer.data;
            input_string.count = bytes_read;
            utf8_bytes := count_utf8_bytes(input_string[0]);

            assert(utf8_bytes <= input_string.count, "The input buffer is too small."); // TODO Improve error message.

            // TODO This is only being done after the OS_wait_for_input... for now!
            to_parse := input_string;
            to_parse.count = utf8_bytes;
            
            // Must be a terminal escape sequence.
            if utf8_bytes == 1 && input_string[0] == #char "\e" {
                to_parse.count = ifx input_string.count > 6 then 6 else input_string.count; // TODO We should look into the input_string and search for the following escape sequence or somehting!?
            }
            
            key := to_key(to_parse);
            advance(*input_string, to_parse.count);
            return key;
            
            /// /// /// /// /// /// /// /// ///
            // DEBUG
            // br, bc := get_cursor_position();
            // column := 3;
            // row += 1;
            // nr, rc := get_terminal_size();
            // 
            // if row >= (rc - 5) then row = 5;
            //
            // set_cursor_position(row, column);
            // for 0..input_string.count-1 {
                // print("%:% | ",
                    // FormatInt.{base= 2, minimum_digits = 8, value = input_string[it]},
                    // FormatInt.{base= 16, minimum_digits = 2, value = input_string[it]},
                // ); // TODO DEBUG
            // }
            // set_cursor_position(br, bc);
            /// /// /// /// /// /// /// /// ///

        }
    }
    return xx Keys.None;
}

get_str :: (count_limit: int = -1, allocator: Allocator = temp) -> string {
    assert_is_initialized();
    assert(allocator.proc != null, "Argument 'allocator.proc' has invalid null value.");
    
    if count_limit < 0 {
        builder: String_Builder();
        builder.allocator = allocator;
        init_string_builder(*builder);
        
        while(1) {
            buffer := get_current_buffer(*builder);
            buffer_data := get_buffer_data(buffer);
            buffer.count = OS_read_input(buffer_data, buffer.allocated); // TODO Does not check for read errors.
            if buffer.count < buffer.allocated break;
            expand(*builder);
        }
        return builder_to_string(*builder, allocator);
    }
    else {
        buffer := alloc_string(count_limit, allocator);
        buffer.count = OS_read_input(buffer.data, count_limit);
        return buffer;
    }
}

start :: () {
    if initialized == true return;

    input_string.data   = input_buffer.data;
    input_string.count  = 0;
    input_override      = xx Keys.None;
    
    write_strings(Commands.HideCursor, Commands.SaveCursorPosition, Commands.AlternateScreenBuffer, Commands.SetUTF8);
    OS_prepare_terminal();
    
    initialized = true;
}

stop :: () {
    if initialized == false return;
    initialized = false;
    
    OS_reset_terminal();
    write_strings(Commands.MainScreenBuffer, Commands.RestoreCursorPosition, Commands.ShowCursor);
}

flush_input :: () {
    OS_flush_input();
}

// WIP WIP WIP
// set_style :: () {
    // print("", Commands.) --
// }

draw_box :: (x: int, y: int, width: int, height: int) {
    assert_is_initialized();

    // TODO Check if using a String_Builder improves performance (measure it)!
    // TODO Validate input parameters against the terminal size.
    assert(x > 0 && y > 0 && width > 1 && height > 1, "Invalid arguments.");

    auto_release_temp();
    
    tmp_string: string;
    
    tmp_string = tprint(Commands.SetCursorPosition, y, x);
    write_strings(
        Commands.DrawingMode,
        tmp_string,
        Drawings.CornerTL
        );

    for 1..width-2 {
        write_string(Drawings.LineH);
    }
    write_string(Drawings.CornerTR);

    for idx: y+1..y+height-2 {
        tmpL := tprint(Commands.SetCursorPosition, idx, x);
        tmpR := tprint(Commands.SetCursorPosition, idx, x+width-1);
        write_strings(
            tmpL,
            Drawings.LineV,
            tmpR,
            Drawings.LineV);
    }

    tmpBL := tprint(Commands.SetCursorPosition, y+height-1, x);
    write_strings(
        tmpBL,
        Drawings.CornerBL);
    for 1..width-2 {
        write_string(Drawings.LineH);
    }
    write_string(Drawings.CornerBR);
    
    write_string(Commands.TextMode);
}

// TODO Maybe rename to "clear()"
clear_terminal :: inline () {
    assert_is_initialized();
    write_string(Commands.ClearScreen);
}

// TODO Maybe rename to "get_size()"
get_terminal_size :: () -> rows: int, columns: int {
    assert_is_initialized();
    rows, columns: int = ---;
    #if OS == .WINDOWS {
        rows, columns = OS_get_terminal_size();
    }
    else {
        auto_release_temp();

        flush_input();
        write_string(Commands.QueryWindowSizeInChars);
        input := get_str(64);

        // Expected response format: \e[8;<r>;<c>t
        // where <r> is the number of rows and <c> of columns.
        FORMAT :: "\e[8;<r>;<c>t";
        
        // Discard head noise.
        while input.count >= 3 && (input[0] != FORMAT[0] || input[1] != FORMAT[1] || input[2] != FORMAT[2]) {
            advance(*input);
        }

        // Discard tail noise.
        while input.count >= 3 && input[input.count-1] != FORMAT[FORMAT.count-1] {
            input.count -= 1;
        }
        
        assert(input.count >= 3 &&
            input[0] == FORMAT[0] && input[1] == FORMAT[1] && input[2] == FORMAT[2] && input[input.count-1] == FORMAT[FORMAT.count-1],
            "Query window size in chars returned invalid response.");

        parts := split(input, ";");
        rows = parse_int(*parts[1]);
        columns = parse_int(*parts[2]);
    }
    return rows, columns;
}

set_cursor_position :: (row: int, column: int) {
    assert_is_initialized();
    auto_release_temp();
    tmp_string := tprint(Commands.SetCursorPosition, row, column);
    write_string(tmp_string);
}

get_cursor_position :: () -> row: int, column: int {
    assert_is_initialized();
    
    auto_release_temp();

    flush_input();
    write_string(Commands.QueryCursorPosition);
    input := get_str(64);

    // Expected response format: \e[<r>;<c>R
    // where <r> is the number of rows and <c> of columns.
    FORMAT :: "\e[<r>;<c>R";

    // Discard head noise.
    while input.count >= 2 && (input[0] != FORMAT[0] || input[1] != FORMAT[1]) {
        advance(*input);
    }

    // Discard tail noise.
    while input.count >= 2 && input[input.count-1] != FORMAT[FORMAT.count-1] {
        input.count -= 1;
    }

    assert(input.count >= 2 &&
        input[0] == FORMAT[0] && input[1] == FORMAT[1] && input[input.count-1] == FORMAT[FORMAT.count-1],
        "Query cursor position returned invalid response.");
    
    
    advance(*input, 2);
    parts := split(input, ";");
    row := parse_int(*parts[0]);
    column := parse_int(*parts[1]);
    return row, column;
}

set_terminal_title :: (title: string) {
    assert_is_initialized();
    print(Commands.SetWindowTitle, title);
}


#if OS == .WINDOWS {
    // Prototyping zone... keep clear!
}
else #if OS == .LINUX || OS == .MACOS {
    // Prototyping zone... keep clear!
}