#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 {
    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 {
    EnterAlternateBuffer    :: "\e[?1049h";
    EnterMainBuffer         :: "\e[?1049l";

    EnterDrawingMode        :: "\e(0";
    EnterNormalMode         :: "\e(B";
    ClearScreen             :: "\e[2J";
    ClearLine               :: "\e[2K";

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

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

    // 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.
    
}

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

// Let's return keys with 32bits so we can merge up to 4bytes and support UTF-8 encoding.
Key :: u32;

// Terminal action codes are encoded with values incompatible with UTF-8 to avoid collisions.
Keys :: enum Key {
    None    :: 0xFF000000;
    Resize  :: 0xFF000001;
}

initialized := false;

input_buffer    : [64] u8;
input_string    : string;
input_override  : Key;


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

get_key :: (timeout_milliseconds: s32 = -1) -> Key {

    /*
    TODO WIP Implement UTF-8 support, i.e., merge continuation bytes if needed:

    key = arg[0]
    while is_last_utf8_byte(buffer[0]) == false {
        key = key << 8
        advance(buffer)
        key |= buffer[0]
        TODO Sometimes we may not have all the necessary bytes in the buffer... and we may need to fetch some more into it. How to do it?
    }
    advance(arg)
    */ 

    if input_override != xx Keys.None {
        defer input_override = xx Keys.None;
        return input_override;
    }

    if OS_was_terminal_resized() return xx Keys.Resize;
    
    if input_string.count > 0 {
        defer advance(*input_string, 1);
        return input_string[0];
    }

    is_input_available := OS_wait_for_input(timeout_milliseconds);

    if OS_was_terminal_resized() return xx Keys.Resize;

    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];
        }
    }
    return xx Keys.None;
}

get_str :: (count_limit: int = -1, allocator: Allocator = temp) -> string {
    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;
    
    OS_prepare_terminal();
    write_strings(Commands.HideCursor, Commands.SaveCursorPosition, Commands.EnterAlternateBuffer, Commands.SetUTF8);
    
    initialized = true;
}

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

flush_input :: () {
    // TODO
}

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

    // 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.EnterDrawingMode,
        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.EnterNormalMode);
}

// TODO Maybe rename to "clear()"
clear_terminal :: inline () {
    assert(initialized, "TUI is not ready.");
    write_string(Commands.ClearScreen);
}

// TODO Maybe rename to "get_size()"
get_terminal_size :: () -> rows: int, columns: int {
    assert(initialized, "TUI is not ready.");
    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 message format: [8;<r>;<c>t
        // where <r> is the number of rows and <c> of columns.
        assert(
            input[0] == #char "\e" &&
            input[1] == #char "[" &&
            input[2] == #char "8",
            //input[input.count-1] == #char "t",
            "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(initialized, "TUI is not ready.");
    auto_release_temp();
    tmp_string := tprint(Commands.SetCursorPosition, row, column);
    write_string(tmp_string);
}

get_cursor_position :: () -> row: int, column: int {
    assert(initialized, "TUI is not ready."); // TODO Should I use this inside each and every procedure?

    auto_release_temp();

    flush_input();
    write_string(Commands.QueryCursorPosition);

    input := get_str(64);

    // Expected message format: \e[<r>;<c>R
    // where <r> is the number of rows and <c> of columns.
    assert(
        input[0] == #char "\e" &&
        input[1] == #char "[" &&
        input[input.count-1] == #char "R",
        "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;
}


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