//! VERSION: 0.0.2
//! This module provides functionality to the uncooked terminal.
//! The following termios setup was retrieved from zig.news[1] on 2024-08-04
//! 10:57:50.
//! - [1]: https://zig.news/lhp/want-to-create-a-tui-application-the-basics-of-uncooked-terminal-io-17gm

const std = @import("std");
const os = std.os;
const fs = std.fs;
const mem = std.mem;

/// Key enum. This is meant to capture any and all ascii input from the user.
/// This can only capture ascii input and some simple escape sequences.
pub const Key = enum {
    Null,
    StartOfHeading,
    StartOfText,
    EndOfText,
    EndOfTransmission,
    Enquiry,
    Acknowledge,
    Bell,
    Backspace,
    Tab,
    NewLine,
    VerticalTab,
    NewPage,
    CarriageReturn,
    ShiftOut,
    ShiftIn,
    DataLinkEscape,
    DeviceControl1,
    DeviceControl2,
    DeviceControl3,
    DeviceControl4,
    NegativeAcknowledgement,
    SynchronousIdle,
    EndOfTransmissionBlock,
    Cancel,
    EndOfMedium,
    Substitute,
    Escape,
    FileSeparator,
    GroupSeparator,
    RecordSeparator,
    UnitSeparator,
    Space,
    ExclamationMark,
    QuotationMark,
    NumberSign,
    DollarSign,
    PercentSign,
    Ampersand,
    Apostrophe,
    LParen,
    RParen,
    Asterisk,
    PlusSign,
    Comma,
    MinusSign,
    Period,
    ForwardSlash,
    Zero,
    One,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Eight,
    Nine,
    Colon,
    SemiColon,
    LessThan,
    Equal,
    GreaterThan,
    QuestionMark,
    At,
    A,
    B,
    C,
    D,
    E,
    F,
    G,
    H,
    I,
    J,
    K,
    L,
    M,
    N,
    O,
    P,
    Q,
    R,
    S,
    T,
    U,
    V,
    W,
    X,
    Y,
    Z,
    LBracket,
    BackwardSlash,
    RBracket,
    Caret,
    UnderScore,
    Backtick,
    a,
    b,
    c,
    d,
    e,
    f,
    g,
    h,
    i,
    j,
    k,
    l,
    m,
    n,
    o,
    p,
    q,
    r,
    s,
    t,
    u,
    v,
    w,
    x,
    y,
    z,
    LBrace,
    Pipe,
    RBrace,
    Tilde,
    //
    ArrowLeft,
    ArrowRight,
    ArrowUp,
    ArrowDown,
};

/// Key errors.
const KeyError = error{UnkownKey};

/// Waits until the user presses a key and returns the pressed key as the `Key`
/// enum.
pub fn get_key() !Key {
    var tty: fs.File = try fs.cwd().openFile("/dev/tty", .{ .mode = fs.File.OpenMode.read_write });
    defer tty.close();

    const original_termios = try os.tcgetattr(tty.handle);
    var raw = original_termios;

    raw.lflag &= ~@as(os.system.tcflag_t, os.system.ECHO | os.system.ICANON | os.system.ISIG | os.system.IEXTEN);
    raw.iflag &= ~@as(os.system.tcflag_t, os.system.IXON | os.system.ICRNL | os.system.BRKINT | os.system.INPCK | os.system.ISTRIP);
    raw.oflag &= ~@as(os.system.tcflag_t, os.system.OPOST);
    raw.cflag |= os.system.CS8;

    raw.cc[os.system.V.TIME] = 0;
    raw.cc[os.system.V.MIN] = 1;

    os.tcsetattr(tty.handle, .FLUSH, raw) catch {};
    var flushed: bool = true;
    defer {
        if (flushed) {
            os.tcsetattr(tty.handle, .FLUSH, original_termios) catch {};
        } else {
            os.tcsetattr(tty.handle, .NOW, original_termios) catch {};
        }
    }

    tty.writeAll("\x1B[s") catch {}; // Save cursor position.
    tty.writeAll("\x1B[?25l") catch {}; // Hide the cursor.
    defer tty.writeAll("\x1B[u") catch {}; // Restore cursor position.

    var buffer: [1]u8 = undefined;
    _ = tty.read(&buffer) catch 0;

    const ret = switch (buffer[0]) {
        0 => .Null,
        1 => .StartOfHeading,
        2 => .StartOfText,
        3 => .EndOfText,
        4 => .EndOfTransmission,
        5 => .Enquiry,
        6 => .Acknowledge,
        7 => .Bell,
        8 => .Backspace,
        9 => .Tab,
        10 => .NewLine,
        11 => .VerticalTab,
        12 => .NewPage,
        13 => .CarriageReturn,
        14 => .ShiftOut,
        15 => .ShiftIn,
        16 => .DataLinkEscape,
        17 => .DeviceControl1,
        18 => .DeviceControl2,
        19 => .DeviceControl3,
        20 => .DeviceControl4,
        21 => .NegativeAcknowledgement,
        22 => .SynchronousIdle,
        23 => .EndOfTransmissionBlock,
        24 => .Cancel,
        25 => .EndOfMedium,
        26 => .Substitute,
        27 => esc: {
            raw.cc[os.system.V.TIME] = 1;
            raw.cc[os.system.V.MIN] = 0;

            flushed = false;
            os.tcsetattr(tty.handle, .NOW, raw) catch {};

            var esc_buffer: [8]u8 = undefined;
            const esc_read = try tty.read(&esc_buffer);

            raw.cc[os.system.V.TIME] = 0;
            raw.cc[os.system.V.MIN] = 1;

            if (esc_read == 0) {
                break :esc Key.Escape;
            } else if (mem.eql(u8, esc_buffer[0..esc_read], "[A")) {
                break :esc Key.ArrowUp;
            } else if (mem.eql(u8, esc_buffer[0..esc_read], "[B")) {
                break :esc Key.ArrowDown;
            } else if (mem.eql(u8, esc_buffer[0..esc_read], "[D")) {
                break :esc Key.ArrowLeft;
            } else if (mem.eql(u8, esc_buffer[0..esc_read], "[C")) {
                break :esc Key.ArrowRight;
            } else {
                return KeyError.UnkownKey;
            }
        },
        28 => .FileSeparator,
        29 => .GroupSeparator,
        30 => .RecordSeparator,
        31 => .UnitSeparator,
        32 => .Space,
        33 => .ExclamationMark,
        34 => .QuotationMark,
        35 => .NumberSign,
        36 => .DollarSign,
        37 => .PercentSign,
        38 => .Ampersand,
        39 => .Apostrophe,
        40 => .LParen,
        41 => .RParen,
        42 => .Asterisk,
        43 => .PlusSign,
        44 => .Comma,
        45 => .MinusSign,
        46 => .Period,
        47 => .ForwardSlash,
        48 => .Zero,
        49 => .One,
        50 => .Two,
        51 => .Three,
        52 => .Four,
        53 => .Five,
        54 => .Six,
        55 => .Seven,
        56 => .Eight,
        57 => .Nine,
        58 => .Colon,
        59 => .SemiColon,
        60 => .LessThan,
        61 => .Equal,
        62 => .GreaterThan,
        63 => .QuestionMark,
        64 => .At,
        65 => .A,
        66 => .B,
        67 => .C,
        68 => .D,
        69 => .E,
        70 => .F,
        71 => .G,
        72 => .H,
        73 => .I,
        74 => .J,
        75 => .K,
        76 => .L,
        77 => .M,
        78 => .N,
        79 => .O,
        80 => .P,
        81 => .Q,
        82 => .R,
        83 => .S,
        84 => .T,
        85 => .U,
        86 => .V,
        87 => .W,
        88 => .X,
        89 => .Y,
        90 => .Z,
        91 => .LBracket,
        92 => .BackwardSlash,
        93 => .RBracket,
        94 => .Caret,
        95 => .UnderScore,
        96 => .Backtick,
        97 => .a,
        98 => .b,
        99 => .c,
        100 => .d,
        101 => .e,
        102 => .f,
        103 => .g,
        104 => .h,
        105 => .i,
        106 => .j,
        107 => .k,
        108 => .l,
        109 => .m,
        110 => .n,
        111 => .o,
        112 => .p,
        113 => .q,
        114 => .r,
        115 => .s,
        116 => .t,
        117 => .u,
        118 => .v,
        119 => .w,
        120 => .x,
        121 => .y,
        122 => .z,
        123 => .LBrace,
        124 => .Pipe,
        125 => .RBrace,
        126 => .Tilde,
        else => {
            return KeyError.UnkownKey;
        },
    };

    return ret;
}