pub const Tag = enum {
    // Literals
    int_literal,
    float_literal,
    string_literal,
    raw_string_literal,

    // Identifiers and keywords
    identifier,
    kw_if,
    kw_else,
    kw_then,
    kw_true,
    kw_false,
    kw_enum,
    kw_case,
    kw_break,
    kw_continue,
    kw_while,
    kw_for,
    kw_return,
    kw_defer,
    kw_f32,
    kw_f64,
    kw_struct,
    kw_union,
    kw_xx,
    kw_and,
    kw_or,
    kw_Type, // Type (metatype keyword)
    kw_null, // null
    kw_push, // push
    kw_ufcs, // ufcs
    kw_in, // in
    kw_closure, // closure
    kw_protocol, // protocol
    kw_impl, // impl
    kw_Self, // Self (in protocol declarations)
    kw_inline, // inline (compile-time if/for/while)
    kw_callconv, // callconv (calling convention annotation)

    // Symbols
    colon, // :
    colon_colon, // ::
    colon_equal, // :=
    semicolon, // ;
    comma, // ,
    dot, // .
    dot_dot, // ..
    dollar, // $

    // Operators
    plus, // +
    minus, // -
    star, // *
    slash, // /
    equal, // =
    equal_equal, // ==
    bang, // !
    bang_equal, // !=
    less, // <
    less_equal, // <=
    greater, // >
    greater_equal, // >=
    plus_equal, // +=
    minus_equal, // -=
    star_equal, // *=
    slash_equal, // /=
    percent, // %
    percent_equal, // %=
    ampersand, // &
    ampersand_equal, // &=
    at, // @
    pipe, // |
    pipe_equal, // |=
    pipe_arrow, // |>
    caret, // ^
    caret_equal, // ^=
    question, // ?
    question_question, // ??
    question_dot, // ?.
    tilde, // ~
    less_less, // <<
    less_less_equal, // <<=
    greater_greater, // >>
    greater_greater_equal, // >>=

    // Delimiters
    l_paren, // (
    r_paren, // )
    l_brace, // {
    r_brace, // }
    l_bracket, // [
    r_bracket, // ]

    // Arrows
    arrow, // ->
    fat_arrow, // =>

    // Directives
    hash_run, // #run
    hash_import, // #import
    hash_insert, // #insert
    hash_builtin, // #builtin
    hash_compiler, // #compiler
    hash_foreign, // #foreign
    hash_library, // #library
    hash_framework, // #framework
    hash_using, // #using
    hash_include, // #include (inside #import c { ... })
    hash_source, // #source (inside #import c { ... })
    hash_define, // #define (inside #import c { ... })
    hash_flags, // #flags (inside #import c { ... })
    hash_inline, // #inline (protocol layout modifier)
    triple_minus, // ---

    // Special
    eof,
    invalid,

    pub fn lexeme(tag: Tag) ?[]const u8 {
        return switch (tag) {
            .colon => ":",
            .colon_colon => "::",
            .colon_equal => ":=",
            .semicolon => ";",
            .comma => ",",
            .dot => ".",
            .dot_dot => "..",
            .dollar => "$",
            .plus => "+",
            .minus => "-",
            .star => "*",
            .slash => "/",
            .equal => "=",
            .equal_equal => "==",
            .bang => "!",
            .bang_equal => "!=",
            .less => "<",
            .less_equal => "<=",
            .greater => ">",
            .greater_equal => ">=",
            .plus_equal => "+=",
            .minus_equal => "-=",
            .star_equal => "*=",
            .slash_equal => "/=",
            .percent => "%",
            .percent_equal => "%=",
            .ampersand => "&",
            .ampersand_equal => "&=",
            .at => "@",
            .pipe => "|",
            .pipe_equal => "|=",
            .pipe_arrow => "|>",
            .caret => "^",
            .caret_equal => "^=",
            .question => "?",
            .question_question => "??",
            .question_dot => "?.",
            .tilde => "~",
            .less_less => "<<",
            .less_less_equal => "<<=",
            .greater_greater => ">>",
            .greater_greater_equal => ">>=",
            .kw_null => "null",
            .l_paren => "(",
            .r_paren => ")",
            .l_brace => "{",
            .r_brace => "}",
            .l_bracket => "[",
            .r_bracket => "]",
            .arrow => "->",
            .fat_arrow => "=>",
            .triple_minus => "---",
            else => null,
        };
    }

    pub fn isTypeKeyword(tag: Tag) bool {
        return switch (tag) {
            .kw_f32, .kw_f64, .kw_Type, .kw_Self => true,
            else => false,
        };
    }
};

pub const Token = struct {
    tag: Tag,
    loc: Loc,

    pub const Loc = struct {
        start: u32,
        end: u32,
    };

    pub fn slice(self: Token, source: []const u8) []const u8 {
        return source[self.loc.start..self.loc.end];
    }
};

pub const keywords = std.StaticStringMap(Tag).initComptime(.{
    .{ "if", .kw_if },
    .{ "else", .kw_else },
    .{ "then", .kw_then },
    .{ "true", .kw_true },
    .{ "false", .kw_false },
    .{ "enum", .kw_enum },
    .{ "case", .kw_case },
    .{ "break", .kw_break },
    .{ "continue", .kw_continue },
    .{ "while", .kw_while },
    .{ "for", .kw_for },
    .{ "return", .kw_return },
    .{ "defer", .kw_defer },
    .{ "f32", .kw_f32 },
    .{ "f64", .kw_f64 },
    .{ "struct", .kw_struct },
    .{ "union", .kw_union },
    .{ "xx", .kw_xx },
    .{ "and", .kw_and },
    .{ "or", .kw_or },
    .{ "Type", .kw_Type },
    .{ "null", .kw_null },
    .{ "push", .kw_push },
    .{ "ufcs", .kw_ufcs },
    .{ "in", .kw_in },
    .{ "closure", .kw_closure },
    .{ "protocol", .kw_protocol },
    .{ "impl", .kw_impl },
    .{ "Self", .kw_Self },
    .{ "inline", .kw_inline },
    .{ "callconv", .kw_callconv },
});

pub fn getKeyword(bytes: []const u8) ?Tag {
    return keywords.get(bytes);
}

const std = @import("std");