#include <stdbool.h>
#include <stdio.h>
#include <stddef.h>

enum token_type {
    tok_ident,
    tok_param_ident,
    tok_int,
    tok_string,

    /* Symbols */
    tok_arrow,
    tok_backslash,
    tok_equal,
    tok_left_paren,
    tok_right_paren,
    tok_left_square,
    tok_right_square,
    tok_left_brace,
    tok_right_brace,
    tok_left_angle_bracket,
    tok_right_angle_bracket,
    tok_comma,
    tok_pipe,
    tok_colon,

    /* Keywords */
    tok_true,
    tok_false,
    tok_case,
    tok_let,
    tok_in,
    tok_match,
    tok_of,
    tok_def,
    tok_datatype,
    tok_alias,
    tok_typecheck,

    tok_eof,
};

struct token {
    enum token_type type;
    char *lexeme;
};

/* Gives a text description of a token type */
const char *token_descr(enum token_type tok);

struct location {
    size_t line;
    size_t col;
};

#define LEXEME_MAX_LEN 1024

struct lexer {
    /* Input stream to be lexed */
    FILE *in;
    /* Lookahead character */
    char cur;
    /* Internal buffer used to incrementally store lexemes */
    char buf[LEXEME_MAX_LEN];
    /* Number of character currently stored in buf */
    size_t buf_len;
    /* Source Location information */
    struct location loc;
};

/* Initialize lexer.
 * If there is an error, aborts the program.
 */
void init_lexer(struct lexer *lex, FILE *in);

/* Read next token, and store it in out.
 * Store the token location in loc.
 * If there is an error, aborts the program.
 */
void lex_next(struct lexer *lex, struct token *out, struct location *loc);