#ifndef LEXER_H
#define LEXER_H

#include <stdlib.h>

#include "./token.h"
#include "./str.h"

struct lexer {
	struct str in;
	size_t pos;
	size_t rpos;
	char c;
};

struct lexer lexer_create(struct str in);
void lexer_read_char(struct lexer *l);

struct token lexer_next_token(struct lexer *l);

struct str lexer_read_ident(struct lexer *l);
struct str lexer_read_str_lit(struct lexer *l);
struct str lexer_read_int_lit(struct lexer *l);

enum token_type_enum lexer_lookup_ident(struct str ident);
void lexer_skip_whitespace(struct lexer *l);

bool _lexer_is_letter(char c);
bool _lexer_is_number(char c);

#if defined(IMP) || defined(LEXER_IMP)

struct lexer 
lexer_create(struct str in)
{
	struct lexer l = {0};
	l.in = in;
	lexer_read_char(&l);
	return l;
}

void 
lexer_read_char(struct lexer *l)
{
	if ( l->rpos >= l->in.size ) {
		l->c = '\0';
	} else {
		l->c = l->in.data[l->rpos];
	}
	l->pos = l->rpos;
	++l->rpos;
}

struct token 
lexer_next_token(struct lexer *l)
{
#define _LEXER_CUR_CHAR str_slice(l->in, l->pos, l->pos+1)

	struct token t = TOKEN_ILLEGAL;

	lexer_skip_whitespace(l);

	switch ( l->c ) {
	case '=':  t = token_create(TT_ASSIGN,    _LEXER_CUR_CHAR); break;
	case ';':  t = token_create(TT_SEMICOLON, _LEXER_CUR_CHAR); break;
	case '(':  t = token_create(TT_LPAREN,    _LEXER_CUR_CHAR); break;
	case ')':  t = token_create(TT_RPAREN,    _LEXER_CUR_CHAR); break;
	case ',':  t = token_create(TT_COMMA,     _LEXER_CUR_CHAR); break;
	case '*':  t = token_create(TT_ASTERISK,  _LEXER_CUR_CHAR); break;
	case '-':  t = token_create(TT_DASH,      _LEXER_CUR_CHAR); break;
	case '.':  t = token_create(TT_DOT,       _LEXER_CUR_CHAR); break;
	case '+':  t = token_create(TT_PLUS,      _LEXER_CUR_CHAR); break;
	case '{':  t = token_create(TT_LBRACE,    _LEXER_CUR_CHAR); break;
	case '}':  t = token_create(TT_RBRACE,    _LEXER_CUR_CHAR); break;
	case '<':  t = token_create(TT_LABRACKET, _LEXER_CUR_CHAR); break;
	case '>':  t = token_create(TT_RABRACKET, _LEXER_CUR_CHAR); break;
	case '\'': t = token_create(TT_SQUOTE,    _LEXER_CUR_CHAR); break;
	case '"':
		t = token_create(TT_STR_LIT, lexer_read_str_lit(l));
		return t;
		break;
	case '\0': t = token_create(TT_EOF, STR_EMPTY); break;
	default: 
		if ( _lexer_is_letter(l->c) ) {
			struct str ident = lexer_read_ident(l);
			t = token_create(lexer_lookup_ident(ident), ident);
			return t;
		}
		if ( _lexer_is_number(l->c) ) {
			return token_create(TT_INT_LIT, lexer_read_int_lit(l));
		}
		break;
	}

	lexer_read_char(l);

	return t;

#undef _LEXER_CUR_CHAR
}

struct str 
lexer_read_ident(struct lexer *l)
{
	size_t pos = l->pos;
	while ( _lexer_is_letter(l->c) ) {
		lexer_read_char(l);
	}
	return str_slice(l->in, pos, l->pos);
}

struct str
lexer_read_str_lit(struct lexer *l)
{
	size_t pos = l->pos;
	lexer_read_char(l);
loop:
	switch ( l->c ) {
	case '"':
	case '\0':
		break;

	default:
		lexer_read_char(l);
		goto loop;
		break;
	}

	lexer_read_char(l);
	return str_slice(l->in, pos+1, l->pos-1);
}

struct str
lexer_read_int_lit(struct lexer *l)
{
	size_t pos = l->pos;
	while ( _lexer_is_number(l->c) ) {
		lexer_read_char(l);
	}
	return str_slice(l->in, pos, l->pos);
	
}

enum token_type_enum
lexer_lookup_ident(struct str ident)
{
	if ( ident.size < 3 ) {
		return TT_IDENT;
	}

	switch ( ident.data[0] ) {
	case 'i':
		if ( str_eq_cstr(ident, "int", 3) ) {
			return TT_TYPE;
		}
		if ( str_eq_cstr(ident, "include", 7) ) {
			return TT_INCLUDE;
		}
		break;
	case 'c':
		if ( str_eq_cstr(ident, "char", 4) ) {
			return TT_TYPE;
		}
		if ( str_eq_cstr(ident, "const", 5) ) {
			return TT_CONST;
		}
		break;
	case 'r':
		if ( str_eq_cstr(ident, "return", 6) ) {
			return TT_RETURN;
		}
		break;
	}


	return TT_IDENT;
}

void 
lexer_skip_whitespace(struct lexer *l)
{
loop:
	switch ( l->c ) {
	case ' ':
	case '\t':
	case '\r':
	case '\n':
		lexer_read_char(l);
		goto loop;
	}

	return;
}

bool
_lexer_is_letter(char c)
{
	return ( c >= 0x41 && c <= 0x5A ) \
	       || ( c >= 0x61 && c <= 0x7A ) \
	       || c == 0x5F;
}

bool
_lexer_is_number(char c)
{
	return ( c >= '0' && c <= '9' );
}

#endif /* defined(IMP) || defined(LEXER_IMP) */

#endif /* LEXER_H */