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// Copyright (C) 2023, Jakob Wakeling

// All rights reserved.

#include "lex.h"

#include "util/log.h"

#include "util/stack.h"

#include "util/util.h"

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

char *tok_ks[] = {

	"TK_VOID", "TK_EOF", "TK_WORD", "TK_END",

	"TK_PIPE", "TK_RIN", "TK_ROUT", "TK_RAPP",

};

#define is_space(c) (c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\t' || c == '\v')

/* Initialise a lexer. */

lex lex_init(char *str, u64 len) {

	lex l = { .s = str, .p = str, .q = str + len }; lex_next(&l); return l;

}

#define P (l->p) /* Pointer to the Current Character */

#define Q (l->q) /* Pointer to EOF */

#define T (l->t) /* Current Token */

/* Return the current token. */

tok lex_peek(lex *l) { return T; }

/* Lex the next token, and return the current one. */

tok lex_next(lex *l) {

	if (T.k == TK_EOF) { return T; }

	tok t = T; T = (tok){ .k = TK_VOID };

	/* Skip null characters and whitespace */

	skip:; for (; P != Q && (!P[0] || is_space(P[0])); P += 1);

	/* Return the current token immediately if EOF or END is reached */

	if (P == Q) { T.k = TK_EOF; return t; }

	if (P[0] == '\n' || P[0] == ';') { P += 1; T.k = TK_END; return t; }

	/* Skip comments */

	if (P[0] == '#') {

		for (P += 1; P != Q && P[0] != '\n'; P += 1);

		if (P[0] == '\n') { P += 1; } goto skip;

	}

	switch (P[0]) {

	case '|': { T.k = TK_PIPE; P += 1; } break;

	case '<': { T.k = TK_RIN;  P += 1; } break;

	case '>': switch (P[1]) {

		default:  { T.k = TK_ROUT; P += 1; } break;

		case '>': { T.k = TK_RAPP; P += 2; } break;

	} break;

	/* Handle words, TODO review quotes and substitutions */

	default: {

		stack s = stack_init(sizeof (char), NULL);

		for (; P != Q && P[0] != '\n' && P[0] != ';' && P[0] != ' '; P += 1) {

			if (P[0] == '|' || P[0] == '<' || P[0] == '>') { break; }

			/* Handle single quotes */

			else if (P[0] == '\'') for (P += 1;; P += 1) {

				/* FIXME memory leak upon missing closing ', needs refinement */

				if (P == Q) { log_warn("Missing closing \'"); return t; }

				else if (P[0] == '\'') { break; }

				else { stack_push(&s, P[0]); }

			}

			/* Handle all other characters */

			else { stack_push(&s, P[0]); }

		}

		T.s = strndup(s.a, s.al); T.k = TK_WORD; stack_free(&s);

	} break;

	}

	return t;

}

/* Print lexer debug output. */

void lex_debug(lex *l) {

	for (tok t = lex_next(l); t.k != TK_EOF; free(t.s), t = lex_next(l)) {

		printf("%s \"%s\"\n", tok_ks[t.k], t.s);

	}

}