#include "parse.h"

#include <assert.h>
#include <string.h>

void parse_init(am_t *am, parse_ctx_t *out)
{
	out->am = am;
	out->state = PARSE_STATE_INIT;
	out->sp = out->stack + PARSE_MAX_DEPTH - 1;
}

static void push_state(parse_ctx_t *ctx, parse_state_t state)
{
	assert(ctx->sp >= ctx->stack);
	*ctx->sp-- = state;
}

static parse_state_t pop_state(parse_ctx_t *ctx)
{
	assert(ctx->sp < ctx->stack + PARSE_MAX_DEPTH - 1);
	return *++ctx->sp;
}

static void append(parse_ctx_t *ctx, expr_t *expr)
{
	expr_t *list = ctx->am->expr;
	while (!list->is_atom)
		list = list->pair.cdr;
	assert(list->atom.type == ATOM_TYPE_EMPTY_LIST);

	list->is_atom = false;
	list->pair.car = expr;
	list->pair.cdr = expr_empty_list(ctx->am);
}

parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
{
	switch (ctx->state) {
	case PARSE_STATE_INIT:
		switch (token->type) {
		case TOKEN_TYPE_INTEGER:
			ctx->am->expr = expr_integer(ctx->am, token->integer);
			ctx->state = PARSE_STATE_DONE;
			break;
		case TOKEN_TYPE_SYMBOL:
			ctx->am->expr = expr_symbol(ctx->am, &token->symbol);
			ctx->state = PARSE_STATE_DONE;
			break;
		case TOKEN_TYPE_OPEN_PAREN:
			push_state(ctx, PARSE_STATE_DONE);
			ctx->am->expr = expr_empty_list(ctx->am);
			ctx->state = PARSE_STATE_LIST;
			break;
		case TOKEN_TYPE_CLOSE_PAREN:
			ctx->state = PARSE_STATE_ERROR;
			break;
		}
		break;

	case PARSE_STATE_LIST:
		switch (token->type) {
		case TOKEN_TYPE_INTEGER:
			append(ctx, expr_integer(ctx->am, token->integer));
			break;
		case TOKEN_TYPE_SYMBOL:
			append(ctx, expr_symbol(ctx->am, &token->symbol));
			break;
		case TOKEN_TYPE_OPEN_PAREN:
			am_push(ctx->am);
			push_state(ctx, PARSE_STATE_LIST);
			ctx->am->expr = expr_empty_list(ctx->am);
			ctx->state = PARSE_STATE_LIST;
			break;
		case TOKEN_TYPE_CLOSE_PAREN:
			ctx->state = pop_state(ctx);
			if (ctx->state == PARSE_STATE_LIST) {
				expr_t *expr = ctx->am->expr;
				am_pop(ctx->am);
				append(ctx, expr);
			}
			break;
		}
		break;

	case PARSE_STATE_DONE:
	case PARSE_STATE_ERROR:
		break;
	}

	assert(ctx->state != PARSE_STATE_INIT);
	return ctx->state;
}