#include "parser.h"
#include "config.h"
#include "tokenizer.h"

typedef struct {
	SandTokenizer tokenizer;
	SandToken previous;
	SandToken current;

	SandAllocator *a;
	SandState *S;
} Parser;

// Report an error at the given token and enter panic mode.
static void error_at(Parser *parser, SandToken token, const char *message) {
	sand_print_diagnostic(parser->S, token.location, SAND_DIAGNOSTIC_ERROR, "");
}


// Same as `error_at` except using the parser's current token.
static void error_at_current(Parser *parser, const char *message) {
	error_at(parser, parser->current, message);
}

static void advance(Parser *parser) {
	parser->previous = parser->current;

	while (true) {
		parser->current = sand_get_next_token(&parser->tokenizer);
		if (parser->current.kind == SAND_TOKEN_ERROR) {
			// `content` is going to be NULL-terminated because it will always point to a C string literal for error tokens.
			error_at_current(parser, parser->current.content);
		} else {
			break;
		}
	}
}

static SandToken peek(const Parser *parser) {
	return parser->current;
}

static bool match(Parser *parser, SandTokenKind expected) {
	if (peek(parser).kind == expected) {
		advance(parser);
		return true;
	} else {
		return false;
	}
}

static void consume(Parser *parser, SandTokenKind expected, const char *error) {
	if (!match(parser, expected)) {
		error_at_current(parser, error);
	}
}

SandAst *sand_parse(SandState *S, SandAllocator *a, const char *source, size_t source_length, const char *filename) {
	Parser parser;
	parser.a = a;
	parser.S = S;

	parser.tokenizer = sand_create_tokenizer(source, source_length, filename);
	advance(&parser); // Prime the pump on the tokenizer.

	// Parse the document.
	SandAst *expr = expression(&parser);
	consume(&parser, SAND_TOKEN_EOF, "Expected end of expression");

	return expr;
}