#include <stdlib.h>
#include <stdio.h>
#include "parser.h"

static struct token *get_token(struct parser *parser) {
    return lex_token(&parser->lexer);
}

static int token_is(struct parser *parser, enum token_type type) {
    return get_token(parser)->type == type;
}

static double token_num(struct parser *parser) {
    return get_token(parser)->val.num;
}

static enum math_fn token_fn(struct parser *parser) {
    return get_token(parser)->val.fn;
}

static void next_token(struct parser *parser) {
    lex_next(&parser->lexer);
}

static int accept_token(struct parser *parser, enum token_type type) {
    if (token_is(parser, type)) {
        next_token(parser);
        return 1;
    }
    return 0;
}

static void error_bad_alloc(struct parser *parser) {
    error_set(&parser->eb, ERR_BAD_ALLOC);
    error_printf(&parser->eb, "Out of memory\n");
}

static void error_expected_one_of(struct parser *parser, const int expected[]) {
    static const char* token_name[] = {
        "end of expression",
        "lexer error",
        "constant",
        "+",
        "-",
        "*",
        "/",
        "^",
        "x",
        "function name",
        "(",
        ")"
    };

    size_t i;

    enum token_type got = get_token(parser)->type;

    if (got == TOK_ERROR) {
        error_set(&parser->eb, lex_get_error(&parser->lexer));
        error_printf(&parser->eb, "Lexer error - %s", lex_get_error_text(&parser->lexer));
        return;
    }

    error_set(&parser->eb, ERR_INVALID_FUNCTION);
    error_printf(&parser->eb, "Syntax error - expected ");

    for (i = 0; expected[i] >= 0; ++i) {
        if (i > 0)
            error_printf(&parser->eb, ", ");

        error_printf(&parser->eb, "'%s'", token_name[expected[i]]);
    }

    error_printf(&parser->eb, " - but got '%s'\n", token_name[got]);

    lex_print_position(&parser->lexer, &parser->eb);
}

static void error_expected_single(struct parser *parser, enum token_type expected) {
    static int expected_arr[] = { -1, -1 };
    expected_arr[0] = expected;
    error_expected_one_of(parser, expected_arr);
}

static struct expr_node* parse_subexpression(struct parser *parser);

static struct expr_node* parse_bracketed(struct parser *parser) {
    struct expr_node* node;

    if (!accept_token(parser, TOK_LEFT_PAREN)) {
        error_expected_single(parser, TOK_LEFT_PAREN);
        return NULL;
    }

    if (!(node = parse_subexpression(parser)))
        return NULL;

    if (!accept_token(parser, TOK_RIGHT_PAREN)) {
        error_expected_single(parser, TOK_RIGHT_PAREN);
        node_free(node);
        return NULL;
    }

    return node;
}

static struct expr_node *parse_base(struct parser *parser) {
    struct expr_node *node, *inner;

    if (token_is(parser, TOK_NUMBER)) {
        double val = token_num(parser);
        next_token(parser);
        if (!(node = node_create_const(val))) {
            error_bad_alloc(parser);
            return NULL;
        }

        return node;
    }

    if (accept_token(parser, TOK_X)) {
        if (!(node = node_create_x())) {
            error_bad_alloc(parser);
            return NULL;
        }
        return node;
    }

    if (token_is(parser, TOK_FUNCTION)) {
        enum math_fn fn = token_fn(parser);
        next_token(parser);

        if (!(inner = parse_bracketed(parser)))
            return NULL;

        if (!(node = node_create_fn(fn, inner))) {
            node_free(inner);
            error_bad_alloc(parser);
            return NULL;
        }

        return node;
    }

    if (token_is(parser, TOK_LEFT_PAREN)) {
        return parse_bracketed(parser);
    }

    {
        static const int expected[] = { TOK_NUMBER, TOK_X, TOK_FUNCTION, TOK_LEFT_PAREN, -1 };
        error_expected_one_of(parser, expected);
    }

    return NULL;
}

static struct expr_node *parse_unary(struct parser *parser);

static struct expr_node *parse_factor(struct parser *parser) {
    struct expr_node* node, * new_node, * inner;

    if (!(node = parse_base(parser)))
        return NULL;

    if (accept_token(parser, TOK_POWER)) {
        if (!(inner = parse_unary(parser))) {
            node_free(node);
            return NULL;
        }

        if (!(new_node = node_create_pow(node, inner))) {
            error_bad_alloc(parser);
            node_free(node);
            node_free(inner);
            return NULL;
        }

        return new_node;
    }

    return node;
}

static struct expr_node* parse_unary(struct parser *parser) {
    if (accept_token(parser, TOK_MINUS)) {
        struct expr_node *node, *inner;
        
        if (!(inner = parse_factor(parser)))
            return NULL;

        if (!(node = node_create_neg(inner))) {
            error_bad_alloc(parser);
            node_free(inner);
            return NULL;
        }

        return node;
    }

    accept_token(parser, TOK_PLUS);
    return parse_factor(parser);
}

static struct expr_node *parse_term(struct parser *parser) {
    struct expr_node *node, *new_node, *inner;

    if (!(node = parse_unary(parser)))
        return NULL;

    while (1) {
        struct expr_node *(*create_node)(struct expr_node *left, struct expr_node *right);

        if (accept_token(parser, TOK_MULTIPLY))
            create_node = node_create_mult;
        else if (accept_token(parser, TOK_DIVIDE))
            create_node = node_create_div;
        else
            break;

        if (!(inner = parse_unary(parser))) {
            node_free(node);
            return NULL;
        }

        if (!(new_node = create_node(node, inner))) {
            error_bad_alloc(parser);
            node_free(node);
            node_free(inner);
            return NULL;
        }

        node = new_node;
    }

    return node;
}

static struct expr_node *parse_subexpression(struct parser *parser) {
    struct expr_node *node, *new_node, *inner;

    if (!(node = parse_term(parser)))
        return NULL;

    while (1) {
        struct expr_node *(*create_node)(struct expr_node *left, struct expr_node *right);

        if (accept_token(parser, TOK_PLUS))
            create_node = node_create_add;
        else if (accept_token(parser, TOK_MINUS))
            create_node = node_create_sub;
        else
            break;

        if (!(inner = parse_term(parser))) {
            node_free(node);
            return NULL;
        }

        if (!(new_node = create_node(node, inner))) {
            error_bad_alloc(parser);
            node_free(node);
            node_free(inner);
            return NULL;
        }

        node = new_node;
    }

    return node;
}

static struct expr_node *parse_expression(struct parser *parser) {
    struct expr_node *node;

    if (!(node = parse_subexpression(parser)))
        return NULL;

    if (!token_is(parser, TOK_EOF)) {
        error_expected_single(parser, TOK_EOF);
        node_free(node);
        return NULL;
    }

    return node;
}

void parser_init(struct parser *parser) {
    error_buffer_init(&parser->eb);
}

struct expr_node *parser_parse(struct parser *parser, const char *str) {
    lex_init(&parser->lexer, str);
    return parse_expression(parser);

}

enum error_code parser_get_error(const struct parser *parser) {
    return error_get(&parser->eb);
}

const char *parser_get_error_text(const struct parser *parser) {
    return error_get_text(&parser->eb);
}