#include "parser.h"
#include "lexer.h"
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

Expr* error_expr(Position pos, const char* message)
{
    Expr* node = malloc(sizeof(Expr));
    *node = (Expr) {
        .type = ExprTypeError,
        .error = (ErrorExpr) {
            .pos = pos,
            .message = strndup(message, strlen(message)),
        },
    };
    return node;
}

Expr* int_expr(int64_t value)
{
    Expr* node = malloc(sizeof(Expr));
    *node = (Expr) {
        .type = ExprTypeInt,
        .int_expr = (IntExpr) {
            .value = value,
        },
    };
    return node;
}

Expr* unary_expr(UnaryExprType type, Expr* subject)
{
    Expr* node = malloc(sizeof(Expr));
    *node = (Expr) {
        .type = ExprTypeUnary,
        .unary = (UnaryExpr) {
            .type = type,
            .subject = subject,
        },
    };
    return node;
}

Expr* binary_expr(BinaryExprType type, Expr* left, Expr* right)
{
    Expr* node = malloc(sizeof(Expr));
    *node = (Expr) {
        .type = ExprTypeBinary,
        .binary = (BinaryExpr) {
            .type = type,
            .left = left,
            .right = right,
        },
    };
    return node;
}

typedef struct {
    const char* text;
    size_t length;
    Lexer* lexer;
    Token current;
} Parser;

bool parser_done(Parser* parser)
{
    return parser->current.type == TokenTypeEof;
}

bool parser_current_is(Parser* parser, TokenType type)
{
    return !parser_done(parser) && parser->current.type == type;
}

void parser_step(Parser* parser)
{
    parser->current = lexer_next(parser->lexer);
}

Position parser_pos(Parser* parser)
{
    return (Position) {
        .index = parser->current.index,
        .line = parser->current.line,
        .col = parser->current.col,
    };
}

Expr* parser_expr(Parser* parser);

Expr* parser_unknown_token_error(Parser* parser)
{
    char buffer[128] = { 0 };
    snprintf(
        buffer, 128, "unknown char '%c'", parser->text[parser->current.index]
    );
    return error_expr(parser_pos(parser), buffer);
}

Expr* parser_operand(Parser* parser)
{
    if (parser_current_is(parser, TokenTypeInt)) {
        char buffer[24];
        strncpy(
            buffer, &parser->text[parser->current.index], parser->current.length
        );
        parser_step(parser);
        return int_expr(atol(buffer));
    } else if (parser_current_is(parser, TokenTypeEof)) {
        Position pos = parser_pos(parser);
        parser_step(parser);
        return error_expr(pos, "unexpected end-of-file");
    } else {
        Expr* error = parser_unknown_token_error(parser);
        parser_step(parser);
        return error;
    }
}

Expr* parser_group(Parser* parser)
{
    if (parser_current_is(parser, TokenTypeLParen)) {
        parser_step(parser);
        Expr* value = parser_expr(parser);
        if (!parser_current_is(parser, TokenTypeRParen)) {
            parser_step(parser);
            return error_expr(parser_pos(parser), "expected ')'");
        }
        parser_step(parser);
        return value;
    } else {
        return parser_operand(parser);
    }
}

Expr* parser_unary(Parser* parser)
{
    if (parser_current_is(parser, TokenTypeMinus)) {
        parser_step(parser);
        return unary_expr(UnaryExprTypeNegate, parser_group(parser));
    } else {
        return parser_group(parser);
    }
}

Expr* parser_multiply_divide(Parser* parser)
{
    Expr* left = parser_unary(parser);
    while (!parser_done(parser)) {
        if (parser_current_is(parser, TokenTypeAsterisk)) {
            parser_step(parser);
            Expr* right = parser_unary(parser);
            left = binary_expr(BinaryExprTypeMultiply, left, right);
        } else if (parser_current_is(parser, TokenTypeSlash)) {
            parser_step(parser);
            Expr* right = parser_unary(parser);
            left = binary_expr(BinaryExprTypeDivide, left, right);
        } else {
            break;
        }
    }
    return left;
}

Expr* parser_add_subtract(Parser* parser)
{
    Expr* left = parser_multiply_divide(parser);
    while (!parser_done(parser)) {
        if (parser_current_is(parser, TokenTypePlus)) {
            parser_step(parser);
            Expr* right = parser_multiply_divide(parser);
            left = binary_expr(BinaryExprTypeAdd, left, right);
        } else if (parser_current_is(parser, TokenTypeMinus)) {
            parser_step(parser);
            Expr* right = parser_multiply_divide(parser);
            left = binary_expr(BinaryExprTypeSubtract, left, right);
        } else {
            break;
        }
    }
    return left;
}

Expr* parser_expr(Parser* parser) { return parser_add_subtract(parser); }

Expr* parse(Lexer* lexer, const char* text, size_t length)
{
    Parser parser = {
        .text = text,
        .length = length,
        .lexer = lexer,
        .current = lexer_next(lexer),
    };
    return parser_expr(&parser);
}

void free_expr(Expr* expr)
{
    switch (expr->type) {
        case ExprTypeError:
            free(expr->error.message);
            break;
        case ExprTypeInt:
            break;
        case ExprTypeUnary:
            free_expr(expr->unary.subject);
            break;
        case ExprTypeBinary:
            free_expr(expr->binary.left);
            free_expr(expr->binary.right);
            break;
        default:
            fprintf(
                stderr,
                "panic: unexhausted value ./%s:%d %s()\n",
                __FILE__,
                __LINE__,
                __func__
            );
            exit(1);
    }
}

const char* unary_expr_type_to_string(UnaryExprType type)
{
    switch (type) {
        case UnaryExprTypeNegate:
            return "Negate";
        default:
            fprintf(
                stderr,
                "panic: unexhausted value ./%s:%d %s()\n",
                __FILE__,
                __LINE__,
                __func__
            );
            exit(1);
    }
}

const char* binary_expr_type_to_string(BinaryExprType type)
{
    switch (type) {
        case BinaryExprTypeAdd:
            return "Add";
        case BinaryExprTypeSubtract:
            return "Subtract";
        case BinaryExprTypeMultiply:
            return "Multiply";
        case BinaryExprTypeDivide:
            return "Divide";
        default:
            fprintf(
                stderr,
                "panic: unexhausted value ./%s:%d %s()\n",
                __FILE__,
                __LINE__,
                __func__
            );
            exit(1);
    }
}

char* expr_to_string(const Expr* expr)
{
    switch (expr->type) {
        case ExprTypeError: {
            char formattet[65536];
            snprintf(
                formattet,
                65536,
                "Error { [%ld] %d:%d \"%s\" }",
                expr->error.pos.index,
                expr->error.pos.line,
                expr->error.pos.col,
                expr->error.message
            );
            return strndup(formattet, 65536);
        }
        case ExprTypeInt: {
            char formattet[65536];
            snprintf(formattet, 65536, "Int(%ld)", expr->int_expr.value);
            return strndup(formattet, 65536);
        }
        case ExprTypeUnary: {
            char* subject = expr_to_string(expr->unary.subject);
            char formattet[65536];
            snprintf(
                formattet,
                65536,
                "Unary { type: %s, subject: %s }",
                unary_expr_type_to_string(expr->unary.type),
                subject
            );
            free(subject);
            return strndup(formattet, 65536);
        }
        case ExprTypeBinary: {
            char* left = expr_to_string(expr->binary.left);
            char* right = expr_to_string(expr->binary.right);
            char formattet[65536];
            snprintf(
                formattet,
                65536,
                "Binary { type: %s, left: %s, right: %s }",
                binary_expr_type_to_string(expr->binary.type),
                left,
                right
            );
            free(left);
            free(right);
            return strndup(formattet, 65536);
        }
        default:
            fprintf(
                stderr,
                "panic: unexhausted value ./%s:%d %s()\n",
                __FILE__,
                __LINE__,
                __func__
            );
            exit(1);
    }
}