#include "calc.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static inline bool isBinaryOp(TokenType tt);
static inline ExprType binaryOpExprType(TokenType tt);
static inline bool contains(char ch, const char* string);

static inline int evalText(const char* text);

int main(void)
{
    while (true) {
        printf("> ");
        fflush(stdout);
        char line[128] = "";
        fgets(line, 127, stdin);
        size_t line_length = strlen(line);
        line[--line_length] = '\0';
        printf("line = \"%s\"\n", line);
        int result = evalText(line);
        printf("%d\n", result);
    }

    Expr* expr = binaryExprNew(ET_Add, intExprNew(-200), intExprNew(23));
    exprPrint(expr);
    fputc('\n', stdout);
    int result = exprEval(expr);
    printf("%d\n", result);
    exprFree(expr);
}

static inline int evalText(const char* text)
{
    Token tokens[128];
    size_t tokens_size = lex(tokens, 128, text);

    Parser parser;
    parserConstruct(&parser, tokens, tokens_size);

    Expr* expr = parseExpr(&parser);
    if (!expr)
        return 0;

    int result = exprEval(expr);
    exprFree(expr);

    return result;
}

void parserConstruct(Parser* parser, Token* tokens, size_t tokens_size)
{
    *parser = (Parser) {
        .tokens = tokens,
        .tokens_size = tokens_size,
        .i = 0,
    };
}

void parserStep(Parser* parser)
{
    parser->i += 1;
}

bool parserDone(const Parser* parser)
{
    return parser->i >= parser->tokens_size;
}

Token parserCurrent(const Parser* parser)
{
    return parser->tokens[parser->i];
}

Expr* parseExpr(Parser* parser)
{
    if (parserDone(parser)) {
        fprintf(stderr, "error: expected expr, got end-of-file\n");
        return NULL;
    }

    Token tok = parserCurrent(parser);
    if (isBinaryOp(tok.type)) {
        parserStep(parser);
        Expr* left = parseExpr(parser);
        if (!left)
            return NULL;
        Expr* right = parseExpr(parser);
        if (!right)
            return NULL;
        ExprType et = binaryOpExprType(tok.type);
        return binaryExprNew(et, left, right);
    } else if (tok.type == TT_Int) {
        parserStep(parser);
        return intExprNew(tok.value);
    } else {
        parserStep(parser);
        fprintf(stderr, "error: expected expr\n");
        return NULL;
    }
}

size_t lex(Token* tokens, size_t tokens_max_size, const char* text)
{
    const size_t text_length = strlen(text);

    size_t tokens_i = 0;
    size_t i = 0;
    while (i < text_length && tokens_i < tokens_max_size) {

        while (contains(text[i], " \t\n")) {
            i++;
        }
        if (contains(text[i], "1234567890")) {
            char text_value[16] = "";
            size_t j = 0;
            while (contains(text[i], "1234567890") && j < 15) {
                text_value[j] = text[i];
                j++;
                i++;
            }
            tokens[tokens_i++]
                = (Token) { .type = TT_Int, .value = atoi(text_value) };
        } else if (contains(text[i], "+-*/")) {
            char ch = text[i];
            i++;
            tokens[tokens_i++] = (Token) {
                .type = (TokenType)ch,
                .value = 0,
            };
        } else {
            char ch = text[i];
            i++;
            fprintf(stderr, "error: illegal character '%c'\n", ch);
        }
    }

    return tokens_i;
}

static inline bool isBinaryOp(TokenType tt)
{
    switch (tt) {
        case TT_Plus:
        case TT_Minus:
        case TT_Asterisk:
        case TT_Slash:
            return true;
        case TT_Int:
        default:
            return false;
    }
}

static inline ExprType binaryOpExprType(TokenType tt)
{

    switch (tt) {
        case TT_Plus:
            return ET_Add;
        case TT_Minus:
            return ET_Subtract;
        case TT_Asterisk:
            return ET_Multiply;
        case TT_Slash:
            return ET_Divide;
        case TT_Int:
            break;
    }
    return 0;
}

static inline bool contains(char ch, const char* string)
{
    for (size_t i = 0; i < strlen(string); ++i) {
        if (string[i] == ch) {
            return true;
        }
    }
    return false;
}