#include <stdlib.h>
#include "syntax.h"
#include "utils.h"


int parse_num(char* str) {
    // TODO: switch to dedicated Result type later
    // TODO: add other bases (per bash arithmetic syntax)
    char* endptr;
    long n = strtol(str, &endptr, 10);
    if (*endptr == '\0') {
        return (int)n;
    } else {
        exit(42);
    }
}


int eval_binop(BinOp op, int left, int right) {
    switch (op) {
        case PLUS:
            return left+right;
        case MULT:
            return left*right;
        default:
            exit(99);
    }
}

int eval_arithm_node(ArithmNode node, ShellState* shstate) {
    char* num_str;
    int left_val, right_val;

    switch (node.kind) {
        case ARITHM_INT_LIT:
            return node.as.lit_val;
        case ARITHM_VAR:
            num_str = get_var(node.as.varname, shstate);
            return parse_num(num_str);
        case ARITHM_BINOP:
            left_val = eval_arithm_node(*node.as.binop.left, shstate);
            right_val = eval_arithm_node(*node.as.binop.right, shstate);
            return eval_binop(node.as.binop.op, left_val, right_val); 
    }
}


int eval_arithm_ast(ArithmAst ast, ShellState* shstate) {
    // TODO: clean up the tree
    return eval_arithm_node(*ast.root, shstate);
}