#include <assert.h>
#include <inttypes.h>
#include <stdio.h>

#include "eval.h"

static int evaluate_value(const struct Node* node, int64_t* out);

static int complain(const struct Node* node, const char* message)
{
    (void)fprintf(stderr, "line %d: %s\n", node->line, message);
    return 1;
}

static int evaluate_operands(const struct Node* node, int64_t* left, int64_t* right)
{
    if (evaluate_value(node->first, left))
        return 1;

    return evaluate_value(node->second, right);
}

static int evaluate_value(const struct Node* node, int64_t* out)
{
    int64_t left = 0;
    int64_t right = 0;
    switch (node->kind)
    {
        case VALUE_DIFFERENCE:
            *out = (int64_t)node->first->character - (int64_t)node->second->character;
            return 0;
        case VALUE_SUM:
            if (evaluate_operands(node, &left, &right))
                return 1;

            *out = left + right;
            return 0;
        case VALUE_PRODUCT:
            if (evaluate_operands(node, &left, &right))
                return 1;

            *out = left * right;
            return 0;
        case VALUE_QUOTIENT:
            if (evaluate_operands(node, &left, &right))
                return 1;

            if (right == 0)
                return complain(node, "division by zero");

            *out = left / right;
            return 0;
        default: break;
    }

    assert(!"the parser handed a non-value where a value goes");
    return 1;
}

static int evaluate_type(const struct Node* node, struct Type* out)
{
    out->kind = KIND_VOID;
    out->number = 0;
    switch (node->kind)
    {
        case TYPE_DECLTYPE:
            if (evaluate_value(node->first, &out->number))
                return 1;
            out->kind = KIND_VALUE;
            return 0;
        default: break;
    }

    assert(!"the parser handed a non-type where a type goes");
    return 1;
}

static enum RunStatus emit(const struct Node* node)
{
    struct Type type;
    if (evaluate_type(node->first, &type))
        return RUN_FAILED;

    if (type.kind == KIND_VALUE)
        (void)printf("%" PRId64 "\n", type.number);
    return RUN_DONE;
}

static enum RunStatus execute_one(const struct Node* node)
{
    switch (node->kind)
    {
        case STMT_EMIT: return emit(node);
        default: break;
    }

    assert(!"the parser handed a non-statement where a statement goes");
    return RUN_FAILED;
}

enum RunStatus execute(const struct Node* statement)
{
    while (statement != NULL)
    {
        enum RunStatus status = execute_one(statement);
        if (status != RUN_DONE)
            return status;

        statement = statement->next;
    }

    return RUN_DONE;
}