#include "environment.h"
#include "gc.h"
#include "errors.h"

Environment *
env_create(Environment *parent) {
    Environment *env = alloc_env();
    env->parent = parent;
    env->marked = false;
    env->entries = NULL;
    array_init(env->entries, ENV_BUF_CAP);
    return env;
}

void
env_add_symbol(Environment *env, Object *symbol, Object *value) {
    if (symbol->type != OBJ_TYPE_SYMBOL) {
        error_push((Error){
            .type = ERR_TYPE_RUNTIME,
            .value = ERR_NOT_A_SYMBOL,
            .line = 0,
            .col = 0,
        });
        return;
    }
    EnvEntry entry = (EnvEntry){symbol, value};
    array_push(env->entries, entry);
}

Object *
env_lookup(Environment *env, Object *symbol) {
    while (env != NULL) {
        for (size_t i = 0; i < array_size(env->entries); i++) {
            EnvEntry entry = env->entries[i];
            if (obj_eq(symbol, entry.symbol)) {
                return entry.value;
            }
        }
        env = env->parent;
    }
    return obj_err;
}

Object *
env_update(Environment *env, Object *symbol, Object *value) {
    while (env != NULL) {
        for (size_t i = 0; i < array_size(env->entries); i++) {
            EnvEntry entry = env->entries[i];
            if (obj_eq(symbol, entry.symbol)) {
                env->entries[i].value = value;
                return obj_nil;
            }
        }
        env = env->parent;
    }
    error_push((Error){
        .type = ERR_TYPE_RUNTIME,
        .value = ERR_SYMBOL_NOT_FOUND,
    });
    return obj_err;
}

ssize_t
env_index_current(Environment *env, Object *symbol) {
    for (size_t i = 0; i < array_size(env->entries); i++) {
        EnvEntry entry = env->entries[i];
        if (obj_eq(symbol, entry.symbol)) {
            return i;
        }
    }
    return -1;
}

void
env_add_or_update_current(Environment *env, Object *symbol, Object *value) {
    ssize_t index = env_index_current(env, symbol);
    if (index == -1) {
        env_add_symbol(env, symbol, value);
    } else {
        env->entries[index].value = value;
    }
}

Environment *
env_extend(Environment *parent, Environment *extra) {
    Environment *env = parent;
    for (size_t i = 0; i < array_size(extra->entries); i++) {
        EnvEntry entry = extra->entries[i];
        Environment *tmp = env;
        bool found = false;
        while (tmp != NULL) {
            if (env_index_current(tmp, entry.symbol) != -1) {
                found = true;
                break;
            }
            tmp = tmp->parent;
        }
        if (!found) {
            env_add_symbol(env, entry.symbol, entry.value);
        }
    }
    return env;
}