#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "env.h"
#include "primitives.h"

datum* define_variable(const char *var, datum *value, environment *env) {
    if (env->first_mapping == NULL) {
        env->first_mapping = new_mapping(var, value);
        return NULL;
    }

    mapping* m = env->first_mapping;
    while (1) {
        if (strcmp(var, m->variable) == 0) {
            m->value = value;
        }
        if (m->next) {
            m = m->next;
        } else {
            break;
        }
    }

    m->next = new_mapping(var, value);
    return NULL;
}

datum* lookup_variable_value(char* var, environment* env) {
    environment* e = env;
    mapping* m;

    while (e) {
        m = e->first_mapping;
        while (m) {
            if (strcmp(var, m->variable) == 0) {
                return m->value;
            }
            m = m->next;
        }
        e = e->outer_env;
    }

    printf("UNDEFINED VARIABLE %s", var);
    exit(-1);
}

datum* make_compiled_proc(void* entry, environment* e) {
    datum* r = malloc(sizeof(datum));
    if (!r) exit(-1);
    r->type = datum_type_compiled_proc;
    r->compiled_procedure_entry = entry;
    r->env = e;
    return r;
}

environment* extend_environment(const char **args, datum *argl, environment* outer_env) {
    environment* env = malloc(sizeof(environment));
    if (!env) exit(-1);
    env->first_mapping = NULL;
    env->outer_env = outer_env;

    size_t i = 0;
    while (argl && args[i]) {
        define_variable(args[i], argl, env);
        i += 1;
        argl = argl->next;
    }

    return env;
}

environment* get_global_environment(void) {
    environment* env = malloc(sizeof(environment));
    if (!env) exit(-1);
    env->first_mapping = NULL;
    env->outer_env = NULL;
    define_variable("+", const_primitive_proc(&add), env);
    define_variable("-", const_primitive_proc(&sub), env);
    define_variable("*", const_primitive_proc(&mul), env);
    define_variable("=", const_primitive_proc(&eq), env);
    define_variable("<", const_primitive_proc(&lt), env);
    define_variable("display", const_primitive_proc(&display), env);
    define_variable("newline", const_primitive_proc(&newline), env);
    return env;
}

mapping* new_mapping(const char* var, datum* value) {
    mapping* m = malloc(sizeof(mapping));
    if (!m) exit(-1);
    m->variable = var;
    m->value = value;
    m->next = NULL;
    return m;
}