pebblisp/src/env.c

#include "env.h"

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

#include "pebblisp.h"

Object fetchFromEnvironment(const char* name, struct Environment* env)
{
    if (!env) {
        return errorObject(NULL_ENV);
    }

    if (env->size == 0) {
        if (env->outer) {
            return fetchFromEnvironment(name, env->outer);
        } else {
            return errorObject(EMPTY_ENV);
        }
    }

    for (int i = 0; i < env->size; i++) {
        if (env->strings[i] == NULL) {
            printd("Try %d (NULL)\n", i);
            break;
        }

        printd("Try %d (%s)\n", i, env->strings[i]);
        debugObj(&env->objects[i]);
        if (strcmp(name, env->strings[i]) == 0) {
            printd("Returning!\n");
            return cloneObject(env->objects[i]);
        }
    }

    printd("Trying outer %p\n", env->outer);
    if (env->outer) {
        return fetchFromEnvironment(name, env->outer);
    }

    return errorWithContext(DID_NOT_FIND_SYMBOL, name);
}

struct Environment envForLambda(const Object* params, const Object* arg_forms,
                                struct Environment* outer)
{
    int paramCount = listLength(params);

    struct Environment env = {.outer = outer,
        .strings = NULL,
        .objects = NULL,
        .structCount = 0,
        .size = paramCount};

    if (paramCount == 0) {
        return env;
    }

    env.strings = calloc(sizeof(char*), paramCount + 1);
    env.objects = malloc(sizeof(Object) * (paramCount + 1));

    const Object* march = arg_forms;
    for (int i = 0; i < paramCount; i++) {
        const char* newObjName = itemAt(params, i)->string;
        // Eval the `march` list
        Object newEnvObj = eval(march, outer);
        addToEnv(&env, newObjName, newEnvObj);    // Could use eval_forms?
        cleanObject(&newEnvObj);
        march = march->forward;
    }

    return env;
}

// Determine if a given symbol exists in the given environment chain
//
// Modifies `env` to the environment that the symbol was found in, only if the
// symbol was found
//
// Returns the index of the symbol in the environment, if found. Otherwise, -1
int findInEnv(struct Environment** env, const char* name)
{
    struct Environment* temp_env = *env;
    while (temp_env) {
        for (int i = 0; i < temp_env->size; i++) {
            if (temp_env->strings[i] == NULL) {
                break;
            }
            if (strcmp(temp_env->strings[i], name) == 0) {
                *env = temp_env;
                return i;
            }
        }
        temp_env = temp_env->outer;
    }
    return -1;
}

// TODO Maybe extend environment using a new outer, instead of realloc
void addToEnv(struct Environment* env, const char* name, const Object obj)
{
    // int sym_pos = findInEnv(&env, name);
    // if(sym_pos != -1) {
    //     Object o = cloneObject(obj);
    //     cleanObject(&env->objects[sym_pos]);
    //     env->objects[sym_pos] = o;
    //     return;
    // }

    int i;
    struct Environment* temp_env = env;
    int is_local = 1;
    while (temp_env) {
        for (i = 0; i < temp_env->size; i++) {
            // Add *new* item to env only if we're in the local scope
            if (temp_env->strings[i] == NULL) {
                if (is_local) {
                    temp_env->strings[i] =
                        calloc(sizeof(char), strlen(name) + 1);
                    strncpy(temp_env->strings[i], name, strlen(name));
                    temp_env->objects[i] = cloneObject(obj);
                    return;
                }
                break;
            } else if (strcmp(temp_env->strings[i], name) == 0) {
                Object o = cloneObject(obj);
                cleanObject(&temp_env->objects[i]);
                temp_env->objects[i] = o;
                return;
            }
        }
        temp_env = temp_env->outer;
        is_local = 0;
    }

    printd("Reallocating environment\n");
    const int inc = 5;
    const int old_size = env->size;
    env->size += inc;
    env->strings = realloc(env->strings, sizeof(char*) * env->size);
    env->objects = realloc(env->objects, sizeof(Object) * env->size);

    for (int j = 0; j < inc; j++) {
        env->strings[old_size + j] = NULL;
    }

    env->strings[old_size] = malloc(strlen(name) + 1);
    strncpy(env->strings[old_size], name, strlen(name) + 1);
    env->objects[old_size] = cloneObject(obj);
}

void printEnv(struct Environment* env)
{
    if (!env) {
        printf("NULL env\n");
        return;
    }
    for (int i = 0; i < env->size; i++) {
        if (env->strings[i] == NULL) {
            printf("env[%d]: NULL %p\n", i, env->strings[i]);
            break;
        }
        printf("env[%d]: '%s' %p\n", i, env->strings[i], env->strings[i]);
        printf("  ");
        printObj(&env->objects[i]);
        printf("");
    }
}

void addFunc(const char* name,
             Object (* func)(Object, Object, struct Environment*),
             struct Environment* env)
{
    Object o = newObject(TYPE_FUNC);
    o.func = func;
    addToEnv(env, name, o);
}

void deleteEnv(struct Environment* e)
{
    if (e->strings) {
        int i = 0;
        while (e->strings[i]) {
            free(e->strings[i]);
            cleanObject(&e->objects[i]);
            i++;
        }
        free(e->strings);
        e->strings = NULL;

        free(e->objects);
        e->objects = NULL;
    }
}

struct symFunc {
    const char* sym;

    Object (* func)(Object, Object, struct Environment*);
};

struct Environment defaultEnv()
{
    char** strings = calloc(sizeof(char*), MAX_ENV_ELM);
    Object* objects = malloc(sizeof(Object) * MAX_ENV_ELM);
    char size = MAX_ENV_ELM;

    struct Environment e = {
        .outer = NULL,
        .strings = strings,
        .objects = objects,
        .size = size,
        .structCount = 0,
    };

    struct symFunc symFuncs[] = {
        {"+", &add},
        {"-", &sub},
        {"*", &mul},
        {"/", &dvi},
        {"%", &mod},
        {"=", &equ},
        {">", &gth},
        {"<", &lth},
        {"&", &and},
        {"|", &or},
        {"cat", &catObjects},
        {"fil", &filter},
        {"len", &len},
        {"ap", &append},
        {"pre", &prepend},
        {"at", &at},
        {"rest", &rest},
        {"chat", &charAt},
#ifndef LOW_MEM
        {"rev", &reverse},
#endif
        {"isnum", &isNum},
        {"isstr", &isString},
        {"iserr", &isErr},
        {"char", &charVal},
        {"eval", &parseEvalO},
#ifdef STANDALONE
        {"prn", &print},
        {"pch", &pChar},
        {"penv", &printEnvO},
        //{"sys", &systemCall},
        {"loadfile", &loadFile},
        {"inp", &takeInput},
#endif
    };

    for (unsigned i = 0; i < sizeof(symFuncs) / sizeof(symFuncs[0]); i++) {
        addFunc(symFuncs[i].sym, symFuncs[i].func, &e);
    }

    return e;
}