#include "pebblisp.h"
#include "tokens.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#ifndef STANDALONE
#undef printf
#define printf(...) APP_LOG(APP_LOG_LEVEL_DEBUG, __VA_ARGS__)
#endif

void copySlice(char * dest, struct Slice *src)
{
    if(!dest || !src)
        return;
    strncpy(dest, src->text, src->length);
    dest[(int)src->length] = '\0';
}

void debugSlice(struct Slice *s)
{
    printd("Debug Slice\n    text:'");
    for(int i = 0; i < s->length; i++) {
        printd("%c", s->text[i]);
        if(s->text[i] == '\0')
            printd("NULLCHAR\n");
    }
    printd("'\n");
    printd("  length: %d\n", s->length);
}

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

    printd("Fetching '%s' from env\n", name);
    printEnv(env);
    for(int i = 0; i < env->size; i++) {
        if(strcmp(name, env->strings[i]) == 0) {
            return env->objects[i];
        }
    }

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

    return errorObject(DID_NOT_FIND_SYMBOL);
}

Result parse(struct Slice *slices)
{
    struct Slice *token = slices;
    struct Slice *rest;
    if(token->text != NULL) {
        rest = &slices[1];
    } else {
        return result(errorObject(NULL_PARSE), NULL);
    }

    if(token->text[0] == '(') {
        // todo check for null rest
        return readSeq(rest);
    } else { // todo error on missing close paren
        return result(parseAtom(token), rest);
    }
}

Result readSeq(struct Slice *tokens)
{
    Object res = listObject();
    for(;;) {
        struct Slice *next = &tokens[0];
        struct Slice *rest = next->text? &next[1] : NULL;
        if(next->text[0] == ')') {
            return result(res, rest);
        }
        Result r = parse(tokens);
        nf_addToList(&res, r.obj);
        tokens = r.slices;
    }
}

Object parseAtom(struct Slice *s)
{
    if(isDigit(s->text[0])) {
        int num = 0;
        for(int i = 0; i < s->length; i++) {
            num *= 10;
            num += s->text[i] - '0';
        }
        return numberObject(num);

    } else if (s->text[0] == 'T' && s->text[1] == '\0') {
        return boolObject(1);

    } else if (s->text[0] == 'F' && s->text[1] == '\0') {
        return boolObject(0);

    } else {
        Object o = symbolObject();
        copySlice(o.name, s);
        return o;
    }
}

Object evalDefArgs(const Object *arg_forms, struct Environment *env)
{
    const Object *first_form = &arg_forms[0];
    const char *name = first_form->name;

    // Immediately adding the function to the env might allow recursion?
    Object second_eval = eval(first_form->forward, env);

    addToEnv(env, name, second_eval);

    return *first_form;
}

Object evalIfArgs(const Object *arg_forms, struct Environment *env)
{
    return eval(arg_forms, env).number? 
            eval(arg_forms->forward, env) : 
            eval(arg_forms->forward->forward, env);
}

Object evalLambdaArgs(const Object *arg_forms)
{
                         // params               // body
    return constructLambda(arg_forms, arg_forms? arg_forms->forward : NULL);
}

Object evalMapArgs(const Object *arg_forms, struct Environment *env)
{
    if(!arg_forms)
        return errorObject(NULL_MAP_ARGS);
    
    const Object lambda = eval(&arg_forms[0], env);
    Object *oldList = (&arg_forms[0])->forward;

    if(lambda.type != TYPE_LAMBDA || oldList->type != TYPE_LIST)
        return errorObject(BAD_TYPE);

    Object list = listObject();

    const Object *oldElement = oldList->list;
    while(oldElement != NULL) {
        // Create a new list for each element in the list,
        // since lambda evaluation looks for a list
        Object tempList = listObject();
        Object listBack[1] = {*oldElement};
        listBack[0].forward = NULL;
        tempList.list = listBack;

        struct Environment newEnv = 
                envForLambda(&lambda.lambda->params, &tempList, env);
        const Object evalLambda = eval(&lambda.lambda->body, &newEnv);

        nf_addToList(&list, evalLambda);
        oldElement = oldElement->forward;
    }

    return list;
}

struct Environment envForLambda(const Object *params, const Object *arg_forms,
                                struct Environment *outer)
{
    printd("envForLambda()\n");
    debugObj(arg_forms);

    int length = listLength(params);

    struct Environment env;
    env.outer = outer;
    env.strings = NULL;
    env.objects = NULL;
    env.size = length;

    if(length == 0)
        return env;

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

    Object vs[length];
    eval_forms(vs, arg_forms, outer);

    for(int i = 0; i < length; i++) {
        const char *n = itemAt(params, i)->name;
        addToEnv(&env, n, eval(&arg_forms[i], outer)); // May not need eval?
            // SHOULD BE `vs` not arg_forms???
    } // Something is segfaulting, anyway
    // env.strings[length] = NULL;

    return env;
}

Object evalBuiltIns(const Object *first, const Object *rest,
                    struct Environment *env)
{
    if(strcmp(first->name, "def") == 0) {
        return evalDefArgs(rest, env);
    } else if(strcmp(first->name, "if") == 0) {
        return evalIfArgs(rest, env);
    } else if(strcmp(first->name, "fn") == 0) {
        return evalLambdaArgs(rest);
    } else if(strcmp(first->name, "map") == 0) {
        return evalMapArgs(rest, env);
    }

    return errorObject(BUILT_IN_NOT_FOUND);
}

void eval_forms(Object *destList, const Object *src, struct Environment *env)
{
    int length = listLength(src) - 1; // Not counting first_form
    for(int i = 0; i < length; i++) { // Evaluates all in list
        destList[i] = eval(itemAt(src, i + 1), env); // Skip the first
    }
}

Object eval(const Object *obj, struct Environment *env)
{
    printd("eval():\n");
    debugObj(obj);
    switch(obj->type) {
        case TYPE_NUMBER:
        case TYPE_BOOL:
            return *obj; // Return as is

        case TYPE_SYMBOL:
            return fetchFromEnvironment(obj->name, env);

        case TYPE_LIST:
        {
            if(listLength(obj) == 0)
                return *obj;

            if(listLength(obj) == 1)
                return eval(obj->list, env);

            Object *first_form = obj->list;

            { // Try to eval built-ins
                Object built_in = 
                        evalBuiltIns(first_form, first_form->forward, env);
                
                // deleteList(obj); // Decreases indirectly lost memory, but fails on Pebble
                if(built_in.type != TYPE_ERROR) {
                    return built_in;
                }
            }

            Object first_eval = eval(first_form, env);
            if(first_eval.type == TYPE_FUNC) {
                int length = listLength(obj) - 1; // Not counting first_form
                Object rest[length];
                eval_forms(rest, obj, env);

                Object func_eval = rest[0];
                for(int i = 1; i < length; i++) {
                    func_eval = first_eval.func(func_eval, rest[i]);
                }
                // deleteList(obj); // Decreases indirectly lost memory, but fails on Pebble
                return func_eval;

            } else if (first_eval.type == TYPE_LAMBDA) {
                struct Environment newEnv = 
                        envForLambda(&first_eval.lambda->params, first_form->forward, env);
                Object ret = eval(&first_eval.lambda->body, &newEnv);
                deleteEnv(&newEnv);
                return ret;

            } else {
                return *obj;
            }
        }
        case TYPE_LAMBDA:
            return errorObject(UNEXPECTED_FORM);

        default:
        ;
    }
    return *obj;
}

Result result(Object obj, struct Slice *slices)
{
    return (Result) {
        .obj = obj,
        .slices = slices
    };
}

// todo could include and return a starting index for faster multi-adds
// Maybe extend existing environment using a malloc'd outer, instead of realloc
void addToEnv(struct Environment *env, const char *name, const Object obj)
{
    int i;
    for(i = 0; i < env->size ; i++) {
        if(env->strings[i] == NULL) {
            env->strings[i] = calloc(sizeof(char), strlen(name) + 1);
            strncpy(env->strings[i], name, strlen(name));
            env->objects[i] = obj;
            return;
        }
        if(strcmp(env->strings[i], name) == 0) {
            cleanObject(&env->objects[i]);
            env->objects[i] = obj;
            return;
        }
    }

    printd("Reallocating environment\n");
    const int inc = 5;
    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[i + j] = NULL;
    }

    env->strings[i] = malloc(strlen(name) + 1);
    strncpy(env->strings[i], name, strlen(name) + 1);
    env->objects[i] = 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)
            return;
        printd("env[%d]: '%s'\n  ", i, env->strings[i]);
        debugObj(&env->objects[i]);
    }
}

Object basicOp(Object *obj1, Object *obj2, const char op)
{
    const int n1 = obj1->number;
    const int n2 = obj2->number;

    switch(op){
        case '+':
            return numberObject(n1 + n2);
        case '-':
            return numberObject(n1 - n2);
        case '*':
            return numberObject(n1 * n2);
        case '/':
            return numberObject(n1 / n2);

        case '=':
            return boolObject(n1 == n2);
        case '>':
            return boolObject(n1 > n2);
        case '<':
            return boolObject(n1 < n2);
    }

    return *obj1;
}

#define bopf(_name, _char) \
Object _name(Object obj1, Object obj2) \
    { return basicOp(&obj1, &obj2, _char); }

bopf(add, '+');
bopf(sub, '-');
bopf(mul, '*');
bopf(dvi, '/');
bopf(equ, '=');
bopf(gth, '>');
bopf(lth, '<');

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

void deleteEnv(struct Environment *e)
{
    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 Environment defaultEnv() {
    struct Environment e;
    e.outer = NULL;
    e.strings = calloc(sizeof(char*), MAX_ENV_ELM);
    e.size = MAX_ENV_ELM;
    // for(int i = 0; i < MAX_ENV_ELM; i++) {
    //     e.strings[i] = NULL;
    // }

    e.objects = malloc(sizeof(Object) * MAX_ENV_ELM);

    addFunc("+", &add, &e);
    addFunc("-", &sub, &e);
    addFunc("*", &mul, &e);
    addFunc("/", &dvi, &e);
    addFunc("=", &equ, &e);
    addFunc(">", &gth, &e);
    addFunc("<", &lth, &e);

    return e;
}

Object parseEval(const char *input, struct Environment *env)
{
    struct Slice *tokens = nf_tokenize(input);
    if(!tokens)
        return errorObject(MISMATCHED_PARENS);
#ifdef DEBUG
    struct Slice *debug = tokens;
    if(debug) {
        while(debug->text) {
            char tok[MAX_TOK_LEN];
            copySlice(tok, debug);
            //printd("slice: '%s'\n", tok);
            debug++;
        }
    }
#endif
    Object parsed = parse(tokens).obj;
    free(tokens);
    Object ret = eval(&parsed, env);
    cleanObject(&parsed);
    return ret;
}

#ifdef STANDALONE
int repl(struct Environment *env)
{
    char input[100] = "";
    while(input[0] != 'q') {
        printf("pebblisp>> ");
        fgets(input, 100, stdin);
        Object obj = parseEval(input, env);
        // printAndClean(&obj);
        printObj(&obj);
        // printEnv(env);
    }
}

int main(void)
{
    struct Environment env = defaultEnv();
#ifndef NO_REPL
    repl(&env);
#else
    Object r = parseEval("(def ad (fn (a) (+ 1 a)))", &env);
    printAndClean(&r);
    r = parseEval("(map ad (1 2 3))", &env);
    //printAndClean(&r);
#endif
    deleteEnv(&env);
}
#endif