#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);
}

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;
        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->length == 1) {
        return boolObject(1);

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

    } else if (s->text[0] == '"') {
        return objFromSlice(s->text, s->length);
    } 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;
    const char *name = first_form->name;

    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, env);
    Object *oldList = arg_forms->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
        const Object tempList = startList(*oldElement);

        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;
}

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)
{
    // printf("eval():\n");
    // printObj(obj);
    switch(obj->type) {
        case TYPE_NUMBER:
        case TYPE_BOOL:
        case TYPE_STRING:
            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
                const 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], env);
                }
                // 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);
                //printEnv(&newEnv);
                deleteEnv(&newEnv);
                return ret;

            } else {
                // printf("Return list as passed");
                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
    };
}

Object catObjects(const Object obj1, const Object obj2, struct Environment *env)
{
    const Object evalObj1 = eval(&obj1, env);
    const Object evalObj2 = eval(&obj2, env);

    char str1[100] = "";
    char str2[100] = "";
    stringObj(str1, &evalObj1);
    stringObj(str2, &evalObj2);
    int length = strlen(str1) + strlen(str2) + 1;

    Object o = newObject(TYPE_STRING);
    o.string = calloc(sizeof(char), length);
    strcat(o.string, str1);
    strcat(o.string, str2);

    return o;
}

Object _basicOp(const Object *obj1, const 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 numberObject(n1 % n2);

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

    return *obj1;
}

Object basicOp(const Object *obj1, const Object *obj2, const char op,
               struct Environment *env)
{
    int lists = (obj1->type == TYPE_LIST) + (obj2->type == TYPE_LIST);
    if(lists == 0) {
        return _basicOp(obj1, obj2, op);
    } else if(lists == 1) { // Single operand is applied to each element in list
        const Object *listObj = (obj1->type == TYPE_LIST)? obj1 : obj2;
        const Object *singleObj = (obj1->type == TYPE_LIST)? obj2 : obj1;
        Object newList = listObject();
        FOR_POINTER_IN_LIST(listObj) {
            Object adding = eval(POINTER, env);
            nf_addToList(&newList, _basicOp(&adding, singleObj, op));
        }
        return newList;
    } else { // 2 lists
        if(listLength(obj1) == listLength(obj2)) {
            Object newList = listObject();
            FOR_POINTERS_IN_LISTS(obj1, obj2) {
                Object ev1 = eval(P1, env);
                Object ev2 = eval(P2, env);
                nf_addToList(&newList, _basicOp(&ev1, &ev2, op));
            }
            return newList;
        } else {
            return errorObject(LISTS_NOT_SAME_SIZE);
        }
    }
}

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

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

#undef bopf

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
    // int statements = 0;
    int i = 0;
    int parens = 0;
    Object obj;
    struct Slice *tok = tokens;
    while(tok[i].text != NULL) {
        //printf("tok[%d].text[0]: '%c'\n", i, tok[i].text[0]);
        if(tok[i].text[0] == '(') {
            parens++;
        } else if(tok[i].text[0] == ')') {
            parens--;
            if(parens == 0) {
                Object parsed = parse(tok).obj;
                tok = &tok[i + 1];
                i = -1;
                obj = eval(&parsed, env);
                //printf("End statement:\n");
                //printObj(&obj);
            }
        }
        i++;
    }
    // for(int i = 0; i < statements; i++) {
    //     Object parsed = parse(tokens).obj;
    // }
    // Object parsed = parse(tokens).obj;
    free(tokens);
    // return eval(&parsed, env);
    return obj;
}

#ifdef STANDALONE
int repl(struct Environment *env)
{
    char input[200] = "";
    while(input[0] != 'q') {
        printf("pebblisp>> ");
        fgets(input, 100, stdin);
        Object obj = parseEval(input, env);
        printAndClean(&obj);
        // printObj(&obj);
        // printEnv(env);
    }
}

int main(int argc, const char* argv[])
{
    struct Environment env = defaultEnv();
    if(argc == 2) {
        Object r = parseEval(argv[1], &env);
        printAndClean(&r);
    } else {
#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