#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

Object evalDefArgs(const Object *argForms, struct Environment *env)
{
    const Object *newSymbol = argForms;
    const char *name = newSymbol->name;

    const Object newValue = eval(newSymbol->forward, env);

    addToEnv(env, name, newValue);

    return *newSymbol;
}

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

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

Object evalMapArgs(const Object *argForms, struct Environment *env)
{
    if(!argForms)
        return errorObject(NULL_MAP_ARGS);
    
    const Object lambda = eval(argForms, env);
    const Object *inputList = argForms->forward;

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

    Object list = listObject();

    FOR_POINTER_IN_LIST(inputList) {
        // Create a new list for each element,
        // since lambda evaluation looks for a list
        Object tempList = startList(cloneObject(*POINTER));

        Object *params = &lambda.lambda->params;
        struct Environment newEnv = envForLambda(params, &tempList, env);

        // Add the lambda evaluation to the list
        nf_addToList(&list, eval(&lambda.lambda->body, &newEnv));
        deleteEnv(&newEnv);
        cleanObject(&tempList);
    }

    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
        Object *ptr = itemAt(src, i + 1); // Skip the first
        destList[i] = eval(ptr, env);
    }
}

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

        case TYPE_STRING:
            return copyString(*obj);

        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 builtIn =
                        evalBuiltIns(first_form, first_form->forward, env);
                
                if(builtIn.type != TYPE_ERROR) {
                    return builtIn;
                }
            }

            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++) {
                    Object toClean = func_eval;
                    func_eval = first_eval.func(func_eval, rest[i], env);
                    //if(i != length - 1)
                        cleanObject(&toClean);
                    cleanObject(&rest[i]);
                }

                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 {
                Object list = listObject();
                FOR_POINTER_IN_LIST(obj) {
                    nf_addToList(&list, eval(POINTER, env));
                }
                return list;
            }
        }
        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)
{
    Object evalObj1 = eval(&obj1, env);
    Object evalObj2 = eval(&obj2, env);

    char str1[100] = "";
    char str2[100] = "";
    stringObj(str1, &evalObj1);
    stringObj(str2, &evalObj2);
    cleanObject(&evalObj1);
    cleanObject(&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,
                struct Environment *env)
{
    const int n1 = obj1->number;
    const int n2 = obj2->number;

    switch(op){
        case '+':
            if(obj1->type == TYPE_STRING || obj2->type == TYPE_STRING)
                return catObjects(*obj1, *obj2, env);
            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, env);

    } 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, env));
        }
        return newList;

    } else { // 2 lists with the op applied to matching indices of both lists
        if(listLength(obj1) == listLength(obj2)) {
            Object newList = listObject();
            FOR_POINTERS_IN_LISTS(obj1, obj2) {
                const Object ev1 = eval(P1, env);
                const Object ev2 = eval(P2, env);
                nf_addToList(&newList, _basicOp(&ev1, &ev2, op, env));
            }
            return newList;
        } else {
            return errorObject(LISTS_NOT_SAME_SIZE);
        }
    }
}

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

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

#undef BASIC_OP

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)
{
    if(!s) {
        printf("NULL SLICE\n");
        return;
    }
    printf("Debug Slice\n    text:'");
    for(int i = 0; i < s->length; i++) {
        printf("%c", s->text[i]);
        if(s->text[i] == '\0')
            printf("NULLCHAR\n");
    }
    printf("'\n");
    printf("  length: %d\n", s->length);
}

Result parse(struct Slice *slices)
{
    struct Slice *token = slices;
    if(token && token->text) {
        struct Slice *rest = &slices[1];
        if(token->text[0] == '(') {
            // todo check for null rest
            return readSeq(rest);
        } else { // todo error on missing close paren
            return result(parseAtom(token), rest);
        }
    } else {
        return result(errorObject(NULL_PARSE), NULL);
    }
}

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

Object parseAtom(struct Slice *s)
{
    if(isDigit(s->text[0])) {
        if(s->text[0] != '0' || s->length == 1)
            return parseDecimal(s);
        else {
            return errorObject(UNSUPPORTED_NUMBER_TYPE);
        }

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

    } else if (s->length == 1 && (s->text[0] == 'F' || s->text[0] == 'f')) {
        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 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 i = 0;
    int parens = 0;
    Object obj = numberObject(0);
    struct Slice *tok = tokens;
    if(tok[i].text[0] != '(') {
        Object parsed = parse(tok).obj;
        obj = eval(&parsed, env);
        cleanObject(&parsed);
    } else {
        while(tok[i].text != NULL) {
            if(tok[i].text[0] == '(') {
                parens++;
            } else if(tok[i].text[0] == ')') {
                parens--;
                if(parens == 0) {
                    cleanObject(&obj);
                    Object parsed = parse(tok).obj;
                    tok = &tok[i + 1];
                    i = -1;
                    obj = eval(&parsed, env);
                    cleanObject(&parsed);
                }
            }
            i++;
        }
    }
    free(tokens);
    return obj;
}

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

int main(int argc, const char* argv[])
{
    struct Environment env = defaultEnv();
    if(argc >= 2) {
        Object r = numberObject(0);
        for(int i = 1; i < argc; i++) {
            r = parseEval(argv[i], &env);
            printAndClean(&r);
        }
    } else {
        repl(&env);
    }
    deleteEnv(&env);
}
#endif