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

#ifndef STANDALONE
#define printf(...) copySlice(NULL, NULL)
#else
#endif

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

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

Object fetchFromEnvironment(const char *name, struct Environment *env)
{
    int i = 0;
    const char *next = env->strings[i];
    while(next != NULL) {
        // printf("fetching '%s' against '%s'\n", name, next);
        if(strcmp(name, next) == 0) {
            return env->objects[i];
        }
        next = env->strings[++i];
    }
    printf("DID NOT FIND SYMBOL\n");
    Object o;
    o.type = TYPE_ERROR;
    return o;
}

Result parse(struct Slice *slices)
{
    // printf("parse()\n");
    struct Slice *token = slices;
    struct Slice *rest;
    if(token->text != NULL) {
        rest = &slices[1];
    } else {
        // printf("Assigning null...\n");
        rest = NULL;
    }

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

Result readSeq(struct Slice *tokens)
{
    // printf("readSeq()\n");
    Object res;
    res.forward = NULL;
    res.type = TYPE_LIST;
    //res.list = malloc(sizeof(Object));

    Object *march = &res;
    for(;;) {
        struct Slice *next = &tokens[0];
        struct Slice *rest = next->text? &next[1] : NULL;
        if(next->text[0] == ')') {
            return R(res, rest);
        }
        Result r = parse(tokens);
        march->forward = malloc(sizeof(Object));
        *march->forward = r.obj;
        // char out[MAX_TOK_LEN];
        // printf("stringObj: %s\n", stringObj(out, &r.obj));
        tokens = r.slices;
        march = march->forward;
    }
}

Object parseAtom(struct Slice *s)
{
    // printf("parseAtom()\n");
    Object o;
    o.forward = NULL;
    if(isDigit(s->text[0])) {
        o.type = TYPE_NUMBER;
        o.number = 0;
        for(int i = 0; i < s->length; i++) {
            o.number *= 10;
            o.number += s->text[i] - '0';
        }

    } else {
        o.type = TYPE_SYMBOL;
        copySlice(o.name, s);
    }
    return o;
}

Object eval(Object *obj, struct Environment *env)
{
    Object o = *obj;
    switch(obj->type) {
        case TYPE_NUMBER:
        {
            return *obj;
        }
        case TYPE_LIST:
        {
            // printf("TYPE_LIST\n");
            Object first_form = *obj->forward;
            Object first_eval = eval(&first_form, env);
            return first_eval.func(*first_form.forward, *first_form.forward->forward);
        }
        case TYPE_SYMBOL:
        {
            return fetchFromEnvironment(obj->name, env);
        }
        default:
        ;
    }
    return o;
}

char* stringObj(char *dest, Object *obj)
{
    if(obj->type == TYPE_NUMBER) {
        snprintf(dest, MAX_TOK_LEN, "%d", obj->number);
    } else if(obj->type == TYPE_SYMBOL) {
        return obj->name;
    }

    return dest;
}

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

Object basicOp(Object *obj1, Object *obj2, const char op)
{
    Object o;
    o.forward = NULL;
    o.type = TYPE_NUMBER;
    switch(op){
        case '+':
            o.number = obj1->number + obj2->number;
            break;
        case '-':
            o.number = obj1->number - obj2->number;
            break;
        case '*':
            o.number = obj1->number * obj2->number;
            break;
        case '/':
            o.number = obj1->number / obj2->number;
            break;
        default:
            o = *obj1;
    }
    return o;
}

Object add(Object obj1, Object obj2)
    { return basicOp(&obj1, &obj2, '+'); }

Object sub(Object obj1, Object obj2)
    { return basicOp(&obj1, &obj2, '-'); }

Object mul(Object obj1, Object obj2)
    { return basicOp(&obj1, &obj2, '*'); }

Object divi(Object obj1, Object obj2)
    { return basicOp(&obj1, &obj2, '/'); }

void addFunc(const char *name, Object (*func)(Object, Object), 
               struct Environment *env)
{
    int i;
    for(i = 0; i < MAX_ENV_ELM; i++) {
        if(env->strings[i] == NULL) {
            //printf("Adding at %d\n", i);
            env->strings[i] = malloc(sizeof(name));
            strncpy(env->strings[i], name, MAX_TOK_LEN);
            Object o;
            o.type = TYPE_FUNC;
            o.forward = NULL;
            o.func = func;
            env->objects[i] = o;
            break;
        }
    }
}

struct Environment defaultEnv() {
    struct Environment e;
    e.strings = malloc(sizeof(char*) * MAX_ENV_ELM);
    e.objects = malloc(sizeof(Object) * MAX_ENV_ELM);
    addFunc("+", &add, &e);
    addFunc("-", &sub, &e);
    addFunc("*", &mul, &e);
    addFunc("/", &divi, &e);

    /*
    e.strings[0] = malloc(sizeof("+"));
    strncpy(e.strings[0], "+", MAX_TOK_LEN);
    Object o;
    o.type = TYPE_FUNC;
    o.forward = NULL;
    o.func = &add;
    e.objects[0] = o;
    */
    return e;
}

Object parseEval(const char *input, struct Environment *env)
{
    struct Slice *tokens = tokenize(input);
    struct Slice *debug = tokens;
#ifdef STANDALONE
    if(debug) {
        while(debug->text) {
            char tok[MAX_TOK_LEN];
            copySlice(tok, debug);
            // printf("'%s', ", tok);
            debug++;
        }
        // printf("\n");
    } else {
        // printf("parse error\n");
    }
    // printf("parseEval() parse()\n");
#endif
    Object parsed = parse(tokens).obj;
    return eval(&parsed, env);
}

#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);
        printf("eval: %d\n", obj.number);
        break;
    }
}

int main(void)
{
    struct Environment env = defaultEnv();
    if(1) {
        repl(&env);
    } else {
        struct Slice *tokens = tokenize("(+ 10 5)");
        struct Slice *debug = tokens;

        if(debug) {
            while(debug->text) {
                char tok[10];
                copySlice(tok, debug);
                printf("'%s', ", tok);
                debug++;
            }
            printf("\n");
        } else {
            printf("parse error\n");
        }
        parse(tokens);
    }
}
#endif