#include "generator.h"
#include "coroutine.h"
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>

enum {
    Generator_Running,
    Generator_Deleting,
    Generator_Complete
};

struct Generator {
    Coroutine *coroutine;
    Coroutine *caller;
    void *(*start)(void *);
    void *param;
    char state;
};

static void on_yield(void *this){
    Generator *gen = (Generator *)this;
    Coroutine_Continue(gen->caller, Coroutine_GetValue(gen->coroutine), true);
}

static void *do_start(void *this){
    Generator *gen = (Generator *)this;
    assert(gen->state == Generator_Running || gen->state == Generator_Deleting);
    void *value;
    if (gen->state == Generator_Running){
        value = gen->start(gen->param);
    } else {
        // we are being deleted
        value = NULL;
    }
    gen->state = Generator_Complete;
    Coroutine_Continue(gen->caller, value, true);
    return value;
}

Generator *Generator_New(void *(*start)(void *), void *param){
    Generator *gen = malloc(sizeof(Generator));
    gen->start = start;
    gen->param = param;
    gen->coroutine = Coroutine_New(gen, on_yield, do_start);
    gen->state = Generator_Running;
    return gen;
}

void Generator_Delete(Generator *gen){
    assert(gen->state != Generator_Deleting);
    if (gen->state == Generator_Running){
        gen->state = Generator_Deleting;
        gen->caller = Coroutine_GetActive();
        Coroutine_Continue(gen->coroutine, gen, true);
        Coroutine_Yield(NULL);
    }
    assert(gen->state == Generator_Complete);
    Coroutine_Delete(gen->coroutine);
    free(gen);
}

bool Generator_Next(Generator *gen, void **value){
    assert(gen->state != Generator_Deleting);
    if (gen->state == Generator_Complete){
        return false;
    }
    gen->caller = Coroutine_GetActive();
    Coroutine_Continue(gen->coroutine, gen, true);
    *value = Coroutine_Yield(NULL);
    return Coroutine_IsRunning(gen->coroutine);
}

bool Generator_Yield(void *value)
{
    Generator *gen = Coroutine_Yield(value);
    return gen->state == Generator_Running;
}