#include "io_backend.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// === Static variables

static struct iob_context context;
static FILE *input = NULL;
static char *stream_buf = NULL;
static size_t stream_buf_size = 0;
static enum iob_state state = IOB_STATE_NOT_INITIALIZED;

// === Functions

int iob_init(struct iob_context *ctx)
{
    if (state != IOB_STATE_NOT_INITIALIZED)
        return IOB_ERROR_MODULE_NOT_INITIALIZED;

    context = *ctx;

    switch (context.mode)
    {
    case IOB_MODE_STDIN:
        input = stdin;
        state = IOB_STATE_READY;
        return 0;

    case IOB_MODE_SCRIPT:
        if (context.args == NULL)
            return IOB_ERROR_BAD_ARG;
        input = fopen(context.args, "r");
        if (input == NULL)
            return IOB_ERROR_CANNOT_OPEN_FILE;
        state = IOB_STATE_READY;
        return 0;

    case IOB_MODE_CMD:
        if (context.args != NULL)
            return IOB_ERROR_BAD_ARG;
        state = IOB_STATE_READY;
        return 0;

    default:
        return IOB_ERROR_BAD_ARG;
    }
}

void iob_close(void)
{
    fclose(input);
    if ((context.mode == IOB_MODE_STDIN || context.mode == IOB_MODE_SCRIPT)
        && stream_buf != NULL)
    {
        free(stream_buf);
        stream_buf_size = 0;
    }
    state = IOB_STATE_NOT_INITIALIZED;
}

ssize_t stream_read(char **stream)
{
    // Check args
    if (stream == NULL)
        return IOB_ERROR_BAD_ARG;

    // Check env
    if (state == IOB_STATE_NOT_INITIALIZED)
        return IOB_ERROR_MODULE_NOT_INITIALIZED;
    if (state == IOB_STATE_FINISHED)
        return 0;
    if (state == IOB_STATE_ERROR)
        return IOB_ERROR_GENERIC;

    // Use input
    if (context.mode == IOB_MODE_STDIN || context.mode == IOB_MODE_SCRIPT)
    {
        ssize_t nread = getline(&stream_buf, &stream_buf_size, input);
        if (nread == -1)
        {
            state = IOB_STATE_FINISHED;
            return 0;
        }
        else if (nread < 0)
            state = IOB_STATE_ERROR;

        return nread;
    }
    // Use args
    else if (context.mode == IOB_MODE_CMD)
    {
        *stream = context.args;
        return strlen(context.args);
    }
    else
    {
        *stream = NULL;
        return IOB_ERROR_GENERIC;
    }
}