#include "tape.h"
#include "common.h"
#include <stdlib.h>
#include <memory.h>
#include <string.h>

tape_t* tape_open(const char* filename, const char* mode)
{
    file_t *file = file_open(filename, mode);
    printfv(VERBOSITY_VERBOSE, "Opening file %s in mode %s.\n", filename, mode);
   
    if (!file) {
        fprintf(stderr, "Cannot open %s in %s mode.", filename, mode);
        return NULL;
    }

    tape_t* tape = malloc(sizeof(tape_t));

    fseek(file->file, 0, SEEK_END);

    tape->file = file;
    tape->end  = ftell(file->file);

    return tape;
}

void tape_close(tape_t* tape)
{
    file_close(tape->file);
}

void* tape_read(tape_t* tape, offset_t offset, void* record, size_t size)
{
    char buffer[PAGE_SIZE];

    page_t page = offset / PAGE_SIZE;
    offset      = offset % PAGE_SIZE;

    offset_t written = 0;
    file_read(tape->file, page, buffer, PAGE_SIZE);

    while (size > PAGE_SIZE - offset) {
        memcpy(record + written, buffer + offset, PAGE_SIZE - offset);

        size    -= PAGE_SIZE - offset;
        written += PAGE_SIZE - offset;

        page++;
        offset = 0;

        file_read(tape->file, page, buffer, PAGE_SIZE);
    }

    memcpy(record + written, buffer + offset, size);

    return record;
}

offset_t tape_write(tape_t* tape, offset_t location, void* record, size_t size)
{
    char buffer[PAGE_SIZE];

    page_t   page   = location / PAGE_SIZE;
    offset_t offset = location % PAGE_SIZE;

    offset_t written = 0;
    size_t original = file_read(tape->file, page, buffer, PAGE_SIZE);
    while (size > PAGE_SIZE - offset) {
        memcpy(buffer + offset, record + written, PAGE_SIZE - offset);

        size    -= PAGE_SIZE - offset;
        written += PAGE_SIZE - offset;

        file_write(tape->file, page, buffer, PAGE_SIZE);

        page++;
        offset = 0;
        
        file_read(tape->file, page, buffer, PAGE_SIZE);
    }

    memcpy(buffer + offset, record + written, size);
    file_write(tape->file, page, buffer, offset + size > original ? offset + size : original);

    written += size;
    if (location + written > tape->end) {
        tape->end = location + written; 
    }

    return location;
}

offset_t tape_append(tape_t* tape, void* record, size_t size)
{
    return tape_write(tape, tape->end, record, size);
}