//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Disk load indicator.
//

#include "doomtype.h"
#include "deh_str.h"
#include "i_swap.h"
#include "i_video.h"
#include "m_argv.h"
#include "v_video.h"
#include "w_wad.h"
#include "z_zone.h"

#include "v_diskicon.h"

// Only display the disk icon if more then this much bytes have been read
// during the previous tic.

static const int diskicon_threshold = 20*1024;

// Two buffers: disk_data contains the data representing the disk icon
// (raw, not a patch_t) while saved_background is an equivalently-sized
// buffer where we save the background data while the disk is on screen.
static byte *disk_data;
static byte *saved_background;

static int loading_disk_xoffs = 0;
static int loading_disk_yoffs = 0;

// Number of bytes read since the last call to V_DrawDiskIcon().
static size_t recent_bytes_read = 0;
static boolean disk_drawn;

static void CopyRegion(byte *dest, int dest_pitch,
                       byte *src, int src_pitch,
                       int w, int h)
{
    byte *s, *d;
    int y;

    s = src; d = dest;
    for (y = 0; y < h; ++y)
    {
        memcpy(d, s, w * sizeof(*d));
        s += src_pitch;
        d += dest_pitch;
    }
}

static void SaveDiskData(char *disk_lump, int xoffs, int yoffs)
{
    byte *tmpscreen;
    patch_t *disk;

    // Allocate a complete temporary screen where we'll draw the patch.
    tmpscreen = Z_Malloc(SCREENWIDTH * SCREENHEIGHT * sizeof(*tmpscreen),
                         PU_STATIC, NULL);
    memset(tmpscreen, 0, SCREENWIDTH * SCREENHEIGHT * sizeof(*tmpscreen));
    V_UseBuffer(tmpscreen);

    // Buffer where we'll save the disk data.
    disk_data = Z_Malloc(LOADING_DISK_W * LOADING_DISK_H * sizeof(*disk_data),
                         PU_STATIC, NULL);

    // Draw the patch and save the result to disk_data.
    disk = W_CacheLumpName(disk_lump, PU_STATIC);
    V_DrawPatch(loading_disk_xoffs, loading_disk_yoffs, disk);
    CopyRegion(disk_data, LOADING_DISK_W,
               tmpscreen + yoffs * SCREENWIDTH + xoffs, SCREENWIDTH,
               LOADING_DISK_W, LOADING_DISK_H);
    W_ReleaseLumpName(disk_lump);

    V_RestoreBuffer();
    Z_Free(tmpscreen);
}

void V_EnableLoadingDisk(char *lump_name, int xoffs, int yoffs)
{
    loading_disk_xoffs = xoffs;
    loading_disk_yoffs = yoffs;

    saved_background = Z_Malloc(LOADING_DISK_W * LOADING_DISK_H
                                 * sizeof(*saved_background),
                                PU_STATIC, NULL);
    SaveDiskData(lump_name, xoffs, yoffs);
}

void V_BeginRead(size_t nbytes)
{
    recent_bytes_read += nbytes;
}

static byte *DiskRegionPointer(void)
{
    return I_VideoBuffer
         + loading_disk_yoffs * SCREENWIDTH
         + loading_disk_xoffs;
}

void V_DrawDiskIcon(void)
{
    if (disk_data != NULL && recent_bytes_read > diskicon_threshold)
    {
        // Save the background behind the disk before we draw it.
        CopyRegion(saved_background, LOADING_DISK_W,
                   DiskRegionPointer(), SCREENWIDTH,
                   LOADING_DISK_W, LOADING_DISK_H);

        // Write the disk to the screen buffer.
        CopyRegion(DiskRegionPointer(), SCREENWIDTH,
                   disk_data, LOADING_DISK_W,
                   LOADING_DISK_W, LOADING_DISK_H);
        disk_drawn = true;
    }

    recent_bytes_read = 0;
}

void V_RestoreDiskBackground(void)
{
    if (disk_drawn)
    {
        // Restore the background.
        CopyRegion(DiskRegionPointer(), SCREENWIDTH,
                   saved_background, LOADING_DISK_W,
                   LOADING_DISK_W, LOADING_DISK_H);

        disk_drawn = false;
    }
}

