
/* GStreamer
 * Copyright (C) 2003 Christophe Fergeau <teuf@gnome.org>
 *
 * gstflactag.c: plug-in for reading/modifying vorbis comments in flac files
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gst/gsttagsetter.h>
#include <gst/tag/tag.h>
#include <string.h>

#define GST_TYPE_FLAC_TAG (gst_flac_tag_get_type())
#define GST_FLAC_TAG(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_FLAC_TAG, GstFlacTag))
#define GST_FLAC_TAG_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_FLAC_TAG, GstFlacTag))
#define GST_IS_FLAC_TAG(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_FLAC_TAG))
#define GST_IS_FLAC_TAG_CLASS(obj) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_FLAC_TAG))

typedef struct _GstFlacTag GstFlacTag;
typedef struct _GstFlacTagClass GstFlacTagClass;

static inline gint
min (gint a, gint b)
{
  if (a < b) {
    return a;
  } else {
    return b;
  }
}


typedef enum
{
  GST_FLAC_TAG_STATE_INIT,
  GST_FLAC_TAG_STATE_METADATA_BLOCKS,
  GST_FLAC_TAG_STATE_METADATA_NEXT_BLOCK,
  GST_FLAC_TAG_STATE_WRITING_METADATA_BLOCK,
  GST_FLAC_TAG_STATE_VC_METADATA_BLOCK,
  GST_FLAC_TAG_STATE_ADD_VORBIS_COMMENT,
  GST_FLAC_TAG_STATE_AUDIO_DATA
}
GstFlacTagState;


struct _GstFlacTag
{
  GstElement element;

  /* pads */
  GstPad *sinkpad;
  GstPad *srcpad;

  GstFlacTagState state;

  GstBuffer *buffer;
  GstBuffer *vorbiscomment;
  GstTagList *tags;

  guint metadata_bytes_remaining;
  gboolean metadata_last_block;

  gboolean only_output_tags;
};

struct _GstFlacTagClass
{
  GstElementClass parent_class;
};

/* elementfactory information */
static GstElementDetails gst_flac_tag_details =
GST_ELEMENT_DETAILS ("flac retagger",
    "Tag",
    "Rewrite tags in a FLAC file",
    "Christope Fergeau <teuf@gnome.org>");


/* signals and args */
enum
{
  /* FILL ME */
  LAST_SIGNAL
};

enum
{
  ARG_0
      /* FILL ME */
};

static GstStaticPadTemplate flac_tag_src_template =
    GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("audio/x-flac; application/x-gst-tags")
    );

static GstStaticPadTemplate flac_tag_sink_template =
GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("audio/x-flac")
    );


static void gst_flac_tag_base_init (gpointer g_class);
static void gst_flac_tag_class_init (GstFlacTagClass * klass);
static void gst_flac_tag_init (GstFlacTag * tag);

static void gst_flac_tag_chain (GstPad * pad, GstData * data);

static GstStateChangeReturn gst_flac_tag_change_state (GstElement * element,
    GstStateChange transition);


static GstElementClass *parent_class = NULL;

/* static guint gst_flac_tag_signals[LAST_SIGNAL] = { 0 }; */

GType
gst_flac_tag_get_type (void)
{
  static GType flac_tag_type = 0;

  if (!flac_tag_type) {
    static const GTypeInfo flac_tag_info = {
      sizeof (GstFlacTagClass),
      gst_flac_tag_base_init,
      NULL,
      (GClassInitFunc) gst_flac_tag_class_init,
      NULL,
      NULL,
      sizeof (GstFlacTag),
      0,
      (GInstanceInitFunc) gst_flac_tag_init,
    };
    static const GInterfaceInfo tag_setter_info = {
      NULL,
      NULL,
      NULL
    };

    flac_tag_type =
        g_type_register_static (GST_TYPE_ELEMENT, "GstFlacTag", &flac_tag_info,
        0);

    g_type_add_interface_static (flac_tag_type, GST_TYPE_TAG_SETTER,
        &tag_setter_info);

  }
  return flac_tag_type;
}


static void
gst_flac_tag_base_init (gpointer g_class)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_set_details (element_class, &gst_flac_tag_details);

  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&flac_tag_sink_template));
  gst_element_class_add_pad_template (element_class,
      gst_static_pad_template_get (&flac_tag_src_template));
}


static void
send_eos (GstFlacTag * tag)
{
  gst_element_set_eos (GST_ELEMENT (tag));
  gst_pad_push (tag->srcpad, GST_DATA (gst_event_new (GST_EVENT_EOS)));
  /* Seek to end of sink stream */
  if (gst_pad_send_event (GST_PAD_PEER (tag->sinkpad),
          gst_event_new_seek (GST_FORMAT_BYTES | GST_SEEK_METHOD_END |
              GST_SEEK_FLAG_FLUSH, 0))) {
  } else {
    g_warning ("Couldn't seek to eos on sinkpad\n");
  }
}


static gboolean
caps_nego (GstFlacTag * tag)
{
  /* do caps nego */
  GstCaps *caps;

  caps = gst_caps_new_simple ("audio/x-flac", NULL);
  if (gst_pad_try_set_caps (tag->srcpad, caps) != GST_PAD_LINK_REFUSED) {
    tag->only_output_tags = FALSE;
    GST_LOG_OBJECT (tag, "normal operation, using audio/x-flac output");
  } else {
    if (gst_pad_try_set_caps (tag->srcpad,
            gst_caps_new_simple ("application/x-gst-tags", NULL))
        != GST_PAD_LINK_REFUSED) {
      tag->only_output_tags = TRUE;
      GST_LOG_OBJECT (tag, "fast operation, just outputting tags");
      printf ("output tags only\n");
    } else {
      return FALSE;
    }
  }
  return TRUE;
}

static void
gst_flac_tag_class_init (GstFlacTagClass * klass)
{
  GstElementClass *gstelement_class;
  GObjectClass *gobject_class;

  gstelement_class = (GstElementClass *) klass;
  gobject_class = (GObjectClass *) klass;

  parent_class = g_type_class_ref (GST_TYPE_ELEMENT);

  gstelement_class->change_state = gst_flac_tag_change_state;
}


static void
gst_flac_tag_init (GstFlacTag * tag)
{
  /* create the sink and src pads */
  tag->sinkpad =
      gst_pad_new_from_template (gst_static_pad_template_get
      (&flac_tag_sink_template), "sink");
  gst_element_add_pad (GST_ELEMENT (tag), tag->sinkpad);
  gst_pad_set_chain_function (tag->sinkpad,
      GST_DEBUG_FUNCPTR (gst_flac_tag_chain));

  tag->srcpad =
      gst_pad_new_from_template (gst_static_pad_template_get
      (&flac_tag_src_template), "src");
  gst_element_add_pad (GST_ELEMENT (tag), tag->srcpad);

  tag->buffer = NULL;
}

#define FLAC_MAGIC "fLaC"
#define FLAC_MAGIC_SIZE (sizeof (FLAC_MAGIC) - 1)

static void
gst_flac_tag_chain (GstPad * pad, GstData * data)
{
  GstBuffer *buffer;
  GstFlacTag *tag;

  if (GST_IS_EVENT (data)) {
    g_print ("Unhandled event\n");
    return;
  }

  buffer = GST_BUFFER (data);
  tag = GST_FLAC_TAG (gst_pad_get_parent (pad));

  if (tag->buffer) {
    GstBuffer *merge;

    merge = gst_buffer_merge (tag->buffer, buffer);
    gst_buffer_unref (buffer);
    gst_buffer_unref (tag->buffer);
    tag->buffer = merge;
  } else {
    tag->buffer = buffer;
  }


  /* Initial state, we don't even know if we are dealing with a flac file */
  if (tag->state == GST_FLAC_TAG_STATE_INIT) {
    if (!caps_nego (tag)) {
      return;
    }

    if (GST_BUFFER_SIZE (tag->buffer) < sizeof (FLAC_MAGIC)) {
      return;
    }

    if (strncmp (GST_BUFFER_DATA (tag->buffer), FLAC_MAGIC,
            FLAC_MAGIC_SIZE) == 0) {
      GstBuffer *sub;

      tag->state = GST_FLAC_TAG_STATE_METADATA_BLOCKS;
      sub = gst_buffer_create_sub (tag->buffer, 0, FLAC_MAGIC_SIZE);

      gst_pad_push (tag->srcpad, GST_DATA (sub));
      sub =
          gst_buffer_create_sub (tag->buffer, FLAC_MAGIC_SIZE,
          GST_BUFFER_SIZE (tag->buffer) - FLAC_MAGIC_SIZE);
      gst_buffer_unref (tag->buffer);
      /* We do a copy because we need a writable buffer, and _create_sub
       * sets the buffer it uses to read-only
       */
      tag->buffer = gst_buffer_copy (sub);
      gst_buffer_unref (sub);
    } else {
      /* FIXME: does that work well with FLAC files containing ID3v2 tags ? */
      GST_ELEMENT_ERROR (tag, STREAM, WRONG_TYPE, (NULL), (NULL));
    }
  }


  /* The fLaC magic string has been skipped, try to detect the beginning
   * of a metadata block
   */
  if (tag->state == GST_FLAC_TAG_STATE_METADATA_BLOCKS) {
    guint size;
    guint type;
    gboolean is_last;

    g_assert (tag->metadata_bytes_remaining == 0);
    g_assert (tag->metadata_last_block == FALSE);

    /* The header of a flac metadata block is 4 bytes long:
     * 1st bit: indicates whether this is the last metadata info block
     * 7 next bits: 4 if vorbis comment block
     * 24 next bits: size of the metadata to follow (big endian)
     */
    if (GST_BUFFER_SIZE (tag->buffer) < 4) {
      return;
    }
    is_last = (((GST_BUFFER_DATA (tag->buffer)[0]) & 0x80) == 0x80);
    /* If we have metadata set on the element, the last metadata block 
     * will be the vorbis comment block which we will build ourselves
     */
    if (is_last) {
      (GST_BUFFER_DATA (tag->buffer)[0]) &= (~0x80);
    }

    type = (GST_BUFFER_DATA (tag->buffer)[0]) & 0x7F;
    size = ((GST_BUFFER_DATA (tag->buffer)[1]) << 16)
        | ((GST_BUFFER_DATA (tag->buffer)[2]) << 8)
        | (GST_BUFFER_DATA (tag->buffer)[3]);

    /* The 4 bytes long header isn't included in the metadata size */
    tag->metadata_bytes_remaining = size + 4;
    tag->metadata_last_block = is_last;

    /* Metadata blocks of type 4 are vorbis comment blocks */
    if (type == 0x04) {
      tag->state = GST_FLAC_TAG_STATE_VC_METADATA_BLOCK;
    } else {
      tag->state = GST_FLAC_TAG_STATE_WRITING_METADATA_BLOCK;
    }
  }


  /* Reads a metadata block */
  if ((tag->state == GST_FLAC_TAG_STATE_WRITING_METADATA_BLOCK) ||
      (tag->state == GST_FLAC_TAG_STATE_VC_METADATA_BLOCK)) {
    GstBuffer *sub;
    guint bytes_to_push;

    g_assert (tag->metadata_bytes_remaining != 0);

    bytes_to_push = min (tag->metadata_bytes_remaining,
        GST_BUFFER_SIZE (tag->buffer));

    sub = gst_buffer_create_sub (tag->buffer, 0, bytes_to_push);

    if (tag->state == GST_FLAC_TAG_STATE_WRITING_METADATA_BLOCK) {
      gst_pad_push (tag->srcpad, GST_DATA (sub));
    } else {
      if (tag->vorbiscomment == NULL) {
        tag->vorbiscomment = sub;
      } else {
        GstBuffer *merge;

        merge = gst_buffer_merge (tag->vorbiscomment, sub);
        gst_buffer_unref (tag->vorbiscomment);
        gst_buffer_unref (sub);
        tag->vorbiscomment = merge;
      }
    }

    tag->metadata_bytes_remaining -= (bytes_to_push);

    if (GST_BUFFER_SIZE (tag->buffer) > bytes_to_push) {
      GstBuffer *sub;

      sub = gst_buffer_create_sub (tag->buffer, bytes_to_push,
          GST_BUFFER_SIZE (tag->buffer) - bytes_to_push);
      gst_buffer_unref (tag->buffer);

      /* We make a copy because we need a writable buffer, and _create_sub
       * sets the buffer it uses to read-only
       */
      tag->buffer = gst_buffer_copy (sub);
      gst_buffer_unref (sub);

      tag->state = GST_FLAC_TAG_STATE_METADATA_NEXT_BLOCK;
    } else if (tag->metadata_bytes_remaining == 0) {
      gst_buffer_unref (tag->buffer);
      tag->buffer = NULL;
      tag->state = GST_FLAC_TAG_STATE_METADATA_NEXT_BLOCK;
      tag->buffer = NULL;
    } else {
      tag->state = GST_FLAC_TAG_STATE_WRITING_METADATA_BLOCK;
      tag->buffer = NULL;
    }
  }

  /* This state is mainly used to be able to stop as soon as we read
   * a vorbiscomment block from the flac file if we are in an only output
   * tags mode
   */
  if (tag->state == GST_FLAC_TAG_STATE_METADATA_NEXT_BLOCK) {
    /* Check if in the previous iteration we read a vorbis comment metadata 
     * block, and stop now if the user only wants to read tags
     */
    if (tag->vorbiscomment != NULL) {
      /* We found some tags, try to parse them and notify the other elements
       * that we encoutered some tags
       */
      tag->tags = gst_tag_list_from_vorbiscomment_buffer (tag->vorbiscomment,
          GST_BUFFER_DATA (tag->vorbiscomment), 4, NULL);
      if (tag->tags != NULL) {
        gst_element_found_tags (GST_ELEMENT (tag), tag->tags);
      }

      gst_buffer_unref (tag->vorbiscomment);
      tag->vorbiscomment = NULL;

      if (tag->only_output_tags) {
        send_eos (tag);
        return;
      }
    }

    /* Skip to next state */
    if (tag->metadata_last_block == FALSE) {
      tag->state = GST_FLAC_TAG_STATE_METADATA_BLOCKS;
    } else {
      if (tag->only_output_tags) {
        /* If we finished parsing the metadata blocks, we will never find any
         * metadata, so just stop now
         */
        send_eos (tag);
        return;
      } else {
        tag->state = GST_FLAC_TAG_STATE_ADD_VORBIS_COMMENT;
      }
    }
  }


  /* Creates a vorbis comment block from the metadata which was set
   * on the gstreamer element, and add it to the flac stream
   */
  if (tag->state == GST_FLAC_TAG_STATE_ADD_VORBIS_COMMENT) {
    GstBuffer *buffer;
    gint size;
    const GstTagList *user_tags;
    GstTagList *merged_tags;

    g_assert (tag->only_output_tags == FALSE);

    user_tags = gst_tag_setter_get_list (GST_TAG_SETTER (tag));
    merged_tags = gst_tag_list_merge (tag->tags, user_tags,
        gst_tag_setter_get_merge_mode (GST_TAG_SETTER (tag)));

    if (merged_tags == NULL) {
      /* If we get a NULL list of tags, we must generate a padding block
       * which is marked as the last metadata block, otherwise we'll
       * end up with a corrupted flac file.
       */
      g_warning ("No tags found\n");
      buffer = gst_buffer_new_and_alloc (12);
      if (buffer == NULL) {
        GST_ELEMENT_ERROR (tag, CORE, TOO_LAZY, (NULL),
            ("Error creating 12-byte buffer for padding block"));
      }
      memset (GST_BUFFER_DATA (buffer), 0, GST_BUFFER_SIZE (buffer));
      GST_BUFFER_DATA (buffer)[0] = 0x81;       /* 0x80 = Last metadata block, 
                                                 * 0x01 = padding block
                                                 */
    } else {
      guchar header[4];

      memset (header, 0, sizeof (header));
      header[0] = 0x84;         /* 0x80 = Last metadata block, 
                                 * 0x04 = vorbiscomment block
                                 */
      buffer = gst_tag_list_to_vorbiscomment_buffer (merged_tags, header,
          sizeof (header), NULL);
      gst_tag_list_free (merged_tags);
      if (buffer == NULL) {
        GST_ELEMENT_ERROR (tag, CORE, TAG, (NULL),
            ("Error converting tag list to vorbiscomment buffer"));
        return;
      }
      size = GST_BUFFER_SIZE (buffer) - 4;
      if ((size > 0xFFFFFF) || (size < 0)) {
        /* FLAC vorbis comment blocks are limited to 2^24 bytes, 
         * while the vorbis specs allow more than that. Shouldn't 
         * be a real world problem though
         */
        GST_ELEMENT_ERROR (tag, CORE, TAG, (NULL),
            ("Vorbis comment of size %d too long", size));
        return;
      }

      /* Get rid of the framing bit at the end of the vorbiscomment buffer 
       * if it exists since libFLAC seems to lose sync because of this
       * bit in gstflacdec
       */
      if (GST_BUFFER_DATA (buffer)[GST_BUFFER_SIZE (buffer) - 1] == 1) {
        GstBuffer *sub;

        sub = gst_buffer_create_sub (buffer, 0, GST_BUFFER_SIZE (buffer) - 1);
        gst_buffer_unref (buffer);
        buffer = sub;
      }
    }

    /* The 4 byte metadata block header isn't accounted for in the total
     * size of the metadata block
     */
    size = GST_BUFFER_SIZE (buffer) - 4;

    GST_BUFFER_DATA (buffer)[1] = ((size & 0xFF0000) >> 16);
    GST_BUFFER_DATA (buffer)[2] = ((size & 0x00FF00) >> 8);
    GST_BUFFER_DATA (buffer)[3] = (size & 0x0000FF);
    gst_pad_push (tag->srcpad, GST_DATA (buffer));
    tag->state = GST_FLAC_TAG_STATE_AUDIO_DATA;
  }


  /* The metadata blocks have been read, now we are reading audio data */
  if (tag->state == GST_FLAC_TAG_STATE_AUDIO_DATA) {
    gst_pad_push (tag->srcpad, GST_DATA (tag->buffer));
    tag->buffer = NULL;
  }
}


static GstStateChangeReturn
gst_flac_tag_change_state (GstElement * element, GstStateChange transition)
{
  GstFlacTag *tag;

  tag = GST_FLAC_TAG (element);

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      break;
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      break;
    case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
      /* do something to get out of the chain function faster */
      break;
    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
      break;
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      if (tag->buffer) {
        gst_buffer_unref (tag->buffer);
        tag->buffer = NULL;
      }
      if (tag->vorbiscomment) {
        gst_buffer_unref (tag->vorbiscomment);
        tag->vorbiscomment = NULL;
      }
      if (tag->tags) {
        gst_tag_list_free (tag->tags);
      }
      tag->state = GST_FLAC_TAG_STATE_INIT;
      break;
    case GST_STATE_CHANGE_READY_TO_NULL:
      break;
  }

  return parent_class->change_state (element, transition);
}
