/*
** The status of an annotation operation is recorded by an instance
** of the following structure.
*/
typedef struct Annotator Annotator;
struct Annotator {
  DContext c;       /* The diff-engine context */
  struct AnnLine {  /* Lines of the original files... */
    const char *z;       /* The text of the line */
    short int n;         /* Number of bytes (omitting trailing space and \n) */
    short int iLevel;    /* Level at which tag was set */
    const char *zSrc;    /* Tag showing origin of this line */
  } *aOrig;
  int nOrig;        /* Number of elements in aOrig[] */
  int nNoSrc;       /* Number of entries where aOrig[].zSrc==NULL */
  int iLevel;       /* Current level */
  int nVers;        /* Number of versions analyzed */
  char **azVers;    /* Names of versions analyzed */
};

/*
** Initialize the annotation process by specifying the file that is
** to be annotated.  The annotator takes control of the input Blob and

** if additional annotation is required.  zPName is the tag to insert
** on each line of the file being annotated that was contributed by
** pParent.  Memory to hold zPName is leaked.
*/
static int annotation_step(Annotator *p, Blob *pParent, char *zPName){
  int i, j;
  int lnTo;
  int iPrevLevel;
  int iThisLevel;

  /* Prepare the parent file to be diffed */
  p->c.aFrom = break_into_lines(blob_str(pParent), blob_size(pParent),
                                &p->c.nFrom, 1);
  if( p->c.aFrom==0 ){
    return 1;
  }

  /* Compute the differences going from pParent to the file being
  ** annotated. */
  diff_all(&p->c);

  /* Where new lines are inserted on this difference, record the
  ** zPName as the source of the new line.
  */
  iPrevLevel = p->iLevel;
  p->iLevel++;
  iThisLevel = p->iLevel;
  for(i=lnTo=0; i<p->c.nEdit; i+=3){
    struct AnnLine *x = &p->aOrig[lnTo];
    for(j=0; j<p->c.aEdit[i]; j++, lnTo++, x++){
      if( x->zSrc==0 || x->iLevel==iPrevLevel ){
         x->zSrc = zPName;
         x->iLevel = iThisLevel;
      }
    }
    lnTo += p->c.aEdit[i+2];
  }

  /* Clear out the diff results */
  free(p->c.aEdit);
  p->c.aEdit = 0;