/*

 * Low level 3-way in-core file merge.

 *

 * Copyright (c) 2007 Junio C Hamano

 */

#define USE_THE_REPOSITORY_VARIABLE

#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"

#include "config.h"

#include "convert.h"

#include "attr.h"

#include "xdiff-interface.h"

#include "run-command.h"

#include "merge-ll.h"

#include "quote.h"

#include "strbuf.h"

#include "gettext.h"

#include "tempfile.h"

struct ll_merge_driver;

typedef enum ll_merge_result (*ll_merge_fn)(const struct ll_merge_driver *,

         mmfile_t *result,

         const char *path,

         mmfile_t *orig, const char *orig_name,

         mmfile_t *src1, const char *name1,

         mmfile_t *src2, const char *name2,

         const struct ll_merge_options *opts,

         int marker_size);

struct ll_merge_driver {

  const char *name;

  const char *description;

  ll_merge_fn fn;

  char *recursive;

  struct ll_merge_driver *next;

  char *cmdline;

};

static struct attr_check *merge_attributes;

static struct attr_check *load_merge_attributes(void)

{

  if (!merge_attributes)

    merge_attributes = attr_check_initl("merge", "conflict-marker-size", NULL);

  return merge_attributes;

}

void reset_merge_attributes(void)

{

  attr_check_free(merge_attributes);

  merge_attributes = NULL;

}

/*

 * Built-in low-levels

 */

static enum ll_merge_result ll_binary_merge(const struct ll_merge_driver *drv UNUSED,

         mmfile_t *result,

         const char *path UNUSED,

         mmfile_t *orig, const char *orig_name UNUSED,

         mmfile_t *src1, const char *name1 UNUSED,

         mmfile_t *src2, const char *name2 UNUSED,

         const struct ll_merge_options *opts,

         int marker_size UNUSED)

{

  enum ll_merge_result ret;

  mmfile_t *stolen;

  assert(opts);

  /*

   * The tentative merge result is the common ancestor for an

   * internal merge.  For the final merge, it is "ours" by

   * default but -Xours/-Xtheirs can tweak the choice.

   */

  if (opts->virtual_ancestor) {

    stolen = orig;

    ret = LL_MERGE_OK;

  } else {

    switch (opts->variant) {

    default:

      ret = LL_MERGE_BINARY_CONFLICT;

      stolen = src1;

      break;

    case XDL_MERGE_FAVOR_OURS:

      ret = LL_MERGE_OK;

      stolen = src1;

      break;

    case XDL_MERGE_FAVOR_THEIRS:

      ret = LL_MERGE_OK;

      stolen = src2;

      break;

    }

  }

  result->ptr = stolen->ptr;

  result->size = stolen->size;

  stolen->ptr = NULL;

  return ret;

}

static enum ll_merge_result ll_xdl_merge(const struct ll_merge_driver *drv_unused,

      mmfile_t *result,

      const char *path,

      mmfile_t *orig, const char *orig_name,

      mmfile_t *src1, const char *name1,

      mmfile_t *src2, const char *name2,

      const struct ll_merge_options *opts,

      int marker_size)

{

  enum ll_merge_result ret;

  xmparam_t xmp;

  int status;

  assert(opts);

  if (orig->size > MAX_XDIFF_SIZE ||

      src1->size > MAX_XDIFF_SIZE ||

      src2->size > MAX_XDIFF_SIZE ||

      buffer_is_binary(orig->ptr, orig->size) ||

      buffer_is_binary(src1->ptr, src1->size) ||

      buffer_is_binary(src2->ptr, src2->size)) {

    return ll_binary_merge(drv_unused, result,

               path,

               orig, orig_name,

               src1, name1,

               src2, name2,

               opts, marker_size);

  }

  memset(&xmp, 0, sizeof(xmp));

  xmp.level = XDL_MERGE_ZEALOUS;

  xmp.favor = opts->variant;

  xmp.xpp.flags = opts->xdl_opts;

  if (opts->conflict_style >= 0)

    xmp.style = opts->conflict_style;

  else if (git_xmerge_style >= 0)

    xmp.style = git_xmerge_style;

  if (marker_size > 0)

    xmp.marker_size = marker_size;

  xmp.ancestor = orig_name;

  xmp.file1 = name1;

  xmp.file2 = name2;

  status = xdl_merge(orig, src1, src2, &xmp, result);

  ret = (status > 0) ? LL_MERGE_CONFLICT : status;

  return ret;

}

static enum ll_merge_result ll_union_merge(const struct ll_merge_driver *drv_unused,

        mmfile_t *result,

        const char *path,

        mmfile_t *orig, const char *orig_name,

        mmfile_t *src1, const char *name1,

        mmfile_t *src2, const char *name2,

        const struct ll_merge_options *opts,

        int marker_size)

{

  /* Use union favor */

  struct ll_merge_options o;

  assert(opts);

  o = *opts;

  o.variant = XDL_MERGE_FAVOR_UNION;

  return ll_xdl_merge(drv_unused, result, path,

          orig, orig_name, src1, name1, src2, name2,

          &o, marker_size);

}

#define LL_BINARY_MERGE 0

#define LL_TEXT_MERGE 1

#define LL_UNION_MERGE 2

static struct ll_merge_driver ll_merge_drv[] = {

  { "binary", "built-in binary merge", ll_binary_merge },

  { "text", "built-in 3-way text merge", ll_xdl_merge },

  { "union", "built-in union merge", ll_union_merge },

};

static struct tempfile *create_temp(mmfile_t *src)

{

  struct tempfile *t = xmks_tempfile(".merge_file_XXXXXX");

  if (write_in_full(t->fd, src->ptr, src->size) < 0)

    die_errno(_("unable to write %s"), get_tempfile_path(t));

  if (close_tempfile_gently(t) < 0)

    die_errno(_("unable to close %s"), get_tempfile_path(t));

  return t;

}

static const char *temp_path_basename(struct tempfile *t)

{

  /*

   * basename() takes a non-const pointer because it can

   * modify the input string to remove trailing directory

   * separators. We know that we don't have any because

   * this is a clean path generated from our vanilla

   * tempfile template.

   *

   * So casting away the const here is safe, albeit gross.

   */

  return basename((char *)get_tempfile_path(t));

}

/*

 * User defined low-level merge driver support.

 */

static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,

      mmfile_t *result,

      const char *path,

      mmfile_t *orig, const char *orig_name,

      mmfile_t *src1, const char *name1,

      mmfile_t *src2, const char *name2,

      const struct ll_merge_options *opts,

      int marker_size)

{

  struct tempfile *tmp_o, *tmp_a, *tmp_b;

  struct strbuf cmd = STRBUF_INIT;

  const char *format = fn->cmdline;

  struct child_process child = CHILD_PROCESS_INIT;

  int status;

  enum ll_merge_result ret;

  assert(opts);

  if (!fn->cmdline)

    die("custom merge driver %s lacks command line.", fn->name);

  result->ptr = NULL;

  result->size = 0;

  tmp_o = create_temp(orig);

  tmp_a = create_temp(src1);

  tmp_b = create_temp(src2);

  while (strbuf_expand_step(&cmd, &format)) {

    if (skip_prefix(format, "%", &format))

      strbuf_addch(&cmd, '%');

    else if (skip_prefix(format, "O", &format))

      strbuf_addstr(&cmd, temp_path_basename(tmp_o));

    else if (skip_prefix(format, "A", &format))

      strbuf_addstr(&cmd, temp_path_basename(tmp_a));

    else if (skip_prefix(format, "B", &format))

      strbuf_addstr(&cmd, temp_path_basename(tmp_b));

    else if (skip_prefix(format, "L", &format))

      strbuf_addf(&cmd, "%d", marker_size);

    else if (skip_prefix(format, "P", &format))

      sq_quote_buf(&cmd, path);

    else if (skip_prefix(format, "S", &format))

      sq_quote_buf(&cmd, orig_name ? orig_name : "");

    else if (skip_prefix(format, "X", &format))

      sq_quote_buf(&cmd, name1 ? name1 : "");

    else if (skip_prefix(format, "Y", &format))

      sq_quote_buf(&cmd, name2 ? name2 : "");

    else

      strbuf_addch(&cmd, '%');

  }

  child.use_shell = 1;

  strvec_push(&child.args, cmd.buf);

  status = run_command(&child);

  if (!status)

    ret = LL_MERGE_OK;

  else if (status <= 128)

    ret = LL_MERGE_CONFLICT;

  else

    /* died due to a signal: WTERMSIG(status) + 128 */

    ret = LL_MERGE_ERROR;

  if (read_mmfile(result, temp_path_basename(tmp_a)) < 0)

    ret = LL_MERGE_ERROR;

  delete_tempfile(&tmp_o);

  delete_tempfile(&tmp_a);

  delete_tempfile(&tmp_b);

  strbuf_release(&cmd);

  return ret;

}

/*

 * merge.default and merge.driver configuration items

 */

static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;

static char *default_ll_merge;

static int read_merge_config(const char *var, const char *value,

           const struct config_context *ctx UNUSED,

           void *cb UNUSED)

{

  struct ll_merge_driver *fn;

  const char *key, *name;

  size_t namelen;

  if (!strcmp(var, "merge.default"))

    return git_config_string(&default_ll_merge, var, value);

  /*

   * We are not interested in anything but "merge.<name>.variable";

   * especially, we do not want to look at variables such as

   * "merge.summary", "merge.tool", and "merge.verbosity".

   */

  if (parse_config_key(var, "merge", &name, &namelen, &key) < 0 || !name)

    return 0;

  /*

   * Find existing one as we might be processing merge.<name>.var2

   * after seeing merge.<name>.var1.

   */

  for (fn = ll_user_merge; fn; fn = fn->next)

    if (!xstrncmpz(fn->name, name, namelen))

      break;

  if (!fn) {

    CALLOC_ARRAY(fn, 1);

    fn->name = xmemdupz(name, namelen);

    fn->fn = ll_ext_merge;

    *ll_user_merge_tail = fn;

    ll_user_merge_tail = &(fn->next);

  }

  if (!strcmp("name", key)) {

    /*

     * The description is leaking, but that's okay as we want to

     * keep around the merge drivers anyway.

     */

    return git_config_string((char **) &fn->description, var, value);

  }

  if (!strcmp("driver", key)) {

    if (!value)

      return config_error_nonbool(var);

    /*

     * merge.<name>.driver specifies the command line:

     *

     *  command-line

     *

     * The command-line will be interpolated with the following

     * tokens and is given to the shell:

     *

     *    %O - temporary file name for the merge base.

     *    %A - temporary file name for our version.

     *    %B - temporary file name for the other branches' version.

     *    %L - conflict marker length

     *    %P - the original path (safely quoted for the shell)

     *    %S - the revision for the merge base

     *    %X - the revision for our version

     *    %Y - the revision for their version

     *

     * If the file is not named identically in all versions, then each

     * revision is joined with the corresponding path, separated by a colon.

     * The external merge driver should write the results in the

     * file named by %A, and signal that it has done with zero exit

     * status.

     */

    fn->cmdline = xstrdup(value);

    return 0;

  }

  if (!strcmp("recursive", key))

    return git_config_string(&fn->recursive, var, value);

  return 0;

}

static void initialize_ll_merge(void)

{

  if (ll_user_merge_tail)

    return;

  ll_user_merge_tail = &ll_user_merge;

  repo_config(the_repository, read_merge_config, NULL);

}

static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)

{

  struct ll_merge_driver *fn;

  const char *name;

  int i;

  initialize_ll_merge();

  if (ATTR_TRUE(merge_attr))

    return &ll_merge_drv[LL_TEXT_MERGE];

  else if (ATTR_FALSE(merge_attr))

    return &ll_merge_drv[LL_BINARY_MERGE];

  else if (ATTR_UNSET(merge_attr)) {

    if (!default_ll_merge)

      return &ll_merge_drv[LL_TEXT_MERGE];

    else

      name = default_ll_merge;

  }

  else

    name = merge_attr;

  for (fn = ll_user_merge; fn; fn = fn->next)

    if (!strcmp(fn->name, name))

      return fn;

  for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)

    if (!strcmp(ll_merge_drv[i].name, name))

      return &ll_merge_drv[i];

  /* default to the 3-way */

  return &ll_merge_drv[LL_TEXT_MERGE];

}

static void normalize_file(mmfile_t *mm, const char *path, struct index_state *istate)

{

  struct strbuf strbuf = STRBUF_INIT;

  if (renormalize_buffer(istate, path, mm->ptr, mm->size, &strbuf)) {

    free(mm->ptr);

    mm->size = strbuf.len;

    mm->ptr = strbuf_detach(&strbuf, NULL);

  }

}

enum ll_merge_result ll_merge(mmfile_t *result_buf,

       const char *path,

       mmfile_t *ancestor, const char *ancestor_label,

       mmfile_t *ours, const char *our_label,

       mmfile_t *theirs, const char *their_label,

       struct index_state *istate,

       const struct ll_merge_options *opts)

{

  struct attr_check *check = load_merge_attributes();

  static const struct ll_merge_options default_opts = LL_MERGE_OPTIONS_INIT;

  const char *ll_driver_name = NULL;

  int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

  const struct ll_merge_driver *driver;

  if (!opts)

    opts = &default_opts;

  if (opts->renormalize) {

    normalize_file(ancestor, path, istate);

    normalize_file(ours, path, istate);

    normalize_file(theirs, path, istate);

  }

  git_check_attr(istate, path, check);

  ll_driver_name = check->items[0].value;

  if (check->items[1].value) {

    if (strtol_i(check->items[1].value, 10, &marker_size)) {

      marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

      warning(_("invalid marker-size '%s', expecting an integer"), check->items[1].value);

    }

    if (marker_size <= 0)

      marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

  }

  driver = find_ll_merge_driver(ll_driver_name);

  if (opts->virtual_ancestor) {

    if (driver->recursive)

      driver = find_ll_merge_driver(driver->recursive);

  }

  if (opts->extra_marker_size) {

    marker_size += opts->extra_marker_size;

  }

  return driver->fn(driver, result_buf, path, ancestor, ancestor_label,

        ours, our_label, theirs, their_label,

        opts, marker_size);

}

int ll_merge_marker_size(struct index_state *istate, const char *path)

{

  static struct attr_check *check;

  int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

  if (!check)

    check = attr_check_initl("conflict-marker-size", NULL);

  git_check_attr(istate, path, check);

  if (check->items[0].value) {

    if (strtol_i(check->items[0].value, 10, &marker_size)) {

      marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

      warning(_("invalid marker-size '%s', expecting an integer"), check->items[0].value);

    }

    if (marker_size <= 0)

      marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

  }

  return marker_size;

}

int is_conflict_marker_line(const char *line, unsigned long len, int marker_size)

{

  char firstchar;

  int cnt;

  if (len < marker_size + 1)

    return 0;

  firstchar = line[0];

  switch (firstchar) {

  case '=': case '>': case '<': case '|':

    break;

  default:

    return 0;

  }

  for (cnt = 1; cnt < marker_size; cnt++) {

    if (line[cnt] != firstchar)

      return 0;

  }

  if (((firstchar == '<') || (firstchar == '>')) &&

      line[marker_size] != ' ')

    return 0;

  if (!isspace((unsigned char)line[marker_size]))

    return 0;

  return firstchar;

}

int has_conflict_markers(struct index_state *istate, const char *path)

{

  FILE *f;

  struct strbuf sb = STRBUF_INIT;

  int marker_size = ll_merge_marker_size(istate, path);

  int has_markers = 0;

  f = fopen(path, "r");

  if (!f)

    return 0;

  while (strbuf_getwholeline(&sb, f, '\n') != EOF) {

    if (is_conflict_marker_line(sb.buf, sb.len, marker_size)) {

      has_markers = 1;

      break;

    }

    if (buffer_is_binary(sb.buf,

             ULONG_MAX <= sb.len ? ULONG_MAX : sb.len))

      break;

  }

  fclose(f);

  strbuf_release(&sb);

  return has_markers;

}