from __future__ import absolute_import

import collections

import os

import sqlite3

import pygit2

from mercurial.i18n import _

from mercurial import (

    encoding,

    error,

    node as nodemod,

    pycompat,

)

from . import gitutil

_CURRENT_SCHEMA_VERSION = 1

_SCHEMA = (

    """

CREATE TABLE refs (

  -- node and name are unique together. There may be more than one name for

  -- a given node, and there may be no name at all for a given node (in the

  -- case of an anonymous hg head).

  node TEXT NOT NULL,

  name TEXT

);

-- The "possible heads" of the repository, which we use to figure out

-- if we need to re-walk the changelog.

CREATE TABLE possible_heads (

  node TEXT NOT NULL

);

-- The topological heads of the changelog, which hg depends on.

CREATE TABLE heads (

  node TEXT NOT NULL

);

-- A total ordering of the changelog

CREATE TABLE changelog (

  rev INTEGER NOT NULL PRIMARY KEY,

  node TEXT NOT NULL,

  p1 TEXT,

  p2 TEXT

);

CREATE UNIQUE INDEX changelog_node_idx ON changelog(node);

CREATE UNIQUE INDEX changelog_node_rev_idx ON changelog(rev, node);

-- Changed files for each commit, which lets us dynamically build

-- filelogs.

CREATE TABLE changedfiles (

  node TEXT NOT NULL,

  filename TEXT NOT NULL,

  -- 40 zeroes for deletions

  filenode TEXT NOT NULL,

-- to handle filelog parentage:

  p1node TEXT,

  p1filenode TEXT,

  p2node TEXT,

  p2filenode TEXT

);

CREATE INDEX changedfiles_nodes_idx

  ON changedfiles(node);

PRAGMA user_version=%d

"""

    % _CURRENT_SCHEMA_VERSION

)

def _createdb(path):

    # print('open db', path)

    # import traceback

    # traceback.print_stack()

    db = sqlite3.connect(encoding.strfromlocal(path))

    db.text_factory = bytes

    res = db.execute('PRAGMA user_version').fetchone()[0]

    # New database.

    if res == 0:

        for statement in _SCHEMA.split(';'):

            db.execute(statement.strip())

        db.commit()

    elif res == _CURRENT_SCHEMA_VERSION:

        pass

    else:

        raise error.Abort(_(b'sqlite database has unrecognized version'))

    db.execute('PRAGMA journal_mode=WAL')

    return db

_OUR_ORDER = (

    pygit2.GIT_SORT_TOPOLOGICAL | pygit2.GIT_SORT_TIME | pygit2.GIT_SORT_REVERSE

)

_DIFF_FLAGS = 1 << 21  # GIT_DIFF_FORCE_BINARY, which isn't exposed by pygit2

def _find_nearest_ancestor_introducing_node(

    db, gitrepo, file_path, walk_start, filenode

):

    """Find the nearest ancestor that introduces a file node.

    Args:

      db: a handle to our sqlite database.

      gitrepo: A pygit2.Repository instance.

      file_path: the path of a file in the repo

      walk_start: a pygit2.Oid that is a commit where we should start walking

                  for our nearest ancestor.

    Returns:

      A hexlified SHA that is the commit ID of the next-nearest parent.

    """

    assert isinstance(file_path, str), 'file_path must be str, got %r' % type(

        file_path

    )

    assert isinstance(filenode, str), 'filenode must be str, got %r' % type(

        filenode

    )

    parent_options = {

        row[0].decode('ascii')

        for row in db.execute(

            'SELECT node FROM changedfiles '

            'WHERE filename = ? AND filenode = ?',

            (file_path, filenode),

        )

    }

    inner_walker = gitrepo.walk(walk_start, _OUR_ORDER)

    for w in inner_walker:

        if w.id.hex in parent_options:

            return w.id.hex

    raise error.ProgrammingError(

        'Unable to find introducing commit for %s node %s from %s',

        (file_path, filenode, walk_start),

    )

def fill_in_filelog(gitrepo, db, startcommit, path, startfilenode):

    """Given a starting commit and path, fill in a filelog's parent pointers.

    Args:

      gitrepo: a pygit2.Repository

      db: a handle to our sqlite database

      startcommit: a hexlified node id for the commit to start at

      path: the path of the file whose parent pointers we should fill in.

      filenode: the hexlified node id of the file at startcommit

    TODO: make filenode optional

    """

    assert isinstance(

        startcommit, str

    ), 'startcommit must be str, got %r' % type(startcommit)

    assert isinstance(

        startfilenode, str

    ), 'startfilenode must be str, got %r' % type(startfilenode)

    visit = collections.deque([(startcommit, startfilenode)])

    while visit:

        cnode, filenode = visit.popleft()

        commit = gitrepo[cnode]

        parents = []

        for parent in commit.parents:

            t = parent.tree

            for comp in path.split('/'):

                try:

                    t = gitrepo[t[comp].id]

                except KeyError:

                    break

            else:

                introducer = _find_nearest_ancestor_introducing_node(

                    db, gitrepo, path, parent.id, t.id.hex

                )

                parents.append((introducer, t.id.hex))

        p1node = p1fnode = p2node = p2fnode = gitutil.nullgit

        for par, parfnode in parents:

            found = int(

                db.execute(

                    'SELECT COUNT(*) FROM changedfiles WHERE '

                    'node = ? AND filename = ? AND filenode = ? AND '

                    'p1node NOT NULL',

                    (par, path, parfnode),

                ).fetchone()[0]

            )

            if found == 0:

                assert par is not None

                visit.append((par, parfnode))

        if parents:

            p1node, p1fnode = parents[0]

        if len(parents) == 2:

            p2node, p2fnode = parents[1]

        if len(parents) > 2:

            raise error.ProgrammingError(

                b"git support can't handle octopus merges"

            )

        db.execute(

            'UPDATE changedfiles SET '

            'p1node = ?, p1filenode = ?, p2node = ?, p2filenode = ? '

            'WHERE node = ? AND filename = ? AND filenode = ?',

            (p1node, p1fnode, p2node, p2fnode, commit.id.hex, path, filenode),

        )

    db.commit()

def _index_repo(gitrepo, db, progress_factory=lambda *args, **kwargs: None):

    # Identify all references so we can tell the walker to visit all of them.

    all_refs = gitrepo.listall_references()

    possible_heads = set()

    prog = progress_factory(b'refs')

    for pos, ref in enumerate(all_refs):

        if prog is not None:

            prog.update(pos)

        if not (

            ref.startswith('refs/heads/')  # local branch

            or ref.startswith('refs/tags/')  # tag

            or ref.startswith('refs/remotes/')  # remote branch

            or ref.startswith('refs/hg/')  # from this extension

        ):

            continue

        try:

            start = gitrepo.lookup_reference(ref).peel(pygit2.GIT_OBJ_COMMIT)

        except ValueError:

            # No commit to be found, so we don't care for hg's purposes.

            continue

        possible_heads.add(start.id)

    # Optimization: if the list of heads hasn't changed, don't

    # reindex, the changelog. This doesn't matter on small

    # repositories, but on even moderately deep histories (eg cpython)

    # this is a very important performance win.

    #

    # TODO: we should figure out how to incrementally index history

    # (preferably by detecting rewinds!) so that we don't have to do a

    # full changelog walk every time a new commit is created.

    cache_heads = {x[0] for x in db.execute('SELECT node FROM possible_heads')}

    walker = None

    cur_cache_heads = {h.hex for h in possible_heads}

    if cur_cache_heads == cache_heads:

        return

    for start in possible_heads:

        if walker is None:

            walker = gitrepo.walk(start, _OUR_ORDER)

        else:

            walker.push(start)

    # Empty out the existing changelog. Even for large-ish histories

    # we can do the top-level "walk all the commits" dance very

    # quickly as long as we don't need to figure out the changed files

    # list.

    db.execute('DELETE FROM changelog')

    if prog is not None:

        prog.complete()

    prog = progress_factory(b'commits')

    # This walker is sure to visit all the revisions in history, but

    # only once.

    for pos, commit in enumerate(walker):

        if prog is not None:

            prog.update(pos)

        p1 = p2 = nodemod.nullhex

        if len(commit.parents) > 2:

            raise error.ProgrammingError(

                (

                    b"git support can't handle octopus merges, "

                    b"found a commit with %d parents :("

                )

                % len(commit.parents)

            )

        if commit.parents:

            p1 = commit.parents[0].id.hex

        if len(commit.parents) == 2:

            p2 = commit.parents[1].id.hex

        db.execute(

            'INSERT INTO changelog (rev, node, p1, p2) VALUES(?, ?, ?, ?)',

            (pos, commit.id.hex, p1, p2),

        )

        num_changedfiles = db.execute(

            "SELECT COUNT(*) from changedfiles WHERE node = ?",

            (commit.id.hex,),

        ).fetchone()[0]

        if not num_changedfiles:

            files = {}

            # I *think* we only need to check p1 for changed files

            # (and therefore linkrevs), because any node that would

            # actually have this commit as a linkrev would be

            # completely new in this rev.

            p1 = commit.parents[0].id.hex if commit.parents else None

            if p1 is not None:

                patchgen = gitrepo.diff(p1, commit.id.hex, flags=_DIFF_FLAGS)

            else:

                patchgen = commit.tree.diff_to_tree(

                    swap=True, flags=_DIFF_FLAGS

                )

            new_files = (p.delta.new_file for p in patchgen)

            files = {

                nf.path: nf.id.hex

                for nf in new_files

                if nf.id.raw != nodemod.nullid

            }

            for p, n in files.items():

                # We intentionally set NULLs for any file parentage

                # information so it'll get demand-computed later. We

                # used to do it right here, and it was _very_ slow.

                db.execute(

                    'INSERT INTO changedfiles ('

                    'node, filename, filenode, p1node, p1filenode, p2node, '

                    'p2filenode) VALUES(?, ?, ?, ?, ?, ?, ?)',

                    (commit.id.hex, p, n, None, None, None, None),

                )

    db.execute('DELETE FROM heads')

    db.execute('DELETE FROM possible_heads')

    for hid in possible_heads:

        h = hid.hex

        db.execute('INSERT INTO possible_heads (node) VALUES(?)', (h,))

        haschild = db.execute(

            'SELECT COUNT(*) FROM changelog WHERE p1 = ? OR p2 = ?', (h, h)

        ).fetchone()[0]

        if not haschild:

            db.execute('INSERT INTO heads (node) VALUES(?)', (h,))

    db.commit()

    if prog is not None:

        prog.complete()

def get_index(gitrepo, progress_factory=lambda *args, **kwargs: None):

    cachepath = os.path.join(

        pycompat.fsencode(gitrepo.path), b'..', b'.hg', b'cache'

    )

    if not os.path.exists(cachepath):

        os.makedirs(cachepath)

    dbpath = os.path.join(cachepath, b'git-commits.sqlite')

    db = _createdb(dbpath)

    # TODO check against gitrepo heads before doing a full index

    # TODO thread a ui.progress call into this layer

    _index_repo(gitrepo, db, progress_factory)

    return db