import struct

from mercurial.node import (

    hex,

    sha1nodeconstants,

)

from mercurial import (

    util,

)

from mercurial.utils import hashutil

from . import (

    basepack,

    constants,

    shallowutil,

)

# (filename hash, offset, size)

INDEXFORMAT2 = b'!20sQQII'

INDEXENTRYLENGTH2 = struct.calcsize(INDEXFORMAT2)

NODELENGTH = 20

NODEINDEXFORMAT = b'!20sQ'

NODEINDEXENTRYLENGTH = struct.calcsize(NODEINDEXFORMAT)

# (node, p1, p2, linknode)

PACKFORMAT = b"!20s20s20s20sH"

PACKENTRYLENGTH = 82

ENTRYCOUNTSIZE = 4

INDEXSUFFIX = b'.histidx'

PACKSUFFIX = b'.histpack'

ANC_NODE = 0

ANC_P1NODE = 1

ANC_P2NODE = 2

ANC_LINKNODE = 3

ANC_COPYFROM = 4

class historypackstore(basepack.basepackstore):

    INDEXSUFFIX = INDEXSUFFIX

    PACKSUFFIX = PACKSUFFIX

    def getpack(self, path):

        return historypack(path)

    def getancestors(self, name, node, known=None):

        for pack in self.packs:

            try:

                return pack.getancestors(name, node, known=known)

            except KeyError:

                pass

        for pack in self.refresh():

            try:

                return pack.getancestors(name, node, known=known)

            except KeyError:

                pass

        raise KeyError((name, node))

    def getnodeinfo(self, name, node):

        for pack in self.packs:

            try:

                return pack.getnodeinfo(name, node)

            except KeyError:

                pass

        for pack in self.refresh():

            try:

                return pack.getnodeinfo(name, node)

            except KeyError:

                pass

        raise KeyError((name, node))

    def add(self, filename, node, p1, p2, linknode, copyfrom):

        raise RuntimeError(

            b"cannot add to historypackstore (%s:%s)" % (filename, hex(node))

        )

class historypack(basepack.basepack):

    INDEXSUFFIX = INDEXSUFFIX

    PACKSUFFIX = PACKSUFFIX

    SUPPORTED_VERSIONS = [2]

    def __init__(self, path):

        super(historypack, self).__init__(path)

        self.INDEXFORMAT = INDEXFORMAT2

        self.INDEXENTRYLENGTH = INDEXENTRYLENGTH2

    def getmissing(self, keys):

        missing = []

        for name, node in keys:

            try:

                self._findnode(name, node)

            except KeyError:

                missing.append((name, node))

        return missing

    def getancestors(self, name, node, known=None):

        """Returns as many ancestors as we're aware of.

        return value: {

           node: (p1, p2, linknode, copyfrom),

           ...

        }

        """

        if known and node in known:

            return []

        ancestors = self._getancestors(name, node, known=known)

        results = {}

        for ancnode, p1, p2, linknode, copyfrom in ancestors:

            results[ancnode] = (p1, p2, linknode, copyfrom)

        if not results:

            raise KeyError((name, node))

        return results

    def getnodeinfo(self, name, node):

        # Drop the node from the tuple before returning, since the result should

        # just be (p1, p2, linknode, copyfrom)

        return self._findnode(name, node)[1:]

    def _getancestors(self, name, node, known=None):

        if known is None:

            known = set()

        section = self._findsection(name)

        filename, offset, size, nodeindexoffset, nodeindexsize = section

        pending = {node}

        o = 0

        while o < size:

            if not pending:

                break

            entry, copyfrom = self._readentry(offset + o)

            o += PACKENTRYLENGTH

            if copyfrom:

                o += len(copyfrom)

            ancnode = entry[ANC_NODE]

            if ancnode in pending:

                pending.remove(ancnode)

                p1node = entry[ANC_P1NODE]

                p2node = entry[ANC_P2NODE]

                if p1node != sha1nodeconstants.nullid and p1node not in known:

                    pending.add(p1node)

                if p2node != sha1nodeconstants.nullid and p2node not in known:

                    pending.add(p2node)

                yield (ancnode, p1node, p2node, entry[ANC_LINKNODE], copyfrom)

    def _readentry(self, offset):

        data = self._data

        entry = struct.unpack(

            PACKFORMAT, data[offset : offset + PACKENTRYLENGTH]

        )

        copyfrom = None

        copyfromlen = entry[ANC_COPYFROM]

        if copyfromlen != 0:

            offset += PACKENTRYLENGTH

            copyfrom = data[offset : offset + copyfromlen]

        return entry, copyfrom

    def add(self, filename, node, p1, p2, linknode, copyfrom):

        raise RuntimeError(

            b"cannot add to historypack (%s:%s)" % (filename, hex(node))

        )

    def _findnode(self, name, node):

        if self.VERSION == 0:

            ancestors = self._getancestors(name, node)

            for ancnode, p1node, p2node, linknode, copyfrom in ancestors:

                if ancnode == node:

                    return (ancnode, p1node, p2node, linknode, copyfrom)

        else:

            section = self._findsection(name)

            nodeindexoffset, nodeindexsize = section[3:]

            entry = self._bisect(

                node,

                nodeindexoffset,

                nodeindexoffset + nodeindexsize,

                NODEINDEXENTRYLENGTH,

            )

            if entry is not None:

                node, offset = struct.unpack(NODEINDEXFORMAT, entry)

                entry, copyfrom = self._readentry(offset)

                # Drop the copyfromlen from the end of entry, and replace it

                # with the copyfrom string.

                return entry[:4] + (copyfrom,)

        raise KeyError(b"unable to find history for %s:%s" % (name, hex(node)))

    def _findsection(self, name):

        params = self.params

        namehash = hashutil.sha1(name).digest()

        fanoutkey = struct.unpack(

            params.fanoutstruct, namehash[: params.fanoutprefix]

        )[0]

        fanout = self._fanouttable

        start = fanout[fanoutkey] + params.indexstart

        indexend = self._indexend

        for i in range(fanoutkey + 1, params.fanoutcount):

            end = fanout[i] + params.indexstart

            if end != start:

                break

        else:

            end = indexend

        entry = self._bisect(namehash, start, end, self.INDEXENTRYLENGTH)

        if not entry:

            raise KeyError(name)

        rawentry = struct.unpack(self.INDEXFORMAT, entry)

        x, offset, size, nodeindexoffset, nodeindexsize = rawentry

        rawnamelen = self._index[

            nodeindexoffset : nodeindexoffset + constants.FILENAMESIZE

        ]

        actualnamelen = struct.unpack(b'!H', rawnamelen)[0]

        nodeindexoffset += constants.FILENAMESIZE

        actualname = self._index[

            nodeindexoffset : nodeindexoffset + actualnamelen

        ]

        if actualname != name:

            raise KeyError(

                b"found file name %s when looking for %s" % (actualname, name)

            )

        nodeindexoffset += actualnamelen

        filenamelength = struct.unpack(

            b'!H', self._data[offset : offset + constants.FILENAMESIZE]

        )[0]

        offset += constants.FILENAMESIZE

        actualname = self._data[offset : offset + filenamelength]

        offset += filenamelength

        if name != actualname:

            raise KeyError(

                b"found file name %s when looking for %s" % (actualname, name)

            )

        # Skip entry list size

        offset += ENTRYCOUNTSIZE

        nodelistoffset = offset

        nodelistsize = (

            size - constants.FILENAMESIZE - filenamelength - ENTRYCOUNTSIZE

        )

        return (

            name,

            nodelistoffset,

            nodelistsize,

            nodeindexoffset,

            nodeindexsize,

        )

    def _bisect(self, node, start, end, entrylen):

        # Bisect between start and end to find node

        origstart = start

        startnode = self._index[start : start + NODELENGTH]

        endnode = self._index[end : end + NODELENGTH]

        if startnode == node:

            return self._index[start : start + entrylen]

        elif endnode == node:

            return self._index[end : end + entrylen]

        else:

            while start < end - entrylen:

                mid = start + (end - start) // 2

                mid = mid - ((mid - origstart) % entrylen)

                midnode = self._index[mid : mid + NODELENGTH]

                if midnode == node:

                    return self._index[mid : mid + entrylen]

                if node > midnode:

                    start = mid

                elif node < midnode:

                    end = mid

        return None

    def markledger(self, ledger, options=None):

        for filename, node in self:

            ledger.markhistoryentry(self, filename, node)

    def cleanup(self, ledger):

        entries = ledger.sources.get(self, [])

        allkeys = set(self)

        repackedkeys = {

            (e.filename, e.node) for e in entries if e.historyrepacked

        }

        if len(allkeys - repackedkeys) == 0:

            if self.path not in ledger.created:

                util.unlinkpath(self.indexpath, ignoremissing=True)

                util.unlinkpath(self.packpath, ignoremissing=True)

    def __iter__(self):

        for f, n, x, x, x, x in self.iterentries():

            yield f, n

    def iterentries(self):

        # Start at 1 to skip the header

        offset = 1

        while offset < self.datasize:

            data = self._data

            # <2 byte len> + <filename>

            filenamelen = struct.unpack(

                b'!H', data[offset : offset + constants.FILENAMESIZE]

            )[0]

            offset += constants.FILENAMESIZE

            filename = data[offset : offset + filenamelen]

            offset += filenamelen

            revcount = struct.unpack(

                b'!I', data[offset : offset + ENTRYCOUNTSIZE]

            )[0]

            offset += ENTRYCOUNTSIZE

            for i in range(revcount):

                entry = struct.unpack(

                    PACKFORMAT, data[offset : offset + PACKENTRYLENGTH]

                )

                offset += PACKENTRYLENGTH

                copyfrom = data[offset : offset + entry[ANC_COPYFROM]]

                offset += entry[ANC_COPYFROM]

                yield (

                    filename,

                    entry[ANC_NODE],

                    entry[ANC_P1NODE],

                    entry[ANC_P2NODE],

                    entry[ANC_LINKNODE],

                    copyfrom,

                )

                self._pagedin += PACKENTRYLENGTH

            # If we've read a lot of data from the mmap, free some memory.

            self.freememory()

class mutablehistorypack(basepack.mutablebasepack):

    """A class for constructing and serializing a histpack file and index.

    A history pack is a pair of files that contain the revision history for

    various file revisions in Mercurial. It contains only revision history (like

    parent pointers and linknodes), not any revision content information.

    It consists of two files, with the following format:

    .histpack

        The pack itself is a series of file revisions with some basic header

        information on each.

        datapack = <version: 1 byte>

                   [<filesection>,...]

        filesection = <filename len: 2 byte unsigned int>

                      <filename>

                      <revision count: 4 byte unsigned int>

                      [<revision>,...]

        revision = <node: 20 byte>

                   <p1node: 20 byte>

                   <p2node: 20 byte>

                   <linknode: 20 byte>

                   <copyfromlen: 2 byte>

                   <copyfrom>

        The revisions within each filesection are stored in topological order

        (newest first). If a given entry has a parent from another file (a copy)

        then p1node is the node from the other file, and copyfrom is the

        filepath of the other file.

    .histidx

        The index file provides a mapping from filename to the file section in

        the histpack. In V1 it also contains sub-indexes for specific nodes

        within each file. It consists of three parts, the fanout, the file index

        and the node indexes.

        The file index is a list of index entries, sorted by filename hash (one

        per file section in the pack). Each entry has:

        - node (The 20 byte hash of the filename)

        - pack entry offset (The location of this file section in the histpack)

        - pack content size (The on-disk length of this file section's pack

                             data)

        - node index offset (The location of the file's node index in the index

                             file) [1]

        - node index size (the on-disk length of this file's node index) [1]

        The fanout is a quick lookup table to reduce the number of steps for

        bisecting the index. It is a series of 4 byte pointers to positions

        within the index. It has 2^16 entries, which corresponds to hash

        prefixes [00, 01, 02,..., FD, FE, FF]. Example: the pointer in slot 4F

        points to the index position of the first revision whose node starts

        with 4F. This saves log(2^16) bisect steps.