"""
fuse.py — FUSE filesystem layer for Trove, backed by pyfuse3 + trio.

Blob objects are exposed as regular files.
Tree objects are exposed as directories.

Inode numbers map 1:1 to Trove object IDs (NODE_ROOT_ID == pyfuse3 root inode == 1).

Entry point: serve(trove, mountpoint)
"""

import errno
import os
import stat
import time

import pyfuse3
import trio

from trovedb.trove import Trove, Note, Tree as TroveTree, TreeNote, Blob as TroveBlob


class TroveFuseOps(pyfuse3.Operations):

    enable_writeback_cache = False

    def __init__(self, trove: Trove):
        super().__init__()
        self._trove = trove

    # ------------------------------------------------------------------
    # Helpers
    # ------------------------------------------------------------------

    def _note_or_error(self, inode: int):
        note = self._trove.get_raw_note(inode)
        if note is None:
            raise pyfuse3.FUSEError(errno.ENOENT)
        return note

    def _make_attr(self, inode: int, is_tree: bool, size: int = 0) -> pyfuse3.EntryAttributes:
        attr = pyfuse3.EntryAttributes()
        attr.st_ino = pyfuse3.InodeT(inode)
        attr.st_nlink = 1
        attr.st_uid = os.getuid()
        attr.st_gid = os.getgid()
        now_ns = int(time.time() * 1e9)
        attr.st_atime_ns = now_ns
        attr.st_mtime_ns = now_ns
        attr.st_ctime_ns = now_ns
        attr.generation = 0
        attr.entry_timeout = 5.0
        attr.attr_timeout = 5.0
        if is_tree:
            attr.st_mode = stat.S_IFDIR | 0o755
            attr.st_size = 0
            attr.st_blksize = 512
            attr.st_blocks = 0
        else:
            attr.st_mode = stat.S_IFREG | 0o644
            attr.st_size = size
            attr.st_blksize = 512
            attr.st_blocks = (size + 511) // 512
        return attr

    def _attr_for_note(self, note: Note) -> pyfuse3.EntryAttributes:
        size = 0
        is_tree = True
        if isinstance(note, TroveBlob):
            size = len(note.read())
            is_tree = False
        return self._make_attr(note.object_id, is_tree, size)

    # ------------------------------------------------------------------
    # Stat / lookup
    # ------------------------------------------------------------------

    async def getattr(self, inode: int, ctx=None) -> pyfuse3.EntryAttributes:
        note = self._note_or_error(inode)
        return self._attr_for_note(note)

    async def lookup(self, parent_inode: int, name: bytes, ctx=None) -> pyfuse3.EntryAttributes:
        parent = self._note_or_error(parent_inode)
        if not isinstance(parent, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        entries = parent.list()
        name_str = name.decode()
        if name_str not in entries:
            raise pyfuse3.FUSEError(errno.ENOENT)
        child = self._trove.get_raw_note(entries[name_str])
        if child is None:
            raise pyfuse3.FUSEError(errno.ENOENT)
        return self._attr_for_note(child)

    async def setattr(self, inode: int, attr, fields, fh, ctx) -> pyfuse3.EntryAttributes:
        note = self._note_or_error(inode)
        if fields.update_size and not isinstance(note, TroveTree):
            current = note.read()
            new_size = attr.st_size
            if new_size < len(current):
                note.write(current[:new_size])
            elif new_size > len(current):
                note.write(current + b"\x00" * (new_size - len(current)))
        return self._attr_for_note(note)

    async def forget(self, inode_list) -> None:
        pass

    # ------------------------------------------------------------------
    # Directory ops
    # ------------------------------------------------------------------

    async def opendir(self, inode: int, ctx) -> pyfuse3.FileHandleT:
        note = self._note_or_error(inode)
        if not isinstance(note, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        return pyfuse3.FileHandleT(inode)

    async def readdir(self, fh: int, start_id: int, token) -> None:
        note = self._note_or_error(fh)
        if not isinstance(note, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        entries = list(note.list().items())  # [(name, object_id), ...]
        for idx, (name, child_id) in enumerate(entries):
            if idx < start_id:
                continue
            child = self._trove.get_raw_note(child_id)
            if child is None:
                continue
            attr = self._attr_for_note(child)
            if not pyfuse3.readdir_reply(token, name.encode(), attr, idx + 1):
                break

    async def releasedir(self, fh: int) -> None:
        pass

    async def mkdir(self, parent_inode: int, name: bytes, mode: int, ctx) -> pyfuse3.EntryAttributes:
        parent = self._note_or_error(parent_inode)
        if not isinstance(parent, TreeNote):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        name_str = name.decode()
        if name_str in parent.list():
            raise pyfuse3.FUSEError(errno.EEXIST)
        new_tree: TreeNote = parent.mkdir(name_str)
        return self._make_attr(new_tree.object_id, True, 0)

    async def rmdir(self, parent_inode: int, name: bytes, ctx) -> None:
        parent = self._note_or_error(parent_inode)
        if not isinstance(parent, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        name_str = name.decode()
        entries = parent.list()
        if name_str not in entries:
            raise pyfuse3.FUSEError(errno.ENOENT)
        child = self._trove.get_raw_note(entries[name_str])
        if child is None:
            raise pyfuse3.FUSEError(errno.ENOENT)
        if not isinstance(child, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        if child.list():
            raise pyfuse3.FUSEError(errno.ENOTEMPTY)
        parent.unlink(name_str)

    # ------------------------------------------------------------------
    # File ops
    # ------------------------------------------------------------------

    async def open(self, inode: int, flags, ctx) -> pyfuse3.FileInfo:
        note = self._note_or_error(inode)
        if isinstance(note, TroveTree):
            raise pyfuse3.FUSEError(errno.EISDIR)
        return pyfuse3.FileInfo(fh=pyfuse3.FileHandleT(inode))

    async def create(self, parent_inode: int, name: bytes, mode: int, flags, ctx) -> tuple:
        parent = self._note_or_error(parent_inode)
        if not isinstance(parent, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        name_str = name.decode()
        if name_str in parent.list():
            raise pyfuse3.FUSEError(errno.EEXIST)
        blob = self._trove.create_blob(b"")
        parent.link(name_str, blob)
        attr = self._make_attr(blob.object_id, False, 0)
        return pyfuse3.FileInfo(fh=pyfuse3.FileHandleT(blob.object_id)), attr

    async def read(self, fh: int, offset: int, length: int) -> bytes:
        note = self._note_or_error(fh)
        return note.read()[offset:offset + length]

    async def write(self, fh: int, offset: int, data: bytes) -> int:
        note = self._note_or_error(fh)
        existing = note.read()
        if offset > len(existing):
            existing = existing + b"\x00" * (offset - len(existing))
        note.write(existing[:offset] + data + existing[offset + len(data):])
        return len(data)

    async def release(self, fh: int) -> None:
        pass

    async def unlink(self, parent_inode: int, name: bytes, ctx) -> None:
        parent = self._note_or_error(parent_inode)
        if not isinstance(parent, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)
        name_str = name.decode()
        entries = parent.list()
        if name_str not in entries:
            raise pyfuse3.FUSEError(errno.ENOENT)
        child = self._trove.get_raw_note(entries[name_str])
        if child is None:
            raise pyfuse3.FUSEError(errno.ENOENT)
        if isinstance(child, TroveTree):
            raise pyfuse3.FUSEError(errno.EISDIR)
        parent.unlink(name_str)

    async def rename(self, parent_inode_old, name_old, parent_inode_new, name_new, flags, ctx):
        old_parent = self._note_or_error(parent_inode_old)
        new_parent = self._note_or_error(parent_inode_new)
        if not isinstance(old_parent, TroveTree) or not isinstance(new_parent, TroveTree):
            raise pyfuse3.FUSEError(errno.ENOTDIR)

        name_old_str = name_old.decode()
        name_new_str = name_new.decode()

        old_entries = old_parent.list()
        if name_old_str not in old_entries:
            raise pyfuse3.FUSEError(errno.ENOENT)

        child_id = old_entries[name_old_str]
        child = self._trove.get_raw_note(child_id)
        if child is None:
            raise pyfuse3.FUSEError(errno.ENOENT)

        # Remove existing target if present
        new_entries = new_parent.list()
        if name_new_str in new_entries:
            target = self._trove.get_raw_note(new_entries[name_new_str])
            if target is not None and isinstance(target, TroveTree):
                if target.list():
                    raise pyfuse3.FUSEError(errno.ENOTEMPTY)
            new_parent.unlink(name_new_str)

        new_parent.link(name_new_str, child)
        old_parent.unlink(name_old_str)


# ------------------------------------------------------------------
# Serve
# ------------------------------------------------------------------

async def _run(ops: TroveFuseOps, mountpoint: str) -> None:
    options = set(pyfuse3.default_options)
    options.add("fsname=trove")
    pyfuse3.init(ops, mountpoint, options)
    try:
        await pyfuse3.main()
    finally:
        pyfuse3.close()


def serve(trove: Trove, mountpoint: str) -> None:
    """
    Mount a Trove store at mountpoint and serve until KeyboardInterrupt.
    Runs a trio event loop internally.
    """
    ops = TroveFuseOps(trove)
    try:
        trio.run(_run, ops, mountpoint)
    except KeyboardInterrupt:
        pass