"""Per-image tag sets (#249): byte-exact storage in the shared vocabulary.

A tag set belongs to one byte record (``media_annotation_bytes``): the
whole-file SHA-256 of one physical file, owned by the file's private locator
(``media_annotation_files``). Callers pass verified facts (digest, size,
``mtime_ns``); nothing here reads the filesystem or resolves an owner through
prompt links, so tagging one image never changes another image, a prompt or a
pair.

Commands run in one ``_pair_transaction`` fenced by the storage epoch, like the
native Library and vocabulary commands. A save is a full replacement guarded
by the set's ``tag_revision``; the identical set sent again (a lost-response
retry, or the current set at its own revision) answers ``replayed: true`` and
writes nothing. ``add_image_tags`` unions into the existing set, keeping the
stored spelling. Names enter the global ``tags`` registry exactly as spelled,
so vocabulary rename, merge and delete carry image links with prompt and pair
links (``PromptDatabase._move_tag_links``).

Cheap reads (spec amendment S1) treat a byte record as *current* only while
the file's present ``(size, mtime_ns)`` equals the record's verified
fingerprint; a file without a current record shows no image tags.
"""

import re
import sqlite3
from contextlib import contextmanager
from typing import Iterator
from uuid import uuid4

from .annotation_schema import (
    BYTES_TABLE,
    FILES_TABLE,
    IMAGE_TAGS_TABLE,
    MAX_LOCATOR_LENGTH,
    METADATA_TABLE,
)
from .library_commands import _UUID, LibraryCommandError, _validate_epoch
from .models import utc_now_iso
from .vocabulary import validate_vocabulary_tag_name

MAX_IMAGE_TAGS = 100
_LOOKUP_CHUNK = 500
_DIGEST = re.compile(r"[0-9a-f]{64}")
_MAX_INT = 2**63 - 1
_MIN_INT = -(2**63)
# Only this module's table constants are interpolated into the SQL below.
_OWNER = f"SELECT id FROM {FILES_TABLE} WHERE locator=?"  # nosec B608
_INSERT_OWNER = (
    f"INSERT INTO {FILES_TABLE}(id,locator,created_at) VALUES(?,?,?)"  # nosec B608
)
_BYTE = (
    f"SELECT id,tag_revision,size,mtime_ns FROM {BYTES_TABLE} "  # nosec B608
    "WHERE file_id=? AND sha256=?"
)
_INSERT_BYTE = (
    f"INSERT INTO {BYTES_TABLE}(id,file_id,sha256,size,mtime_ns,"  # nosec B608
    "verified_at,first_seen_at,tag_revision) VALUES(?,?,?,?,?,?,?,0)"
)
_REFRESH_BYTE = (
    f"UPDATE {BYTES_TABLE} SET size=?,mtime_ns=?,verified_at=? WHERE id=?"  # nosec B608
)
_REFRESH_BY_LOCATOR = (
    f"UPDATE {BYTES_TABLE} SET size=?,mtime_ns=?,verified_at=? "  # nosec B608
    f"WHERE sha256=? AND file_id=({_OWNER})"
)
_BYTE_TAGS = (
    f"SELECT t.name FROM {IMAGE_TAGS_TABLE} mit "  # nosec B608
    "JOIN tags t ON t.id=mit.tag_id WHERE mit.byte_id=? ORDER BY mit.position"
)
_CLEAR_TAGS = f"DELETE FROM {IMAGE_TAGS_TABLE} WHERE byte_id=?"  # nosec B608
_INSERT_TAG = (
    f"INSERT INTO {IMAGE_TAGS_TABLE}(byte_id,tag_id,position) "  # nosec B608
    "VALUES(?,?,?)"
)
_BUMP_REVISION = (
    f"UPDATE {BYTES_TABLE} SET tag_revision=tag_revision+1 WHERE id=?"  # nosec B608
)
_REVISION = f"SELECT tag_revision FROM {BYTES_TABLE} WHERE id=?"  # nosec B608
_BUMP_INDEX = (
    f"UPDATE {METADATA_TABLE} SET "  # nosec B608
    "image_index_revision=image_index_revision+1 WHERE singleton_id=1"
)
_READ = (
    "SELECT b.id,b.tag_revision,"  # nosec B608
    f"(SELECT COUNT(*) FROM {BYTES_TABLE} o WHERE o.file_id=f.id AND o.sha256!=?) "
    f"FROM {FILES_TABLE} f LEFT JOIN {BYTES_TABLE} b "
    "ON b.file_id=f.id AND b.sha256=? WHERE f.locator=?"
)
_FINGERPRINTS = (
    "SELECT f.locator,b.id,b.size,b.mtime_ns,b.verified_at "  # nosec B608
    f"FROM {FILES_TABLE} f JOIN {BYTES_TABLE} b ON b.file_id=f.id "
    "WHERE f.locator IN ({marks})"
)
_TAGS_OF = (
    f"SELECT mit.byte_id,t.name FROM {IMAGE_TAGS_TABLE} mit "  # nosec B608
    "JOIN tags t ON t.id=mit.tag_id WHERE mit.byte_id IN ({marks}) "
    "ORDER BY mit.byte_id,mit.position"
)
_RECORDS = (
    "SELECT f.locator,b.id,b.size,b.mtime_ns,t.name "  # nosec B608
    f"FROM {FILES_TABLE} f JOIN {BYTES_TABLE} b ON b.file_id=f.id "
    f"LEFT JOIN {IMAGE_TAGS_TABLE} mit ON mit.byte_id=b.id "
    "LEFT JOIN tags t ON t.id=mit.tag_id "
    "ORDER BY f.locator,b.first_seen_at,b.id,mit.position"
)


class AnnotationCommandError(LibraryCommandError):
    """An image tag command lost a race or hit the set's bound.

    ``code`` is ``tag-conflict`` (the set changed since it was read) or
    ``tag-limit`` (the union would exceed ``MAX_IMAGE_TAGS``); ``current`` is
    the stored set ``{sha256, tags, tag_revision}`` read inside the
    transaction, so the caller can show it.
    """

    def __init__(self, code: str, epoch: str, current: dict | None = None):
        super().__init__(code, epoch)
        self.current = current


def normalize_image_tags(names: object) -> list[str]:
    """Trim and validate each name, fold case-insensitive repeats, cap at 100.

    The first occurrence keeps its spelling and position. Raises ``ValueError``
    for anything but a list of valid vocabulary names or for more than
    ``MAX_IMAGE_TAGS`` distinct names.
    """
    if not isinstance(names, list):
        raise ValueError("tags must be a list of strings")
    result: list[str] = []
    seen: set[str] = set()
    for value in names:
        name = validate_vocabulary_tag_name(value)
        key = name.casefold()
        if key in seen:
            continue
        seen.add(key)
        result.append(name)
    if len(result) > MAX_IMAGE_TAGS:
        raise ValueError(f"An image can carry at most {MAX_IMAGE_TAGS} tags")
    return result


def _validate_locator(locator: object) -> None:
    if not isinstance(locator, str) or not 0 < len(locator) <= MAX_LOCATOR_LENGTH:
        raise ValueError(
            f"locator must be a nonblank path of at most {MAX_LOCATOR_LENGTH} chars"
        )


def _validate_digest(sha256: object) -> None:
    if not isinstance(sha256, str) or not _DIGEST.fullmatch(sha256):
        raise ValueError("sha256 must be 64 lowercase hexadecimal characters")


def _validate_int(value: object, name: str, minimum: int) -> None:
    if type(value) is not int or not minimum <= value <= _MAX_INT:
        raise ValueError(f"{name} must be an integer not below {minimum}")


def _validate_target(locator: object, sha256: object, size: object, mtime_ns: object):
    _validate_locator(locator)
    _validate_digest(sha256)
    _validate_int(size, "size", 0)
    _validate_int(mtime_ns, "mtime_ns", _MIN_INT)


def _validate_fingerprint(locator: object, fingerprint: object) -> None:
    _validate_locator(locator)
    if (
        not isinstance(fingerprint, tuple)
        or len(fingerprint) != 2
        or any(type(value) is not int for value in fingerprint)
    ):
        raise ValueError("stats must map locators to (size, mtime_ns) integer pairs")


def _new_id() -> str:
    """A canonical UUID; the schema's CHECK lets NULL through, this does not."""
    value = str(uuid4())
    if not _UUID.fullmatch(value):
        raise ValueError("Annotation ids must be canonical UUIDs")
    return value


def _receipt(epoch: str, sha256: str, tags: list, revision: int, replayed: bool):
    return {
        "library_epoch": epoch,
        "sha256": sha256,
        "tags": list(tags),
        "tag_revision": revision,
        "replayed": replayed,
    }


class AnnotationOperations:
    """PromptDatabase mixin: image tag sets, fingerprints and cheap reads.

    ``_`` helpers take the open ``_pair_transaction`` connection.
    """

    @contextmanager
    def _annotation_read(self) -> Iterator[sqlite3.Connection]:
        """One deferred read transaction, so paired SELECTs see one snapshot."""
        conn = self.model.get_connection()
        if conn.in_transaction:
            raise sqlite3.ProgrammingError(
                "Annotation reads require their own snapshot"
            )
        with conn:
            conn.execute("BEGIN")
            yield conn

    @staticmethod
    def _annotation_owner(conn: sqlite3.Connection, locator: str, now: str) -> str:
        row = conn.execute(_OWNER, (locator,)).fetchone()
        if row is not None:
            return row[0]
        file_id = _new_id()
        conn.execute(_INSERT_OWNER, (file_id, locator, now))
        return file_id

    @staticmethod
    def _annotation_byte(
        conn: sqlite3.Connection,
        file_id: str,
        sha256: str,
        size: int,
        mtime_ns: int,
        now: str,
    ) -> tuple[str, int, bool, bool]:
        """The byte record for these bytes, refreshed or created.

        Returns ``(id, tag_revision, created, refingerprinted)``; the last is
        True when an existing record's verified ``(size, mtime_ns)`` changed,
        which moves its currency for cheap reads (the caller bumps the index
        revision when nothing else does).
        """
        row = conn.execute(_BYTE, (file_id, sha256)).fetchone()
        if row is None:
            byte_id = _new_id()
            conn.execute(
                _INSERT_BYTE, (byte_id, file_id, sha256, size, mtime_ns, now, now)
            )
            return byte_id, 0, True, False
        conn.execute(_REFRESH_BYTE, (size, mtime_ns, now, row[0]))
        return row[0], row[1], False, (row[2], row[3]) != (size, mtime_ns)

    @staticmethod
    def _byte_tags(conn: sqlite3.Connection, byte_id: str) -> list[str]:
        return [row[0] for row in conn.execute(_BYTE_TAGS, (byte_id,))]

    def _write_image_tags(
        self, conn: sqlite3.Connection, byte_id: str, tags: list[str]
    ) -> int:
        """Rewrite the junction in order, bump both revisions; return the new one."""
        tag_ids = self._ensure_tags(conn, tags)
        conn.execute(_CLEAR_TAGS, (byte_id,))
        conn.executemany(
            _INSERT_TAG,
            [(byte_id, tag_ids[name], position) for position, name in enumerate(tags)],
        )
        conn.execute(_BUMP_REVISION, (byte_id,))
        conn.execute(_BUMP_INDEX)
        return conn.execute(_REVISION, (byte_id,)).fetchone()[0]

    def _current_set(self, conn, sha256, byte_id, revision) -> dict:
        return {
            "sha256": sha256,
            "tags": self._byte_tags(conn, byte_id),
            "tag_revision": revision,
        }

    def read_image_tags(self, locator: str, sha256: str) -> dict:
        """The stored set of these exact bytes, or an empty set at revision 0.

        ``prior_count`` is the number of other byte records at the locator
        (earlier or later bytes of the same file).
        """
        _validate_locator(locator)
        _validate_digest(sha256)
        with self._annotation_read() as conn:
            row = conn.execute(_READ, (sha256, sha256, locator)).fetchone()
            if row is None:
                return {"tags": [], "tag_revision": 0, "prior_count": 0}
            tags = self._byte_tags(conn, row[0]) if row[0] is not None else []
            return {"tags": tags, "tag_revision": row[1] or 0, "prior_count": row[2]}

    def replace_image_tags(
        self,
        *,
        locator: str,
        sha256: str,
        size: int,
        mtime_ns: int,
        expected_epoch: str,
        expected_tag_revision: int,
        tags: list,
    ) -> dict:
        """Replace the set of these exact bytes, guarded by epoch and revision.

        Creates the owner and byte record when the bytes are new (an explicit
        empty set is a real save). The identical set at the current revision,
        or one behind it (a lost-response retry), is ``replayed`` and writes
        nothing; any other revision mismatch is ``tag-conflict`` with the
        current set and no writes.
        """
        _validate_target(locator, sha256, size, mtime_ns)
        _validate_epoch(expected_epoch)
        _validate_int(expected_tag_revision, "expected_tag_revision", 0)
        tags = normalize_image_tags(tags)
        with self._pair_transaction() as conn:
            epoch = self._library_epoch(conn, expected_epoch)
            now = utc_now_iso()
            file_id = self._annotation_owner(conn, locator, now)
            byte_id, revision, created, refingerprinted = self._annotation_byte(
                conn, file_id, sha256, size, mtime_ns, now
            )
            current = self._byte_tags(conn, byte_id)
            if (
                not created
                and current == tags
                and expected_tag_revision in (revision, revision - 1)
            ):
                if refingerprinted:
                    conn.execute(_BUMP_INDEX)
                return _receipt(epoch, sha256, current, revision, True)
            if expected_tag_revision != revision:
                raise AnnotationCommandError(
                    "tag-conflict",
                    epoch,
                    {"sha256": sha256, "tags": current, "tag_revision": revision},
                )
            revision = self._write_image_tags(conn, byte_id, tags)
            return _receipt(epoch, sha256, tags, revision, False)

    def add_image_tags(
        self,
        *,
        locator: str,
        sha256: str,
        size: int,
        mtime_ns: int,
        expected_epoch: str,
        tags: list,
    ) -> dict:
        """Union ``tags`` into the set of these exact bytes, keeping stored spelling.

        ``added`` counts the names that were new (case-insensitively). A union
        over ``MAX_IMAGE_TAGS`` is ``tag-limit`` with the current set and no
        writes; a union that adds nothing to an existing record is ``replayed``.
        """
        _validate_target(locator, sha256, size, mtime_ns)
        _validate_epoch(expected_epoch)
        tags = normalize_image_tags(tags)
        with self._pair_transaction() as conn:
            epoch = self._library_epoch(conn, expected_epoch)
            now = utc_now_iso()
            file_id = self._annotation_owner(conn, locator, now)
            byte_id, revision, created, refingerprinted = self._annotation_byte(
                conn, file_id, sha256, size, mtime_ns, now
            )
            current = self._byte_tags(conn, byte_id)
            present = {name.casefold() for name in current}
            added = [name for name in tags if name.casefold() not in present]
            merged = current + added
            if len(merged) > MAX_IMAGE_TAGS:
                raise AnnotationCommandError(
                    "tag-limit",
                    epoch,
                    {"sha256": sha256, "tags": current, "tag_revision": revision},
                )
            if not created and not added:
                if refingerprinted:
                    conn.execute(_BUMP_INDEX)
                return {**_receipt(epoch, sha256, current, revision, True), "added": 0}
            revision = self._write_image_tags(conn, byte_id, merged)
            return {
                **_receipt(epoch, sha256, merged, revision, False),
                "added": len(added),
            }

    def refresh_image_fingerprint(
        self, locator: str, sha256: str, size: int, mtime_ns: int
    ) -> bool:
        """Record that these exact bytes were just seen with this stat.

        True when a byte record was refreshed; nothing is created and no tag
        or tag revision changes. The image index revision moves because the
        record's currency for cheap reads may have changed.
        """
        _validate_target(locator, sha256, size, mtime_ns)
        with self.model.get_connection() as conn:
            cursor = conn.execute(
                _REFRESH_BY_LOCATOR, (size, mtime_ns, utc_now_iso(), sha256, locator)
            )
            if cursor.rowcount > 0:
                conn.execute(_BUMP_INDEX)
            return cursor.rowcount > 0

    def current_image_tags(self, stats: dict) -> dict:
        """Image tags of the files whose current ``(size, mtime_ns)`` is verified.

        ``stats`` maps locators to their present fingerprint. A locator is
        answered (possibly with an empty set) only when a byte record carries
        exactly that verified fingerprint; the most recently verified record
        wins when several do. Lookups go in chunks of 500 locators.
        """
        if not isinstance(stats, dict):
            raise ValueError(
                "stats must map locators to (size, mtime_ns) integer pairs"
            )
        for locator, fingerprint in stats.items():
            _validate_fingerprint(locator, fingerprint)
        locators = list(stats)
        chosen: dict[str, tuple[tuple[str, str], str]] = {}
        result: dict[str, list[str]] = {}
        with self._annotation_read() as conn:
            for start in range(0, len(locators), _LOOKUP_CHUNK):
                chunk = locators[start : start + _LOOKUP_CHUNK]
                marks = ",".join("?" * len(chunk))
                for locator, byte_id, size, mtime_ns, verified_at in conn.execute(
                    _FINGERPRINTS.format(marks=marks), chunk
                ):
                    if (size, mtime_ns) != stats[locator]:
                        continue
                    key = (verified_at, byte_id)
                    if locator not in chosen or key > chosen[locator][0]:
                        chosen[locator] = (key, byte_id)
            owners = {byte_id: locator for locator, (_key, byte_id) in chosen.items()}
            result = {locator: [] for locator in chosen}
            byte_ids = list(owners)
            for start in range(0, len(byte_ids), _LOOKUP_CHUNK):
                chunk = byte_ids[start : start + _LOOKUP_CHUNK]
                marks = ",".join("?" * len(chunk))
                for byte_id, name in conn.execute(_TAGS_OF.format(marks=marks), chunk):
                    result[owners[byte_id]].append(name)
        return result

    def iter_image_tag_records(self) -> Iterator[tuple[str, int, int, list[str]]]:
        """Stream every byte record as ``(locator, size, mtime_ns, tags)``.

        One SELECT ordered by locator, then by the bytes' first sighting, with
        each set's names in position order.
        """
        conn = self.model.get_connection()
        current: tuple | None = None
        for locator, byte_id, size, mtime_ns, name in conn.execute(_RECORDS):
            if current is None or current[0] != byte_id:
                if current is not None:
                    yield current[1]
                current = (byte_id, (locator, size, mtime_ns, []))
            if name is not None:
                current[1][3].append(name)
        if current is not None:
            yield current[1]