from typing import Dict, Iterable, List, Optional, Tuple, Union

from django.contrib.auth.models import AnonymousUser
from django.http import HttpRequest, HttpResponse
from django.utils.html import escape as escape_html
from django.utils.translation import gettext as _
from sqlalchemy.sql import and_, column, join, literal, literal_column, select, table
from sqlalchemy.types import Integer, Text

from zerver.context_processors import get_valid_realm_from_request
from zerver.lib.exceptions import JsonableError, MissingAuthenticationError
from zerver.lib.message import get_first_visible_message_id, messages_for_ids
from zerver.lib.narrow import (
    NarrowBuilder,
    OptionalNarrowListT,
    fetch_messages,
    is_spectator_compatible,
    is_web_public_narrow,
    narrow_parameter,
    parse_anchor_value,
)
from zerver.lib.request import REQ, RequestNotes, has_request_variables
from zerver.lib.response import json_success
from zerver.lib.sqlalchemy_utils import get_sqlalchemy_connection
from zerver.lib.topic import DB_TOPIC_NAME, MATCH_TOPIC, topic_column_sa
from zerver.lib.utils import statsd
from zerver.lib.validator import check_bool, check_int, check_list, to_non_negative_int
from zerver.models import UserMessage, UserProfile

MAX_MESSAGES_PER_FETCH = 5000


def highlight_string(text: str, locs: Iterable[Tuple[int, int]]) -> str:
    highlight_start = '<span class="highlight">'
    highlight_stop = "</span>"
    pos = 0
    result = ""
    in_tag = False

    for loc in locs:
        (offset, length) = loc

        prefix_start = pos
        prefix_end = offset
        match_start = offset
        match_end = offset + length

        prefix = text[prefix_start:prefix_end]
        match = text[match_start:match_end]

        for character in prefix + match:
            if character == "<":
                in_tag = True
            elif character == ">":
                in_tag = False
        if in_tag:
            result += prefix
            result += match
        else:
            result += prefix
            result += highlight_start
            result += match
            result += highlight_stop
        pos = match_end

    result += text[pos:]
    return result


def get_search_fields(
    rendered_content: str,
    topic_name: str,
    content_matches: Iterable[Tuple[int, int]],
    topic_matches: Iterable[Tuple[int, int]],
) -> Dict[str, str]:
    return {
        "match_content": highlight_string(rendered_content, content_matches),
        MATCH_TOPIC: highlight_string(escape_html(topic_name), topic_matches),
    }


@has_request_variables
def get_messages_backend(
    request: HttpRequest,
    maybe_user_profile: Union[UserProfile, AnonymousUser],
    anchor_val: Optional[str] = REQ("anchor", default=None),
    include_anchor: bool = REQ(json_validator=check_bool, default=True),
    num_before: int = REQ(converter=to_non_negative_int),
    num_after: int = REQ(converter=to_non_negative_int),
    narrow: OptionalNarrowListT = REQ("narrow", converter=narrow_parameter, default=None),
    use_first_unread_anchor_val: bool = REQ(
        "use_first_unread_anchor", json_validator=check_bool, default=False
    ),
    client_gravatar: bool = REQ(json_validator=check_bool, default=True),
    apply_markdown: bool = REQ(json_validator=check_bool, default=True),
) -> HttpResponse:
    anchor = parse_anchor_value(anchor_val, use_first_unread_anchor_val)
    if num_before + num_after > MAX_MESSAGES_PER_FETCH:
        raise JsonableError(
            _("Too many messages requested (maximum {}).").format(
                MAX_MESSAGES_PER_FETCH,
            )
        )
    if num_before > 0 and num_after > 0 and not include_anchor:
        raise JsonableError(_("The anchor can only be excluded at an end of the range"))

    realm = get_valid_realm_from_request(request)
    if not maybe_user_profile.is_authenticated:
        # If user is not authenticated, clients must include
        # `streams:web-public` in their narrow query to indicate this
        # is a web-public query.  This helps differentiate between
        # cases of web-public queries (where we should return the
        # web-public results only) and clients with buggy
        # authentication code (where we should return an auth error).
        #
        # GetOldMessagesTest.test_unauthenticated_* tests ensure
        # that we are not leaking any secure data (private messages and
        # non-web-public stream messages) via this path.
        if not realm.allow_web_public_streams_access():
            raise MissingAuthenticationError
        if not is_web_public_narrow(narrow):
            raise MissingAuthenticationError
        assert narrow is not None
        if not is_spectator_compatible(narrow):
            raise MissingAuthenticationError

        # We use None to indicate unauthenticated requests as it's more
        # readable than using AnonymousUser, and the lack of Django
        # stubs means that mypy can't check AnonymousUser well.
        user_profile: Optional[UserProfile] = None
        is_web_public_query = True
    else:
        assert isinstance(maybe_user_profile, UserProfile)
        user_profile = maybe_user_profile
        assert user_profile is not None
        is_web_public_query = False

    assert realm is not None

    if is_web_public_query:
        # client_gravatar here is just the user-requested value. "finalize_payload" function
        # is responsible for sending avatar_url based on each individual sender's
        # email_address_visibility setting.
        client_gravatar = False

    if narrow is not None:
        # Add some metadata to our logging data for narrows
        verbose_operators = []
        for term in narrow:
            if term["operator"] == "is":
                verbose_operators.append("is:" + term["operand"])
            else:
                verbose_operators.append(term["operator"])
        log_data = RequestNotes.get_notes(request).log_data
        assert log_data is not None
        log_data["extra"] = "[{}]".format(",".join(verbose_operators))

    query_info = fetch_messages(
        narrow=narrow,
        user_profile=user_profile,
        realm=realm,
        is_web_public_query=is_web_public_query,
        anchor=anchor,
        include_anchor=include_anchor,
        num_before=num_before,
        num_after=num_after,
    )

    anchor = query_info.anchor
    include_history = query_info.include_history
    is_search = query_info.is_search
    rows = query_info.rows

    # The following is a little messy, but ensures that the code paths
    # are similar regardless of the value of include_history.  The
    # 'user_messages' dictionary maps each message to the user's
    # UserMessage object for that message, which we will attach to the
    # rendered message dict before returning it.  We attempt to
    # bulk-fetch rendered message dicts from remote cache using the
    # 'messages' list.
    message_ids: List[int] = []
    user_message_flags: Dict[int, List[str]] = {}
    if is_web_public_query:
        # For spectators, we treat all historical messages as read.
        for row in rows:
            message_id = row[0]
            message_ids.append(message_id)
            user_message_flags[message_id] = ["read"]
    elif include_history:
        assert user_profile is not None
        message_ids = [row[0] for row in rows]

        # TODO: This could be done with an outer join instead of two queries
        um_rows = UserMessage.objects.filter(user_profile=user_profile, message_id__in=message_ids)
        user_message_flags = {um.message_id: um.flags_list() for um in um_rows}

        for message_id in message_ids:
            if message_id not in user_message_flags:
                user_message_flags[message_id] = ["read", "historical"]
    else:
        for row in rows:
            message_id = row[0]
            flags = row[1]
            user_message_flags[message_id] = UserMessage.flags_list_for_flags(flags)
            message_ids.append(message_id)

    search_fields: Dict[int, Dict[str, str]] = {}
    if is_search:
        for row in rows:
            message_id = row[0]
            (topic_name, rendered_content, content_matches, topic_matches) = row[-4:]
            search_fields[message_id] = get_search_fields(
                rendered_content, topic_name, content_matches, topic_matches
            )

    message_list = messages_for_ids(
        message_ids=message_ids,
        user_message_flags=user_message_flags,
        search_fields=search_fields,
        apply_markdown=apply_markdown,
        client_gravatar=client_gravatar,
        allow_edit_history=realm.allow_edit_history,
    )

    statsd.incr("loaded_old_messages", len(message_list))

    ret = dict(
        messages=message_list,
        result="success",
        msg="",
        found_anchor=query_info.found_anchor,
        found_oldest=query_info.found_oldest,
        found_newest=query_info.found_newest,
        history_limited=query_info.history_limited,
        anchor=anchor,
    )
    return json_success(request, data=ret)


@has_request_variables
def messages_in_narrow_backend(
    request: HttpRequest,
    user_profile: UserProfile,
    msg_ids: List[int] = REQ(json_validator=check_list(check_int)),
    narrow: OptionalNarrowListT = REQ(converter=narrow_parameter),
) -> HttpResponse:
    first_visible_message_id = get_first_visible_message_id(user_profile.realm)
    msg_ids = [message_id for message_id in msg_ids if message_id >= first_visible_message_id]
    # This query is limited to messages the user has access to because they
    # actually received them, as reflected in `zerver_usermessage`.
    query = (
        select(column("message_id", Integer), topic_column_sa(), column("rendered_content", Text))
        .where(
            and_(
                column("user_profile_id", Integer) == literal(user_profile.id),
                column("message_id", Integer).in_(msg_ids),
            )
        )
        .select_from(
            join(
                table("zerver_usermessage"),
                table("zerver_message"),
                literal_column("zerver_usermessage.message_id", Integer)
                == literal_column("zerver_message.id", Integer),
            )
        )
    )

    builder = NarrowBuilder(user_profile, column("message_id", Integer), user_profile.realm)
    if narrow is not None:
        for term in narrow:
            query = builder.add_term(query, term)

    search_fields = {}
    with get_sqlalchemy_connection() as sa_conn:
        for row in sa_conn.execute(query).fetchall():
            message_id = row._mapping["message_id"]
            topic_name = row._mapping[DB_TOPIC_NAME]
            rendered_content = row._mapping["rendered_content"]
            if "content_matches" in row._mapping:
                content_matches = row._mapping["content_matches"]
                topic_matches = row._mapping["topic_matches"]
            else:
                content_matches = topic_matches = []
            search_fields[str(message_id)] = get_search_fields(
                rendered_content,
                topic_name,
                content_matches,
                topic_matches,
            )

    return json_success(request, data={"messages": search_fields})