import { mapWithConcurrency } from '@snowluma/common/concurrency';
import { createLogger } from '@snowluma/common/logger';
import type { BridgeInterface } from '@snowluma/core/bridge-interface';
import {
    LOGIN_HISTORY_SYNC_PROTOCOL_LIMITS,
    type GroupHistorySyncState,
    type PrivateHistorySyncState,
} from '@snowluma/core/apis';
import type { FriendMessage, GroupMessage } from '@snowluma/protocol/events';
import { convertEvent, type ConverterContext } from './event-converter';
import { persistHistoryEvent, toHistoryInt } from './history-persistence';
import type { MessageStore } from './message-store';

export const LOGIN_HISTORY_SYNC_LIMITS = {
    startupDelayMs: 30_000,
    scannedGroups: LOGIN_HISTORY_SYNC_PROTOCOL_LIMITS.maxTargetsPerKind,
    scannedPrivateUsers: LOGIN_HISTORY_SYNC_PROTOCOL_LIMITS.maxTargetsPerKind,
    maxGroups: 3,
    maxPrivateUsers: 3,
    messagesPerSession: LOGIN_HISTORY_SYNC_PROTOCOL_LIMITS.maxMessagesPerSession,
} as const;

export interface LoginHistorySyncClock {
    sleep(ms: number, signal: AbortSignal): Promise<void>;
}

export interface LoginHistorySyncRef {
    selfId: number;
    bridge: BridgeInterface;
    messageStore: MessageStore;
    converterCtx: ConverterContext;
}

export interface LoginHistorySyncResult {
    scannedGroups: number;
    scannedPrivateUsers: number;
    selectedGroups: number;
    selectedPrivateUsers: number;
    fetchedMessages: number;
    storedMessages: number;
    failedSessions: number;
    truncatedGroups: boolean;
    truncatedPrivateUsers: boolean;
}

interface GroupCandidate {
    state: GroupHistorySyncState;
    localSequence: number | null;
    priority: number;
    knownGap: boolean;
}

interface PrivateCandidate {
    state: PrivateHistorySyncState;
    localSequence: number | null;
    priority: number;
    knownGap: boolean;
}

const log = createLogger('OneBot.HistorySync');

const SYSTEM_CLOCK: LoginHistorySyncClock = {
    sleep: (ms, signal) => abortableSleep(ms, signal),
};

/**
 * Process-wide coordinator for automatic login backfill.
 *
 * The 30-second grace period happens before entering the global FIFO, so one
 * account waiting out startup does not block another account that is already
 * ready. The complete per-account operation is serialized so conversion and
 * persistence cannot overlap another account's automatic sync.
 */
export class LoginHistorySyncCoordinator {
    private tail: Promise<void> = Promise.resolve();

    constructor(private readonly clock: LoginHistorySyncClock = SYSTEM_CLOCK) {}

    async schedule(ref: LoginHistorySyncRef, signal: AbortSignal): Promise<LoginHistorySyncResult> {
        await this.clock.sleep(LOGIN_HISTORY_SYNC_LIMITS.startupDelayMs, signal);
        throwIfAborted(signal);

        let operationStarted = false;
        const operation = this.tail.then(async () => {
            throwIfAborted(signal);
            operationStarted = true;
            return this.runAccount(ref, signal);
        });
        this.tail = operation.then(
            () => undefined,
            () => undefined,
        );
        return rejectWhileQueuedOnAbort(operation, signal, () => operationStarted);
    }

    private async runAccount(
        ref: LoginHistorySyncRef,
        signal: AbortSignal,
    ): Promise<LoginHistorySyncResult> {
        const groups = ref.bridge.identity.groups.filter(
            (group) => Number.isSafeInteger(group.groupId) && group.groupId > 0,
        );
        const privateUsers = ref.bridge.identity.friends.filter(
            (friend) =>
                Number.isSafeInteger(friend.uin) &&
                friend.uin > 0 &&
                friend.uin !== ref.selfId &&
                typeof friend.uid === 'string' &&
                friend.uid.trim().length > 0,
        );
        const truncatedGroups = groups.length > LOGIN_HISTORY_SYNC_LIMITS.scannedGroups;
        const truncatedPrivateUsers =
            privateUsers.length > LOGIN_HISTORY_SYNC_LIMITS.scannedPrivateUsers;
        const scannedGroups = groups.slice(0, LOGIN_HISTORY_SYNC_LIMITS.scannedGroups);
        const scannedPrivateUsers = privateUsers.slice(
            0,
            LOGIN_HISTORY_SYNC_LIMITS.scannedPrivateUsers,
        );

        if (truncatedGroups || truncatedPrivateUsers) {
            log.warn(
                'login history sync roster truncated: UIN=%d groups=%d/%d private=%d/%d',
                ref.selfId,
                scannedGroups.length,
                groups.length,
                scannedPrivateUsers.length,
                privateUsers.length,
            );
        }

        throwIfAborted(signal);
        const state = await ref.bridge.apis.message.probeHistorySyncState(
            scannedGroups.map((group) => group.groupId),
            scannedPrivateUsers.map((friend) => ({
                userId: friend.uin,
                uid: friend.uid,
            })),
            signal,
        );
        const groupCandidates = await selectGroupCandidates(ref.messageStore, state.groups);
        const privateCandidates = await selectPrivateCandidates(
            ref.messageStore,
            state.privateUsers,
        );
        // URL resolvers may issue additional QQ requests for rkeys or media
        // download addresses. Automatic backfill must stay inside its one-probe
        // plus six-page packet budget, so persist only URLs already present in the
        // history response. Message-id resolution and local media indexing remain
        // enabled.
        const mediaSegmentSink = ref.converterCtx.mediaSegmentSink;
        const persistenceRef: LoginHistorySyncRef = {
            ...ref,
            converterCtx: {
                ...ref.converterCtx,
                imageUrlResolver: null,
                mediaUrlResolver: null,
                mediaSegmentSink: mediaSegmentSink
                    ? async (mediaType, element, data, isGroup, sessionId) => {
                          throwIfAborted(signal);
                          await mediaSegmentSink(mediaType, element, data, isGroup, sessionId);
                      }
                    : null,
            },
        };

        const result: LoginHistorySyncResult = {
            scannedGroups: scannedGroups.length,
            scannedPrivateUsers: scannedPrivateUsers.length,
            selectedGroups: groupCandidates.length,
            selectedPrivateUsers: privateCandidates.length,
            fetchedMessages: 0,
            storedMessages: 0,
            failedSessions: 0,
            truncatedGroups,
            truncatedPrivateUsers,
        };
        log.info(
            'login history sync selected: UIN=%d scanned=%d/%d selected=%d/%d',
            ref.selfId,
            result.scannedGroups,
            result.scannedPrivateUsers,
            result.selectedGroups,
            result.selectedPrivateUsers,
        );

        for (const candidate of groupCandidates) {
            throwIfAborted(signal);

            try {
                const messages = await fetchGroupCandidate(persistenceRef, candidate, signal);
                throwIfAborted(signal);
                result.fetchedMessages += messages.length;

                for (const message of messages) {
                    throwIfAborted(signal);
                    await persistGroupMessage(persistenceRef, message, signal);
                    result.storedMessages += 1;
                }
            } catch (error) {
                if (signal.aborted) {
                    throwIfAborted(signal);
                }

                result.failedSessions += 1;
                log.warn(
                    'login history sync group failed: UIN=%d group=%d error=%s',
                    ref.selfId,
                    candidate.state.groupId,
                    errorText(error),
                );
            }
        }

        for (const candidate of privateCandidates) {
            throwIfAborted(signal);

            try {
                const messages = await fetchPrivateCandidate(persistenceRef, candidate, signal);
                throwIfAborted(signal);
                result.fetchedMessages += messages.length;

                for (const message of messages) {
                    throwIfAborted(signal);

                    if (
                        await persistPrivateMessage(
                            persistenceRef,
                            candidate.state.userId,
                            message,
                            signal,
                        )
                    ) {
                        result.storedMessages += 1;
                    }
                }
            } catch (error) {
                if (signal.aborted) {
                    throwIfAborted(signal);
                }

                result.failedSessions += 1;
                log.warn(
                    'login history sync private failed: UIN=%d peer=%d error=%s',
                    ref.selfId,
                    candidate.state.userId,
                    errorText(error),
                );
            }
        }

        log.info(
            'login history sync complete: UIN=%d fetched=%d stored=%d failed=%d',
            ref.selfId,
            result.fetchedMessages,
            result.storedMessages,
            result.failedSessions,
        );
        return result;
    }
}

export const loginHistorySyncCoordinator = new LoginHistorySyncCoordinator();

async function selectGroupCandidates(
    store: MessageStore,
    states: readonly GroupHistorySyncState[],
): Promise<GroupCandidate[]> {
    return (
        await mapWithConcurrency(states, 8, async (state): Promise<GroupCandidate[]> => {
            if (!Number.isSafeInteger(state.latestSeq) || state.latestSeq <= 0) {
                return [];
            }

            const observedSequence = await store.findLatestAuthoritativeSequence(
                true,
                state.groupId,
            );
            const localSequence = await store.findLatestPersistedAuthoritativeSequence(
                true,
                state.groupId,
            );

            if (localSequence !== null) {
                if (state.latestSeq <= localSequence) {
                    return [];
                }

                return [
                    {
                        state,
                        localSequence,
                        priority: state.latestSeq - localSequence,
                        knownGap: true,
                    },
                ];
            }

            if (observedSequence !== null) {
                return [
                    {
                        state,
                        localSequence: null,
                        priority: state.latestSeq,
                        knownGap: true,
                    },
                ];
            }

            if (state.latestSeq <= state.readSeq) {
                return [];
            }

            return [
                {
                    state,
                    localSequence: null,
                    priority: state.latestSeq - state.readSeq,
                    knownGap: false,
                },
            ];
        })
    )
        .flat()
        .sort(compareCandidates)
        .slice(0, LOGIN_HISTORY_SYNC_LIMITS.maxGroups);
}

async function selectPrivateCandidates(
    store: MessageStore,
    states: readonly PrivateHistorySyncState[],
): Promise<PrivateCandidate[]> {
    return (
        await mapWithConcurrency(states, 8, async (state): Promise<PrivateCandidate[]> => {
            if (!Number.isSafeInteger(state.latestSeq) || state.latestSeq <= 0) {
                return [];
            }

            const observedSequence = await store.findLatestAuthoritativeSequence(
                false,
                state.userId,
            );
            const localSequence = await store.findLatestPersistedAuthoritativeSequence(
                false,
                state.userId,
            );

            if (localSequence !== null) {
                if (state.latestSeq <= localSequence) {
                    return [];
                }

                return [
                    {
                        state,
                        localSequence,
                        priority: state.latestSeq - localSequence,
                        knownGap: true,
                    },
                ];
            }

            if (!Number.isSafeInteger(state.lastMsgTime) || state.lastMsgTime <= 0) {
                return [];
            }

            return [
                {
                    state,
                    localSequence: null,
                    priority: state.lastMsgTime,
                    knownGap: observedSequence !== null,
                },
            ];
        })
    )
        .flat()
        .sort(compareCandidates)
        .slice(0, LOGIN_HISTORY_SYNC_LIMITS.maxPrivateUsers);
}

function compareCandidates<
    T extends {
        localSequence: number | null;
        priority: number;
        knownGap: boolean;
    },
>(left: T, right: T): number {
    if (left.knownGap !== right.knownGap) {
        return left.knownGap ? -1 : 1;
    }

    if ((left.localSequence !== null) !== (right.localSequence !== null)) {
        return left.localSequence !== null ? -1 : 1;
    }

    return right.priority - left.priority;
}

function fetchGroupCandidate(
    ref: LoginHistorySyncRef,
    candidate: GroupCandidate,
    signal: AbortSignal,
): Promise<GroupMessage[]> {
    const endSeq =
        candidate.localSequence === null
            ? candidate.state.latestSeq
            : Math.min(
                  candidate.state.latestSeq,
                  candidate.localSequence + LOGIN_HISTORY_SYNC_LIMITS.messagesPerSession,
              );
    const startSeq =
        candidate.localSequence === null
            ? Math.max(1, endSeq - LOGIN_HISTORY_SYNC_LIMITS.messagesPerSession + 1)
            : candidate.localSequence + 1;
    return ref.bridge.apis.message.getGroupHistorySyncPage(
        candidate.state.groupId,
        startSeq,
        endSeq,
        ref.selfId,
        signal,
    );
}

function fetchPrivateCandidate(
    ref: LoginHistorySyncRef,
    candidate: PrivateCandidate,
    signal: AbortSignal,
): Promise<FriendMessage[]> {
    if (candidate.localSequence !== null) {
        const endSeq = Math.min(
            candidate.state.latestSeq,
            candidate.localSequence + LOGIN_HISTORY_SYNC_LIMITS.messagesPerSession,
        );
        return ref.bridge.apis.message.getC2cHistorySyncPage(
            candidate.state.uid,
            candidate.localSequence + 1,
            endSeq,
            ref.selfId,
            signal,
        );
    }

    const beforeTime = Math.min(0xffff_ffff, candidate.state.lastMsgTime + 1);
    return ref.bridge.apis.message.getC2cLatestHistorySyncPage(
        candidate.state.uid,
        LOGIN_HISTORY_SYNC_LIMITS.messagesPerSession,
        ref.selfId,
        beforeTime,
        signal,
    );
}

async function persistGroupMessage(
    ref: LoginHistorySyncRef,
    message: GroupMessage,
    signal: AbortSignal,
): Promise<void> {
    throwIfAborted(signal);
    const converted = await convertEvent(ref.converterCtx, message);
    throwIfAborted(signal);

    if (!converted || converted.message_type !== 'group') {
        throw new Error(
            `group history conversion failed: group=${message.groupId} seq=${message.msgSeq} ` +
                `messageType=${String(converted?.message_type)}`,
        );
    }

    await persistHistoryEvent(ref.messageStore, converted);
}

async function persistPrivateMessage(
    ref: LoginHistorySyncRef,
    peerUin: number,
    message: FriendMessage,
    signal: AbortSignal,
): Promise<boolean> {
    throwIfAborted(signal);
    const receivedPeer = message.peerUin ?? 0;

    if (receivedPeer > 0 && receivedPeer !== peerUin) {
        throw new Error(
            `private history peer mismatch: requested=${peerUin} received=${receivedPeer} ` +
                `seq=${String(message.ntMsgSeq ?? message.msgSeq)}`,
        );
    }

    if (receivedPeer <= 0) {
        message.peerUin = peerUin;
    }

    const clientSequence = message.clientSeq ?? message.msgSeq;
    const sentBySelf = message.senderUin === ref.selfId;
    const converted = await convertEvent(ref.converterCtx, message);
    throwIfAborted(signal);

    if (!converted || converted.message_type !== 'private') {
        throw new Error(
            `private history conversion failed: peer=${peerUin} ` +
                `seq=${String(message.ntMsgSeq ?? message.msgSeq)} ` +
                `messageType=${String(converted?.message_type)}`,
        );
    }

    if (
        await ref.messageStore.isPrivateMessageRecalled(
            peerUin,
            clientSequence,
            sentBySelf,
            message.time,
        )
    ) {
        log.debug(
            'login history sync omitted recalled private message: UIN=%d peer=%d clientSeq=%d self=%s',
            ref.selfId,
            peerUin,
            clientSequence,
            String(sentBySelf),
        );
        return false;
    }

    if (converted.post_type === 'message_sent' && toHistoryInt(converted.target_id) === 0) {
        converted.target_id = peerUin;
    }

    return persistHistoryEvent(ref.messageStore, converted, peerUin, message);
}

function abortableSleep(ms: number, signal: AbortSignal): Promise<void> {
    throwIfAborted(signal);
    return new Promise<void>((resolve, reject) => {
        const timer = setTimeout(() => {
            signal.removeEventListener('abort', onAbort);
            resolve();
        }, ms);
        timer.unref();

        const onAbort = () => {
            clearTimeout(timer);
            reject(signal.reason ?? new Error('login history sync aborted'));
        };

        signal.addEventListener('abort', onAbort, { once: true });
    });
}

function throwIfAborted(signal: AbortSignal): void {
    if (signal.aborted) {
        throw signal.reason ?? new Error('login history sync aborted');
    }
}

function rejectWhileQueuedOnAbort<T>(
    result: Promise<T>,
    signal: AbortSignal,
    hasStarted: () => boolean,
): Promise<T> {
    if (signal.aborted && !hasStarted()) {
        return Promise.reject(signal.reason ?? new Error('login history sync aborted'));
    }

    return new Promise<T>((resolve, reject) => {
        const onAbort = () => {
            if (!hasStarted()) {
                signal.removeEventListener('abort', onAbort);
                reject(signal.reason ?? new Error('login history sync aborted'));
            }
        };

        signal.addEventListener('abort', onAbort);
        result.then(resolve, reject).finally(() => {
            signal.removeEventListener('abort', onAbort);
        });
    });
}

function errorText(error: unknown): string {
    return error instanceof Error ? (error.stack ?? error.message) : String(error);
}