import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
import { PlatformGraphqlService } from '../platform/platform-graphql.service';

// AgentEvent enum values (mirror of the SDK app's agent-event.object.ts).
// Ozonetel webhook actions → Helix event types.
export type AgentEventType =
    | 'LOGIN'
    | 'LOGOUT'
    | 'READY'
    | 'PAUSE'
    | 'RESUME'
    | 'CALL_START'
    | 'CALL_END'
    | 'ACW_START'
    | 'ACW_END';

// Separate pending slots per event category. Call + ACW overlap (agent
// enters ACW before the CALL_END arrives), so a single shared slot would
// let ACW_START clobber pending CALL_START and produce 0-second call
// durations. Keep one slot per category so each END event pairs cleanly.
type PendingSlot = 'pause' | 'call' | 'acw';
type PendingStarts = {
    pause?: number; // PAUSE eventAt ms
    call?: number;  // CALL_START eventAt ms
    acw?: number;   // ACW_START eventAt ms
};

/**
 * Persists agent activity and per-call timing into the platform entities
 * we added in Phase 1 (AgentEvent, Call SLA fields). Reads AgentSession
 * later via the rollup job.
 *
 * Called from:
 *  - supervisor.service.handleAgentEvent → persistAgentEvent()
 *  - supervisor.service.handleCallEvent → patchCallTiming()
 *  - ozonetel-agent.controller dispose flow → patchCallTiming()
 */
@Injectable()
export class AgentHistoryService implements OnModuleInit {
    private readonly logger = new Logger(AgentHistoryService.name);

    // ozonetelAgentId → Agent entity UUID. Loaded at startup.
    private readonly agentUuidByOzonetelId = new Map<string, string>();

    // agentId → map of pending start events per category, used to compute
    // durationSec on the matching END event.
    private readonly pendingStartsByAgent = new Map<string, PendingStarts>();

    constructor(private readonly platform: PlatformGraphqlService) {}

    private rollupTimer: NodeJS.Timeout | null = null;

    async onModuleInit() {
        await this.refreshAgentCache();
        // Roll up today's sessions every 15 minutes. Rollup is idempotent
        // (upsert by agent+date), so missing a tick is safe — the next tick
        // recomputes from AgentEvent history. Written with setInterval because
        // @nestjs/schedule isn't installed in this sidecar.
        this.rollupTimer = setInterval(() => {
            this.rollupSessions(this.currentSessionDate()).catch((err) => {
                this.logger.warn(`[HISTORY] Rollup tick failed: ${err?.message ?? err}`);
            });
        }, 15 * 60 * 1000);
        // Kick off one immediately so the dashboard has data on boot.
        this.rollupSessions(this.currentSessionDate()).catch(() => {});
    }

    onModuleDestroy() {
        if (this.rollupTimer) clearInterval(this.rollupTimer);
    }

    // IST day boundary — agents work in IST, so the rollup is by IST date.
    private currentSessionDate(): string {
        const now = new Date();
        const ist = new Date(now.getTime() + 5.5 * 60 * 60 * 1000);
        return ist.toISOString().slice(0, 10);
    }

    private async refreshAgentCache(): Promise<void> {
        try {
            const data = await this.platform.query<any>(
                `{ agents(first: 50) { edges { node { id ozonetelAgentId } } } }`,
            );
            const edges = data?.agents?.edges ?? [];
            this.agentUuidByOzonetelId.clear();
            for (const edge of edges) {
                const n = edge.node;
                if (n.ozonetelAgentId) {
                    this.agentUuidByOzonetelId.set(n.ozonetelAgentId, n.id);
                }
            }
            this.logger.log(`[HISTORY] Loaded ${this.agentUuidByOzonetelId.size} agent UUIDs into cache`);
        } catch (err) {
            this.logger.warn(`[HISTORY] Failed to refresh agent cache: ${err}`);
        }
    }

    private async resolveAgentUuid(ozonetelAgentId: string): Promise<string | null> {
        if (!ozonetelAgentId) return null;
        const cached = this.agentUuidByOzonetelId.get(ozonetelAgentId);
        if (cached) return cached;
        // Cache miss — refresh once (handles late-provisioned agents like Ganesh)
        await this.refreshAgentCache();
        return this.agentUuidByOzonetelId.get(ozonetelAgentId) ?? null;
    }

    /**
     * Record an agent activity event. Computes durationSec for END events
     * (RESUME, CALL_END, ACW_END) by pairing against the most recent START.
     * Non-fatal on failure — realtime SSE flow continues even if the
     * platform write errors.
     */
    async persistAgentEvent(params: {
        ozonetelAgentId: string;
        eventType: AgentEventType;
        eventAt: string; // ISO
        pauseReason?: string | null;
        callId?: string | null;
    }): Promise<void> {
        const agentUuid = await this.resolveAgentUuid(params.ozonetelAgentId);
        if (!agentUuid) {
            this.logger.warn(`[HISTORY] No Agent entity for ozonetelAgentId=${params.ozonetelAgentId} — skipping event persist`);
            return;
        }

        // Pair START → END events by category. CALL and ACW can overlap
        // (agent enters ACW before CALL_END arrives), so each lives in its
        // own slot. READY is a fallback close — supervisor.service already
        // maps 'release'/'IDLE' to RESUME / ACW_END when it knows the prior
        // state; READY only fires when that disambiguation failed, so it
        // clears anything dangling.
        let durationSec: number | null = null;
        const endSlot = this.slotForEnd(params.eventType);
        const startSlot = this.slotForStart(params.eventType);
        const eventMs = new Date(params.eventAt).getTime();

        if (endSlot) {
            const pending = this.pendingStartsByAgent.get(params.ozonetelAgentId);
            const at = pending?.[endSlot];
            if (at !== undefined) {
                durationSec = Math.max(0, Math.round((eventMs - at) / 1000));
                delete pending![endSlot];
                if (!pending!.pause && !pending!.call && !pending!.acw) {
                    this.pendingStartsByAgent.delete(params.ozonetelAgentId);
                }
            }
        } else if (startSlot) {
            const existing = this.pendingStartsByAgent.get(params.ozonetelAgentId) ?? {};
            existing[startSlot] = eventMs;
            this.pendingStartsByAgent.set(params.ozonetelAgentId, existing);
        } else if (params.eventType === 'READY' || params.eventType === 'LOGOUT') {
            // Defensive flush of any lingering slots on session boundaries.
            this.pendingStartsByAgent.delete(params.ozonetelAgentId);
        }

        const data: Record<string, any> = {
            name: `${params.ozonetelAgentId} ${params.eventType}`,
            eventType: params.eventType,
            eventAt: params.eventAt,
            source: 'OZONETEL_SUBSCRIPTION',
            agentId: agentUuid,
        };
        if (params.pauseReason) data.pauseReason = params.pauseReason;
        if (durationSec !== null) data.durationS = durationSec;
        if (params.callId) data.callId = params.callId;

        try {
            await this.platform.query<any>(
                `mutation($data: AgentEventCreateInput!) { createAgentEvent(data: $data) { id } }`,
                { data },
            );
        } catch (err: any) {
            if (this.isEntityMissingError(err)) {
                if (!this.warnedEntityMissing) {
                    this.logger.warn('[HISTORY] AgentEvent entity not synced on this workspace — skipping persistence');
                    this.warnedEntityMissing = true;
                }
                return;
            }
            this.logger.warn(`[HISTORY] createAgentEvent failed: ${err}`);
        }
    }

    private warnedEntityMissing = false;

    private isEntityMissingError(err: unknown): boolean {
        const msg = String((err as any)?.message ?? err ?? '');
        return msg.includes('Cannot query field') || msg.includes('Unknown type')
            || msg.includes('AgentEventCreateInput') || msg.includes('AgentSessionCreateInput');
    }

    private slotForStart(eventType: AgentEventType): PendingSlot | null {
        if (eventType === 'PAUSE') return 'pause';
        if (eventType === 'CALL_START') return 'call';
        if (eventType === 'ACW_START') return 'acw';
        return null;
    }

    private slotForEnd(eventType: AgentEventType): PendingSlot | null {
        if (eventType === 'RESUME') return 'pause';
        if (eventType === 'CALL_END') return 'call';
        if (eventType === 'ACW_END') return 'acw';
        return null;
    }

    /**
     * Patch a Call record with SLA / timing fields derived from Ozonetel
     * webhooks or post-call CDR. All fields optional — caller passes only
     * what it has. Used for response-time and ACW histograms on the
     * supervisor dashboard.
     */
    async patchCallTiming(callId: string, fields: {
        assignedAt?: string;
        answeredAt?: string;
        responseTimeSec?: number;
        handlingTimeSec?: number;
        acwDurationSec?: number;
        holdDurationSec?: number;
    }): Promise<void> {
        // Platform truncates `*Sec` → `*S` on field names.
        const fieldNameMap: Record<string, string> = {
            responseTimeSec: 'responseTimeS',
            handlingTimeSec: 'handlingTimeS',
            acwDurationSec: 'acwDurationS',
            holdDurationSec: 'holdDurationS',
        };
        const data: Record<string, any> = {};
        for (const [k, v] of Object.entries(fields)) {
            if (v !== undefined && v !== null) {
                data[fieldNameMap[k] ?? k] = v;
            }
        }
        if (Object.keys(data).length === 0) return;
        try {
            await this.platform.query<any>(
                `mutation($id: UUID!, $data: CallUpdateInput!) { updateCall(id: $id, data: $data) { id } }`,
                { id: callId, data },
            );
        } catch (err) {
            this.logger.warn(`[HISTORY] updateCall timing failed (${callId}): ${err}`);
        }
    }

    /**
     * Aggregate AgentEvent rows into an AgentSession row per agent for the
     * given IST date. Called on a 15-minute interval; upserts by (agent,
     * sessionDate) so re-runs are safe.
     */
    async rollupSessions(sessionDate: string): Promise<void> {
        if (this.agentUuidByOzonetelId.size === 0) await this.refreshAgentCache();
        const agentUuids = Array.from(new Set(this.agentUuidByOzonetelId.values()));
        if (agentUuids.length === 0) return;

        const startIso = `${sessionDate}T00:00:00+05:30`;
        const endIso = `${sessionDate}T23:59:59+05:30`;

        let succeeded = 0;
        for (const agentUuid of agentUuids) {
            try {
                const events = await this.fetchAgentEvents(agentUuid, startIso, endIso);
                const totals = this.aggregateEvents(events);
                await this.upsertSession(agentUuid, sessionDate, totals);
                succeeded++;
            } catch (err: any) {
                if (this.isEntityMissingError(err)) {
                    if (!this.warnedEntityMissing) {
                        this.logger.warn('[HISTORY] AgentEvent/AgentSession entities not synced on this workspace — skipping rollup');
                        this.warnedEntityMissing = true;
                    }
                    return;
                }
                this.logger.warn(`[HISTORY] Rollup failed for agent ${agentUuid}: ${err?.message ?? err}`);
            }
        }
        this.logger.log(`[HISTORY] Rollup complete for ${sessionDate} — ${succeeded}/${agentUuids.length} agents`);
    }

    // Platform strips the `Sec` suffix on numeric field names — schema uses
    // `durationS`, `loginDurationS`, etc. Map back to our canonical names
    // when reading.
    private async fetchAgentEvents(agentUuid: string, startIso: string, endIso: string): Promise<Array<{ eventType: AgentEventType; durationSec: number | null; eventAt: string }>> {
        const events: Array<{ eventType: AgentEventType; durationSec: number | null; eventAt: string }> = [];
        let after: string | null = null;
        for (let page = 0; page < 20; page++) {
            const cursorArg: string = after ? `, after: "${after}"` : '';
            const data: any = await this.platform.query<any>(
                `{ agentEvents(first: 200${cursorArg}, filter: { agentId: { eq: "${agentUuid}" }, eventAt: { gte: "${startIso}", lte: "${endIso}" } }, orderBy: [{ eventAt: AscNullsLast }]) {
                    edges { node { eventType eventAt durationS } }
                    pageInfo { hasNextPage endCursor }
                } }`,
            );
            const edges = data?.agentEvents?.edges ?? [];
            for (const e of edges) {
                events.push({
                    eventType: e.node.eventType,
                    eventAt: e.node.eventAt,
                    durationSec: e.node.durationS ?? null,
                });
            }
            const pageInfo: { hasNextPage?: boolean; endCursor?: string } = data?.agentEvents?.pageInfo ?? {};
            if (!pageInfo.hasNextPage) break;
            after = pageInfo.endCursor ?? null;
        }
        return events;
    }

    private aggregateEvents(events: Array<{ eventType: AgentEventType; durationSec: number | null; eventAt: string }>) {
        let busyTimeSec = 0;
        let pauseTimeSec = 0;
        let wrapupTimeSec = 0;
        let handlingSum = 0;
        let handlingCount = 0;

        // Login duration: sum each LOGIN → (next LOGOUT on same day | now) span.
        // Ozonetel doesn't emit a LOGOUT if the agent just closes the tab, so
        // cap open sessions at the end of the rollup day.
        let loginDurationSec = 0;
        let openLoginAt: number | null = null;

        for (const e of events) {
            if (e.eventType === 'LOGIN') {
                openLoginAt = new Date(e.eventAt).getTime();
            } else if (e.eventType === 'LOGOUT' && openLoginAt !== null) {
                loginDurationSec += Math.max(0, Math.round((new Date(e.eventAt).getTime() - openLoginAt) / 1000));
                openLoginAt = null;
            } else if (e.eventType === 'CALL_END' && e.durationSec) {
                busyTimeSec += e.durationSec;
                handlingSum += e.durationSec;
                handlingCount++;
            } else if (e.eventType === 'RESUME' && e.durationSec) {
                pauseTimeSec += e.durationSec;
            } else if (e.eventType === 'ACW_END' && e.durationSec) {
                wrapupTimeSec += e.durationSec;
            }
        }
        if (openLoginAt !== null) {
            // Still logged in — count up to now (capped to the rollup day end).
            loginDurationSec += Math.max(0, Math.round((Date.now() - openLoginAt) / 1000));
        }

        const avgHandlingTimeSec = handlingCount > 0 ? Math.round(handlingSum / handlingCount) : null;
        const idleTimeSec = Math.max(0, loginDurationSec - busyTimeSec - pauseTimeSec - wrapupTimeSec);

        return { loginDurationSec, busyTimeSec, pauseTimeSec, wrapupTimeSec, idleTimeSec, avgHandlingTimeSec };
    }

    // AgentSession fields map: our `*Sec` → platform `*S`, `sessionDate` → `date`.
    private async upsertSession(
        agentUuid: string,
        sessionDate: string,
        totals: { loginDurationSec: number; busyTimeSec: number; pauseTimeSec: number; wrapupTimeSec: number; idleTimeSec: number; avgHandlingTimeSec: number | null },
    ): Promise<void> {
        const existing = await this.platform.query<any>(
            `{ agentSessions(first: 1, filter: { agentId: { eq: "${agentUuid}" }, date: { eq: "${sessionDate}" } }) { edges { node { id } } } }`,
        );
        const existingId = existing?.agentSessions?.edges?.[0]?.node?.id;

        const data: Record<string, any> = {
            loginDurationS: totals.loginDurationSec,
            busyTimeS: totals.busyTimeSec,
            pauseTimeS: totals.pauseTimeSec,
            wrapupTimeS: totals.wrapupTimeSec,
            idleTimeS: totals.idleTimeSec,
            source: 'COMPUTED',
            lastSyncedAt: new Date().toISOString(),
        };
        if (totals.avgHandlingTimeSec !== null) data.avgHandlingTimeS = totals.avgHandlingTimeSec;

        if (existingId) {
            await this.platform.query<any>(
                `mutation($id: UUID!, $data: AgentSessionUpdateInput!) { updateAgentSession(id: $id, data: $data) { id } }`,
                { id: existingId, data },
            );
        } else {
            await this.platform.query<any>(
                `mutation($data: AgentSessionCreateInput!) { createAgentSession(data: $data) { id } }`,
                { data: { ...data, name: `Session ${sessionDate}`, agentId: agentUuid, date: sessionDate } },
            );
        }
    }
}