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

export type ResolvedCaller = {
    leadId: string;
    patientId: string;
    firstName: string;
    lastName: string;
    phone: string;
    isNew: boolean; // true if no Lead/Patient exists for this phone
};

@Injectable()
export class CallerResolutionService {
    private readonly logger = new Logger(CallerResolutionService.name);

    constructor(
        private readonly platform: PlatformGraphqlService,
    ) {}

    // Resolve a caller by phone number via indexed platform queries. No
    // cache — every call hits the DB fresh. Cache was previously used to
    // compensate for client-side `leads(first: 200)` scans, but we now
    // filter by phone directly which is O(log n) with the DB index.
    // Cost: ~2 fast queries per resolve; eventual-consistency window = 0.
    async resolve(phone: string, auth: string): Promise<ResolvedCaller> {
        const normalized = phone.replace(/\D/g, '').slice(-10);
        if (normalized.length < 10) {
            throw new Error(`Invalid phone number: ${phone}`);
        }

        // Lookup lead + patient by phone, in parallel.
        const [lead, patient] = await Promise.all([
            this.findLeadByPhone(normalized, auth),
            this.findPatientByPhone(normalized, auth),
        ]);

        let result: ResolvedCaller;

        if (lead && patient) {
            // Both exist — link them if not already linked
            if (!lead.patientId) {
                await this.linkLeadToPatient(lead.id, patient.id, auth);
                this.logger.log(`[RESOLVE] Linked existing lead ${lead.id} → patient ${patient.id}`);
            }
            // PRD: "Returning patient (Y/N) will be taken care of by the system"
            // Patient is recognized on a subsequent contact → mark as RETURNING
            if (patient.patientType === 'NEW') {
                this.upgradeToReturning(patient.id, auth);
            }
            result = {
                leadId: lead.id,
                patientId: patient.id,
                firstName: lead.firstName || patient.firstName,
                lastName: lead.lastName || patient.lastName,
                phone: normalized,
                isNew: false,
            };
        } else if (lead && !patient) {
            // Lead exists, no patient — create patient
            const newPatient = await this.createPatient(lead.firstName, lead.lastName, normalized, auth);
            await this.linkLeadToPatient(lead.id, newPatient.id, auth);
            this.logger.log(`[RESOLVE] Created patient ${newPatient.id} for existing lead ${lead.id}`);
            result = {
                leadId: lead.id,
                patientId: newPatient.id,
                firstName: lead.firstName,
                lastName: lead.lastName,
                phone: normalized,
                isNew: false,
            };
        } else if (!lead && patient) {
            // Patient exists, no lead — create lead
            const newLead = await this.createLead(patient.firstName, patient.lastName, normalized, patient.id, auth);
            this.logger.log(`[RESOLVE] Created lead ${newLead.id} for existing patient ${patient.id}`);
            if (patient.patientType === 'NEW') {
                this.upgradeToReturning(patient.id, auth);
            }
            result = {
                leadId: newLead.id,
                patientId: patient.id,
                firstName: patient.firstName,
                lastName: patient.lastName,
                phone: normalized,
                isNew: false,
            };
        } else {
            // Neither exists — return empty IDs with isNew=true. Caller
            // code is responsible for creating records with the real name
            // they've collected (enquiry form, appointment form, widget,
            // AI tools). This avoids the "Unknown" placeholder cascade:
            // no Lead/Patient is ever written unless we have a real name
            // to attach to it. Missed-call / poller paths that have no
            // name persist the Call record with leadName=phone as the
            // honest snapshot.
            this.logger.log(`[RESOLVE] No existing records for ${normalized} — returning isNew=true`);
            result = {
                leadId: '',
                patientId: '',
                firstName: '',
                lastName: '',
                phone: normalized,
                isNew: true,
            };
        }

        return result;
    }

    // Indexed lookup — platform filters by phone server-side. Matches on
    // the last 10 digits regardless of stored format (+919XXXX / 91XXXX /
    // XXXX / +91-XXXX), via the `like: "%XXXXXXXXXX"` predicate.
    private async findLeadByPhone(phone10: string, auth: string): Promise<{ id: string; firstName: string; lastName: string; patientId: string | null } | null> {
        try {
            const data = await this.platform.queryWithAuth<{ leads: { edges: { node: any }[] } }>(
                `{ leads(first: 1, filter: { contactPhone: { primaryPhoneNumber: { like: "%${phone10}" } } }) { edges { node {
                    id
                    contactName { firstName lastName }
                    patientId
                } } } }`,
                undefined,
                auth,
            );
            const match = data.leads.edges[0]?.node;
            if (!match) return null;
            return {
                id: match.id,
                firstName: match.contactName?.firstName ?? '',
                lastName: match.contactName?.lastName ?? '',
                patientId: match.patientId || null,
            };
        } catch (err: any) {
            this.logger.warn(`[RESOLVE] Lead lookup failed: ${err.message}`);
            return null;
        }
    }

    private async findPatientByPhone(phone10: string, auth: string): Promise<{ id: string; firstName: string; lastName: string; patientType: string | null } | null> {
        try {
            const data = await this.platform.queryWithAuth<{ patients: { edges: { node: any }[] } }>(
                `{ patients(first: 1, filter: { phones: { primaryPhoneNumber: { like: "%${phone10}" } } }) { edges { node {
                    id
                    fullName { firstName lastName }
                    patientType
                } } } }`,
                undefined,
                auth,
            );
            const match = data.patients.edges[0]?.node;
            if (!match) return null;
            return {
                id: match.id,
                firstName: match.fullName?.firstName ?? '',
                lastName: match.fullName?.lastName ?? '',
                patientType: match.patientType ?? null,
            };
        } catch (err: any) {
            this.logger.warn(`[RESOLVE] Patient lookup failed: ${err.message}`);
            return null;
        }
    }

    private async createPatient(firstName: string, lastName: string, phone: string, auth: string): Promise<{ id: string }> {
        const data = await this.platform.queryWithAuth<{ createPatient: { id: string } }>(
            `mutation($data: PatientCreateInput!) { createPatient(data: $data) { id } }`,
            {
                data: {
                    name: `${firstName || 'Unknown'} ${lastName || ''}`.trim(),
                    fullName: { firstName: firstName || 'Unknown', lastName: lastName || '' },
                    phones: { primaryPhoneNumber: `+91${phone}` },
                    patientType: 'NEW',
                },
            },
            auth,
        );
        return data.createPatient;
    }

    private async createLead(firstName: string, lastName: string, phone: string, patientId: string, auth: string): Promise<{ id: string }> {
        const data = await this.platform.queryWithAuth<{ createLead: { id: string } }>(
            `mutation($data: LeadCreateInput!) { createLead(data: $data) { id } }`,
            {
                data: {
                    name: `${firstName} ${lastName}`.trim() || 'Unknown Caller',
                    contactName: { firstName: firstName || 'Unknown', lastName: lastName || '' },
                    contactPhone: { primaryPhoneNumber: `+91${phone}` },
                    source: 'PHONE',
                    status: 'NEW',
                    patientId,
                },
            },
            auth,
        );
        return data.createLead;
    }

    private upgradeToReturning(patientId: string, auth: string): void {
        // Fire-and-forget — don't block caller resolution
        this.platform.queryWithAuth<any>(
            `mutation($id: UUID!, $data: PatientUpdateInput!) { updatePatient(id: $id, data: $data) { id } }`,
            { id: patientId, data: { patientType: 'RETURNING' } },
            auth,
        ).then(() => {
            this.logger.log(`[RESOLVE] Upgraded patient ${patientId} to RETURNING`);
        }).catch(err => {
            this.logger.warn(`[RESOLVE] Failed to upgrade patient type: ${err.message}`);
        });
    }

    private async linkLeadToPatient(leadId: string, patientId: string, auth: string): Promise<void> {
        await this.platform.queryWithAuth<any>(
            `mutation($id: UUID!, $data: LeadUpdateInput!) { updateLead(id: $id, data: $data) { id } }`,
            { id: leadId, data: { patientId } },
            auth,
        );
    }
}