import { eq, and, sql, lt, gt } from "drizzle-orm";
import { drizzle } from "drizzle-orm/mysql2";
import { 
  InsertUser, 
  users, 
  formations, 
  apprenants, 
  sessions, 
  inscriptions,
  InsertFormation,
  InsertApprenant,
  InsertSession,
  InsertInscription
} from "../drizzle/schema";
import { ENV } from './_core/env';

let _db: ReturnType<typeof drizzle> | null = null;

// Lazily create the drizzle instance so local tooling can run without a DB.
export async function getDb() {
  if (!_db && process.env.DATABASE_URL) {
    try {
      _db = drizzle(process.env.DATABASE_URL);
    } catch (error) {
      console.warn("[Database] Failed to connect:", error);
      _db = null;
    }
  }
  return _db;
}

export async function upsertUser(user: InsertUser): Promise<void> {
  if (!user.openId) {
    throw new Error("User openId is required for upsert");
  }

  const db = await getDb();
  if (!db) {
    console.warn("[Database] Cannot upsert user: database not available");
    return;
  }

  try {
    const values: InsertUser = {
      openId: user.openId,
    };
    const updateSet: Record<string, unknown> = {};

    const textFields = ["name", "email", "loginMethod"] as const;
    type TextField = (typeof textFields)[number];

    const assignNullable = (field: TextField) => {
      const value = user[field];
      if (value === undefined) return;
      const normalized = value ?? null;
      values[field] = normalized;
      updateSet[field] = normalized;
    };

    textFields.forEach(assignNullable);

    if (user.lastSignedIn !== undefined) {
      values.lastSignedIn = user.lastSignedIn;
      updateSet.lastSignedIn = user.lastSignedIn;
    }
    if (user.role !== undefined) {
      values.role = user.role;
      updateSet.role = user.role;
    } else if (user.openId === ENV.ownerOpenId) {
      values.role = 'admin';
      updateSet.role = 'admin';
    }

    if (!values.lastSignedIn) {
      values.lastSignedIn = new Date();
    }

    if (Object.keys(updateSet).length === 0) {
      updateSet.lastSignedIn = new Date();
    }

    await db.insert(users).values(values).onDuplicateKeyUpdate({
      set: updateSet,
    });
  } catch (error) {
    console.error("[Database] Failed to upsert user:", error);
    throw error;
  }
}

export async function getUserByOpenId(openId: string) {
  const db = await getDb();
  if (!db) {
    console.warn("[Database] Cannot get user: database not available");
    return undefined;
  }

  const result = await db.select().from(users).where(eq(users.openId, openId)).limit(1);

  return result.length > 0 ? result[0] : undefined;
}

// ===== FORMATIONS =====

export async function getAllFormations() {
  const db = await getDb();
  if (!db) return [];
  return db.select().from(formations).orderBy(formations.createdAt);
}

export async function getFormationById(id: number) {
  const db = await getDb();
  if (!db) return undefined;
  const result = await db.select().from(formations).where(eq(formations.id, id)).limit(1);
  return result[0];
}

export async function getFormationByLien(lien: string) {
  const db = await getDb();
  if (!db) return undefined;
  const result = await db.select().from(formations).where(eq(formations.lienUnique, lien)).limit(1);
  return result[0];
}

export async function createFormation(data: InsertFormation) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  const result = await db.insert(formations).values(data);
  return result;
}

export async function updateFormation(id: number, data: Partial<InsertFormation>) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.update(formations).set(data).where(eq(formations.id, id));
}

export async function deleteFormation(id: number) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.delete(formations).where(eq(formations.id, id));
}

// ===== APPRENANTS =====

export async function getAllApprenants() {
  const db = await getDb();
  if (!db) return [];
  return db.select().from(apprenants).orderBy(apprenants.nom, apprenants.prenom);
}

export async function getApprenantById(id: number) {
  const db = await getDb();
  if (!db) return undefined;
  const result = await db.select().from(apprenants).where(eq(apprenants.id, id)).limit(1);
  return result[0];
}

export async function getApprenantByEmail(email: string) {
  const db = await getDb();
  if (!db) return undefined;
  const result = await db.select().from(apprenants).where(eq(apprenants.email, email)).limit(1);
  return result[0];
}

export async function createApprenant(data: InsertApprenant) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  const result = await db.insert(apprenants).values(data);
  return result;
}

export async function updateApprenant(id: number, data: Partial<InsertApprenant>) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.update(apprenants).set(data).where(eq(apprenants.id, id));
}

export async function deleteApprenant(id: number) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.delete(apprenants).where(eq(apprenants.id, id));
}

// ===== SESSIONS =====

export async function getAllSessions() {
  const db = await getDb();
  if (!db) return [];
  return db.select().from(sessions).orderBy(sessions.dateDebut);
}

export async function getSessionsByFormation(formationId: number) {
  const db = await getDb();
  if (!db) return [];
  return db.select().from(sessions).where(eq(sessions.formationId, formationId)).orderBy(sessions.dateDebut);
}

export async function getSessionById(id: number) {
  const db = await getDb();
  if (!db) return undefined;
  const result = await db.select().from(sessions).where(eq(sessions.id, id)).limit(1);
  return result[0];
}

export async function createSession(data: InsertSession) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  const result = await db.insert(sessions).values(data);
  return result;
}

export async function updateSession(id: number, data: Partial<InsertSession>) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.update(sessions).set(data).where(eq(sessions.id, id));
}

export async function deleteSession(id: number) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.delete(sessions).where(eq(sessions.id, id));
}

// ===== INSCRIPTIONS =====

export async function getInscriptionsBySession(sessionId: number) {
  const db = await getDb();
  if (!db) return [];
  
  const result = await db
    .select({
      inscription: inscriptions,
      apprenant: apprenants,
    })
    .from(inscriptions)
    .leftJoin(apprenants, eq(inscriptions.apprenantId, apprenants.id))
    .where(eq(inscriptions.sessionId, sessionId))
    .orderBy(inscriptions.dateInscription);
  
  return result;
}

export async function getInscriptionsByApprenant(apprenantId: number) {
  const db = await getDb();
  if (!db) return [];
  
  const result = await db
    .select({
      inscription: inscriptions,
      session: sessions,
      formation: formations,
    })
    .from(inscriptions)
    .leftJoin(sessions, eq(inscriptions.sessionId, sessions.id))
    .leftJoin(formations, eq(sessions.formationId, formations.id))
    .where(eq(inscriptions.apprenantId, apprenantId))
    .orderBy(inscriptions.dateInscription);
  
  return result;
}

export async function getInscriptionByApprenantAndSession(apprenantId: number, sessionId: number) {
  const db = await getDb();
  if (!db) return undefined;
  
  const result = await db
    .select()
    .from(inscriptions)
    .where(and(
      eq(inscriptions.apprenantId, apprenantId),
      eq(inscriptions.sessionId, sessionId)
    ))
    .limit(1);
  
  return result[0];
}

export async function countInscriptionsConfirmees(sessionId: number) {
  const db = await getDb();
  if (!db) return 0;
  
  const result = await db
    .select({ count: sql<number>`count(*)` })
    .from(inscriptions)
    .where(and(
      eq(inscriptions.sessionId, sessionId),
      eq(inscriptions.statut, "confirmee")
    ));
  
  return result[0]?.count || 0;
}

export async function createInscription(data: InsertInscription) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  const result = await db.insert(inscriptions).values(data);
  return result;
}

export async function updateInscription(id: number, data: Partial<InsertInscription>) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.update(inscriptions).set(data).where(eq(inscriptions.id, id));
}

export async function deleteInscription(id: number) {
  const db = await getDb();
  if (!db) throw new Error("Database not available");
  await db.delete(inscriptions).where(eq(inscriptions.id, id));
}

export async function getSessionsAvecInscriptions(formationId: number) {
  const db = await getDb();
  if (!db) return [];
  
  const result = await db
    .select({
      session: sessions,
      nbInscrits: sql<number>`count(CASE WHEN ${inscriptions.statut} = 'confirmee' THEN 1 END)`,
    })
    .from(sessions)
    .leftJoin(inscriptions, eq(sessions.id, inscriptions.sessionId))
    .where(eq(sessions.formationId, formationId))
    .groupBy(sessions.id)
    .orderBy(sessions.dateDebut);
  
  return result;
}