import { sql, eq, and, ne } from "drizzle-orm";
import { db } from "@/lib/db/client";
import { sessions, sessionDevices, sessionEvents, devices } from "@/lib/db/schema";

export async function getSessionsSummary() {
  const [totals] = await db
    .select({
      count: sql<number>`count(*)`,
      totalDurationMs: sql<number>`coalesce(sum(${sessions.durationMs}), 0)`,
      avgDurationMs: sql<number>`coalesce(avg(${sessions.durationMs}), 0)`,
      // How many times sessions have been replayed - replaying itself creates no
      // session of its own, it just bumps the source session's playCount.
      totalReplays: sql<number>`coalesce(sum(${sessions.playCount}), 0)`,
    })
    .from(sessions)
    .where(eq(sessions.status, "completed"));

  const durationPerDevice = await db
    .select({
      deviceId: devices.id,
      displayName: devices.displayName,
      bleName: devices.bleName,
      totalActiveMs: sql<number>`coalesce(sum(coalesce(${sessionDevices.disconnectedAt}, ${sessionDevices.connectedAt}) - ${sessionDevices.connectedAt}), 0)`,
    })
    .from(sessionDevices)
    .innerJoin(devices, eq(sessionDevices.deviceId, devices.id))
    .groupBy(devices.id);

  return { ...totals, durationPerDevice };
}

export async function getSessionTimeline(sessionId: number, bucketMs = 1000) {
  // Reuse the same expression object (not a `sql`bucket`` alias reference)
  // in groupBy/orderBy - drizzle doesn't emit a literal `AS bucket` that
  // SQLite's GROUP BY/ORDER BY could resolve a bare "bucket" identifier
  // against, so referencing it by name causes "no such column: bucket".
  const bucket = sql<number>`(${sessionEvents.tsMs} / ${bucketMs}) * ${bucketMs}`;

  return db
    .select({
      bucket,
      sessionDeviceId: sessionEvents.sessionDeviceId,
      slotLabel: sessionDevices.slotLabel,
      avgValue: sql<number>`avg(${sessionEvents.value})`,
      maxValue: sql<number>`max(${sessionEvents.value})`,
    })
    .from(sessionEvents)
    .innerJoin(sessionDevices, eq(sessionEvents.sessionDeviceId, sessionDevices.id))
    .where(and(eq(sessionEvents.sessionId, sessionId), ne(sessionEvents.commandType, "stop")))
    .groupBy(bucket, sessionEvents.sessionDeviceId)
    .orderBy(bucket);
}

export async function getDeviceUsageStats() {
  return db
    .select({
      deviceId: devices.id,
      displayName: devices.displayName,
      bleName: devices.bleName,
      sessionCount: sql<number>`count(distinct ${sessionDevices.sessionId})`,
      totalActiveMs: sql<number>`coalesce(sum(coalesce(${sessionDevices.disconnectedAt}, ${sessionDevices.connectedAt}) - ${sessionDevices.connectedAt}), 0)`,
      lastUsedAt: sql<number | null>`max(${sessionDevices.connectedAt})`,
    })
    .from(devices)
    .leftJoin(sessionDevices, eq(sessionDevices.deviceId, devices.id))
    .groupBy(devices.id);
}

export async function getDeviceCommandCounts() {
  return db
    .select({
      deviceId: devices.id,
      commandCount: sql<number>`count(${sessionEvents.id})`,
    })
    .from(devices)
    .leftJoin(sessionDevices, eq(sessionDevices.deviceId, devices.id))
    .leftJoin(sessionEvents, eq(sessionEvents.sessionDeviceId, sessionDevices.id))
    .groupBy(devices.id);
}