import { and, eq, inArray, isNotNull, isNull, lt, lte, ne, or } from 'drizzle-orm'
import { incidentReference } from '../shared/format.ts'
import type { Config } from './config.ts'
import type { Db } from './db/client.ts'
import { correctiveActions, incidents, users } from './db/schema.ts'
import { addDays, localDate } from './lib/dates.ts'
import type { Mailer } from './mail.ts'

const severityLabel = { low: 'Low', medium: 'Medium', high: 'High', critical: 'Critical' } as const

/** Sends emails in the background so slow mail servers never delay or fail a request. */
export class Notifier {
  private readonly pending = new Set<Promise<void>>()
  private readonly db: Db
  private readonly mailer: Mailer
  private readonly config: Config

  constructor(db: Db, mailer: Mailer, config: Config) {
    this.db = db
    this.mailer = mailer
    this.config = config
  }

  /** Waits for queued emails (tests, shutdown). */
  async flush(): Promise<void> {
    await Promise.all([...this.pending])
  }

  private dispatch(task: () => Promise<void>) {
    const run = task()
      .catch((error) => console.error('[notify] failed:', error))
      .finally(() => this.pending.delete(run))
    this.pending.add(run)
  }

  private link(path: string) {
    return new URL(path, this.config.publicUrl).toString()
  }

  magicLink(email: string, token: string) {
    this.dispatch(() =>
      this.mailer.send({
        to: email,
        subject: 'Your sign-in link',
        text: `Use this link to sign in to Open SafetyLog EHS. It works once and expires in 15 minutes.\n\n${this.link(`/auth/magic?token=${token}`)}\n\nIf you didn't ask for it, you can ignore this email.`,
      }),
    )
  }

  passwordReset(email: string, token: string, invite: { organization: string; invitedBy: string } | null) {
    const link = this.link(`/auth/reset?token=${token}`)
    this.dispatch(() =>
      this.mailer.send(
        invite
          ? {
              to: email,
              subject: `You've been invited to ${invite.organization} on Open SafetyLog EHS`,
              text: `${invite.invitedBy} added you to ${invite.organization}'s safety workspace.\n\nSet your password to get started (link valid for 7 days):\n\n${link}`,
            }
          : {
              to: email,
              subject: 'Reset your password',
              text: `Use this link to choose a new password. It works once and expires in 1 hour.\n\n${link}\n\nIf you didn't ask for it, you can ignore this email; your password hasn't changed.`,
            },
      ),
    )
  }

  /** Alerts safety managers and admins about high and critical reports. */
  incidentReported(incidentId: string) {
    this.dispatch(async () => {
      const [incident] = await this.db.select().from(incidents).where(eq(incidents.id, incidentId))
      if (!incident || (incident.severity !== 'high' && incident.severity !== 'critical')) return
      const recipients = await this.db
        .select({ email: users.email })
        .from(users)
        .where(
          and(
            eq(users.organizationId, incident.organizationId),
            eq(users.active, true),
            inArray(users.role, ['safety_manager', 'admin']),
            incident.reporterId ? ne(users.id, incident.reporterId) : undefined,
          ),
        )
      const reference = incidentReference(incident.number)
      for (const { email } of recipients) {
        await this.mailer.send({
          to: email,
          subject: `[${severityLabel[incident.severity]}] ${reference}: ${incident.title}`,
          text: `A ${severityLabel[incident.severity].toLowerCase()}-severity incident was reported.\n\n${reference}: ${incident.title}\nOccurred: ${incident.occurredAt.toLocaleString('en-US')}\n\n${this.link(`/incidents/${incident.number}`)}`,
        })
      }
    })
  }

  actionAssigned(actionId: string, assignedBy: string) {
    this.dispatch(async () => {
      const [row] = await this.db
        .select({ action: correctiveActions, email: users.email, number: incidents.number, incidentTitle: incidents.title })
        .from(correctiveActions)
        .innerJoin(users, eq(users.id, correctiveActions.assigneeId))
        .innerJoin(incidents, eq(incidents.id, correctiveActions.incidentId))
        .where(and(eq(correctiveActions.id, actionId), eq(users.active, true)))
      if (!row) return
      const due = row.action.dueDate ? `Due: ${row.action.dueDate}\n` : ''
      await this.mailer.send({
        to: row.email,
        subject: `Action assigned: ${row.action.title}`,
        text: `${assignedBy} assigned you a corrective action on ${incidentReference(row.number)} (${row.incidentTitle}).\n\n${row.action.title}\n${due}\n${this.link(`/incidents/${row.number}`)}`,
      })
    })
  }

  /**
   * Emails each assignee a digest of open actions due tomorrow or earlier, at most once a day per action.
   * Returns how many emails were queued.
   */
  async sendDueReminders(today = localDate()): Promise<number> {
    const rows = await this.db
      .select({ action: correctiveActions, email: users.email, number: incidents.number })
      .from(correctiveActions)
      .innerJoin(users, eq(users.id, correctiveActions.assigneeId))
      .innerJoin(incidents, eq(incidents.id, correctiveActions.incidentId))
      .where(
        and(
          inArray(correctiveActions.status, ['open', 'in_progress']),
          eq(users.active, true),
          isNotNull(correctiveActions.dueDate),
          lte(correctiveActions.dueDate, addDays(today, 1)),
          or(isNull(correctiveActions.reminderSentOn), lt(correctiveActions.reminderSentOn, today)),
        ),
      )
    const byEmail = Map.groupBy(rows, (row) => row.email)
    for (const [email, items] of byEmail) {
      const lines = items.map(({ action, number }) => {
        const when = action.dueDate! < today ? `OVERDUE since ${action.dueDate}` : action.dueDate === today ? 'due today' : 'due tomorrow'
        return `- ${action.title} (${incidentReference(number)}), ${when}\n  ${this.link(`/incidents/${number}`)}`
      })
      const overdue = items.filter(({ action }) => action.dueDate! < today).length
      this.dispatch(() =>
        this.mailer.send({
          to: email,
          subject: overdue ? `${overdue} overdue corrective action${overdue === 1 ? '' : 's'}` : 'Corrective actions due soon',
          text: `These corrective actions assigned to you need attention:\n\n${lines.join('\n')}\n\nAll your actions: ${this.link('/actions')}`,
        }),
      )
    }
    if (rows.length) {
      await this.db
        .update(correctiveActions)
        .set({ reminderSentOn: today })
        .where(inArray(correctiveActions.id, rows.map(({ action }) => action.id)))
    }
    return byEmail.size
  }
}