// P4 Tasks (AK-P4b) — lightweight cross-cutting task module.
//
// AD-21: one self-contained schema file per module. `tenantId` /
// `createdByUserId` / `assignedToUserId` / `assignedToGroupId` are intentionally
// BARE String scalars (no `@relation`) so this file has zero merge-conflict
// surface against `core.prisma`/`accounts.prisma` (no back-relation fields on
// Tenant/User/Group needed). Referential integrity is carried by app-level
// scoping (taskService + taskAccess) plus the RLS policies from the merge
// migration (see local/AK-P4b-merge-migration.sql).
//
// Assignment rule (DoD 2): a task is assigned to EXACTLY ONE of a user or a
// group; default = creator. Enforced in the service layer and by a DB CHECK
// constraint (num_nonnulls(...) = 1) added in the merge migration.
//
// Entity linking: the primary "this task is about X" association lives inline on
// the Task (`linkedEntityType`/`linkedEntityId`). The generic, reusable
// cross-entity link table is `EntityLink` (entityLinks.prisma, Gate W1); wiring
// tasks to concrete CRM entities happens in P6.

enum TaskStatus {
  open
  in_progress
  blocked
  done
  cancelled
}

enum TaskPriority {
  low
  normal
  high
  urgent
}

enum TaskSource {
  manual
  chat
  form_submission
  automation
  api
}

enum TaskEntityType {
  contact
  company
  lead
  deal
  project
  user
  order
  appointment
}

/// A task, scoped per tenant. Soft-delete via `archivedAt` (archive flag). A
/// completed task (`status = done`, `completedAt` set) is auto-archived 30 days
/// later by a maintenance cron.
model Task {
  id                String          @id @default(cuid())
  createdAt         DateTime        @default(now())
  updatedAt         DateTime        @updatedAt
  tenantId          String
  createdByUserId   String
  title             String
  description       String? // markdown
  status            TaskStatus      @default(open)
  priority          TaskPriority    @default(normal)
  deadline          DateTime?
  // Assignment: EXACTLY ONE of user/group (DB CHECK in merge migration);
  // default = creator (filled by the service when neither is provided).
  assignedToUserId  String?
  assignedToGroupId String?
  // Inline primary entity association (polymorphic) — "this task is about X".
  linkedEntityType  TaskEntityType?
  linkedEntityId    String?
  source            TaskSource      @default(manual)
  sourceRef         String? // marker/link back to origin (chat msg / form submission / automation run)
  completedAt       DateTime?
  isDemoData        Boolean         @default(false)
  archivedAt        DateTime?

  watchers TaskWatcher[]

  @@index([tenantId, archivedAt, status, deadline])
  @@index([tenantId, assignedToUserId])
  @@index([tenantId, assignedToGroupId])
  @@index([tenantId, createdByUserId])
  @@index([tenantId, linkedEntityType, linkedEntityId])
  @@index([tenantId, status, completedAt]) // for the 30-day archive sweep
}

/// A user watching a task (M:N). Watchers receive reminder notifications in
/// addition to the assignee.
model TaskWatcher {
  id        String   @id @default(cuid())
  createdAt DateTime @default(now())
  tenantId  String
  taskId    String
  userId    String

  task Task @relation(fields: [taskId], references: [id], onDelete: Cascade)

  @@unique([taskId, userId])
  @@index([tenantId, userId])
}