import {
  BusinessRuleError,
  VersionedAggregateRoot,
  assertThat,
} from '@task-stream/api/shared/domain';
import { IssueAssignedEvent } from '../events/issue-assigned.event';
import { IssueCreatedEvent } from '../events/issue-created.event';
import { IssueLinkedEvent } from '../events/issue-linked.event';
import { IssueReleaseChangedEvent } from '../events/issue-release-changed.event';
import { IssueStatusChangedEvent } from '../events/issue-status-changed.event';
import { IssueUnlinkedEvent } from '../events/issue-unlinked.event';
import { IssueUpdatedEvent } from '../events/issue-updated.event';
import {
  IssueArea,
  IssueLinkType,
  IssuePriority,
  IssueStatus,
  IssueType,
} from './issue.enums';
import { IssueWorkflow } from './issue-workflow';

export interface IssueLink {
  type: IssueLinkType;
  targetIssueId: string;
  targetKey: string;
}

/** Fields editable after creation. */
export interface IssueDetails {
  title?: string;
  description?: string | null;
  type?: IssueType;
  area?: IssueArea | null;
  priority?: IssuePriority;
  labels?: string[];
  figmaUrl?: string | null;
  storyPoints?: number | null;
  dueDate?: string | null;
}

/** Data of a ticket (what IssueCreatedEvent carries). */
export interface IssueProps {
  id: string;
  projectId: string;
  number: number;
  key: string;
  type: IssueType;
  area: IssueArea | null;
  title: string;
  description: string | null;
  status: IssueStatus;
  priority: IssuePriority;
  reporterId: string;
  assigneeId: string | null;
  releaseId: string | null;
  labels: string[];
  figmaUrl: string | null;
  storyPoints: number | null;
  dueDate: string | null;
  links: IssueLink[];
  createdAt: string;
  updatedAt: string;
}

/**
 * A ticket: bug, feature, UI change, task or QA. Event-sourced: create it
 * with IssueFactory, load it with the AggregateRehydrator.
 */
export class Issue extends VersionedAggregateRoot implements IssueProps {
  public projectId!: string;
  public number!: number;
  public key!: string;
  public type!: IssueType;
  public area: IssueArea | null = null;
  public title!: string;
  public description: string | null = null;
  public status: IssueStatus = IssueStatus.BACKLOG;
  public priority: IssuePriority = IssuePriority.MEDIUM;
  public reporterId!: string;
  public assigneeId: string | null = null;
  public releaseId: string | null = null;
  public labels: string[] = [];
  public figmaUrl: string | null = null;
  public storyPoints: number | null = null;
  public dueDate: string | null = null;
  public links: IssueLink[] = [];
  public createdAt!: string;
  public updatedAt!: string;

  constructor(id: string) {
    super();
    this.id = id;
  }

  updateDetails(actorId: string, changes: IssueDetails): void {
    const next = normalizeIssueDetails(changes);
    const patch: IssueDetails = {};
    for (const field of Object.keys(next) as (keyof IssueDetails)[]) {
      const value = next[field];
      if (value === undefined) continue;
      if (JSON.stringify(value) === JSON.stringify(this[field])) continue;
      (patch as Record<string, unknown>)[field] = value;
    }
    if (patch.title !== undefined)
      assertThat(patch.title.length > 0, 'Issue title is required');
    if (Object.keys(patch).length === 0) return;
    this.apply(new IssueUpdatedEvent(actorId, this.id, this.projectId, patch));
  }

  changeStatus(actorId: string, to: IssueStatus, reason?: string | null): void {
    const from = this.status;
    if (from === to) return;
    if (!IssueWorkflow.canTransition(from, to)) {
      throw new BusinessRuleError(
        `Cannot move ${this.key} from ${from} to ${to}. Allowed: ${IssueWorkflow.allowedFrom(from).join(', ')}`,
      );
    }
    const trimmedReason = reason?.trim() || null;
    if (IssueWorkflow.requiresReason(to) && !trimmedReason) {
      throw new BusinessRuleError(
        `A reason is required to move ${this.key} to ${to}`,
      );
    }
    this.apply(
      new IssueStatusChangedEvent(
        actorId,
        this.id,
        this.projectId,
        from,
        to,
        trimmedReason,
      ),
    );
  }

  /** @param assigneeId null to unassign */
  assign(actorId: string, assigneeId: string | null): void {
    if (this.assigneeId === assigneeId) return;
    this.apply(
      new IssueAssignedEvent(
        actorId,
        this.id,
        this.projectId,
        assigneeId,
        this.assigneeId,
      ),
    );
  }

  linkTo(
    actorId: string,
    type: IssueLinkType,
    target: { id: string; key: string },
  ): void {
    if (target.id === this.id)
      throw new BusinessRuleError('An issue cannot be linked to itself');
    if (
      this.links.some((l) => l.type === type && l.targetIssueId === target.id)
    ) {
      throw new BusinessRuleError(`${this.key} already ${type} ${target.key}`);
    }
    this.apply(
      new IssueLinkedEvent(actorId, this.id, this.projectId, {
        type,
        targetIssueId: target.id,
        targetKey: target.key,
      }),
    );
  }

  unlink(actorId: string, type: IssueLinkType, targetIssueId: string): void {
    const link = this.links.find(
      (l) => l.type === type && l.targetIssueId === targetIssueId,
    );
    if (!link) throw new BusinessRuleError('Link not found');
    this.apply(
      new IssueUnlinkedEvent(actorId, this.id, this.projectId, { ...link }),
    );
  }

  /** Moves the ticket in or out of a release (null removes it). */
  setRelease(actorId: string, releaseId: string | null): void {
    if (this.releaseId === releaseId) return;
    this.apply(
      new IssueReleaseChangedEvent(
        actorId,
        this.id,
        this.projectId,
        releaseId,
        this.releaseId,
      ),
    );
  }

  /* ---- State transitions (also replayed by loadFromHistory) ---- */

  onIssueCreatedEvent({ issue }: IssueCreatedEvent): void {
    Object.assign(this, {
      ...issue,
      labels: [...issue.labels],
      links: issue.links.map((l) => ({ ...l })),
    });
  }

  onIssueUpdatedEvent(event: IssueUpdatedEvent): void {
    Object.assign(this, event.changes);
    this.updatedAt = event.occurredAt;
  }

  onIssueStatusChangedEvent(event: IssueStatusChangedEvent): void {
    this.status = event.to;
    this.updatedAt = event.occurredAt;
  }

  onIssueAssignedEvent(event: IssueAssignedEvent): void {
    this.assigneeId = event.assigneeId;
    this.updatedAt = event.occurredAt;
  }

  onIssueLinkedEvent(event: IssueLinkedEvent): void {
    this.links = [...this.links, { ...event.link }];
    this.updatedAt = event.occurredAt;
  }

  onIssueUnlinkedEvent(event: IssueUnlinkedEvent): void {
    this.links = this.links.filter(
      (l) =>
        !(
          l.type === event.link.type &&
          l.targetIssueId === event.link.targetIssueId
        ),
    );
    this.updatedAt = event.occurredAt;
  }

  onIssueReleaseChangedEvent(event: IssueReleaseChangedEvent): void {
    this.releaseId = event.releaseId;
    this.updatedAt = event.occurredAt;
  }
}

/** Trims, deduplicates and validates editable issue fields. */
export function normalizeIssueDetails(details: IssueDetails): IssueDetails {
  const out: IssueDetails = { ...details };
  if (details.title !== undefined) out.title = details.title.trim();
  if (details.description !== undefined)
    out.description = details.description?.trim() || null;
  if (details.labels !== undefined) {
    out.labels = [
      ...new Set(
        details.labels.map((l) => l.trim().toLowerCase()).filter(Boolean),
      ),
    ];
  }
  if (details.figmaUrl !== undefined && details.figmaUrl !== null) {
    const url = details.figmaUrl.trim();
    assertThat(
      /^https:\/\/([\w-]+\.)?figma\.com\//.test(url),
      'figmaUrl must be a figma.com link',
    );
    out.figmaUrl = url;
  }
  if (details.storyPoints !== undefined && details.storyPoints !== null) {
    assertThat(
      Number.isInteger(details.storyPoints) &&
        details.storyPoints >= 0 &&
        details.storyPoints <= 100,
      'storyPoints must be an integer between 0 and 100',
    );
  }
  if (details.dueDate !== undefined && details.dueDate !== null) {
    assertThat(
      !Number.isNaN(Date.parse(details.dueDate)),
      'dueDate must be an ISO date',
    );
  }
  return out;
}