import {
  BusinessRuleError,
  ValidationError,
  assertThat,
} from '@task-stream/api/shared/domain';
import { IssueArea, IssueStatus as S, IssueType } from '../issue/issue.enums';

/**
 * What a status means, whatever it is called in each project: it keeps
 * releases ("everything finished"), "waiting for QA" and statistics working
 * with custom statuses.
 */
export enum StatusCategory {
  TODO = 'TODO',
  IN_PROGRESS = 'IN_PROGRESS',
  QA = 'QA',
  DONE = 'DONE',
  CANCELLED = 'CANCELLED',
}

/** Colour tokens the web app knows (light and dark). */
export const SETTING_COLORS = [
  'slate',
  'stone',
  'violet',
  'blue',
  'sky',
  'teal',
  'green',
  'amber',
  'orange',
  'red',
  'pink',
] as const;
export type SettingColor = (typeof SETTING_COLORS)[number];

/** Icons a ticket type can use (registered in the web app). */
export const TYPE_ICONS = [
  'bug',
  'feature',
  'palette',
  'task',
  'qa',
  'flag',
  'star-fill',
  'rocket',
  'document',
  'light-bulb',
  'key',
  'support',
] as const;
export type TypeIcon = (typeof TYPE_ICONS)[number];

export interface WorkflowStatus {
  /** Stable id stored on tickets, e.g. IN_REVIEW. */
  id: string;
  name: string;
  category: StatusCategory;
  color: SettingColor;
  /** Entering it needs a reason (kept in the history). */
  requiresReason: boolean;
  /** Archived: no new tickets or transitions into it; existing ones keep it. */
  archived: boolean;
  /**
   * Work-in-progress limit: how many tickets the column should hold at most
   * (null: no limit). A warning, not a lock: the board flags a full column.
   */
  wipLimit?: number | null;
}

export interface IssueTypeOption {
  id: string;
  name: string;
  icon: TypeIcon;
  color: SettingColor;
  archived: boolean;
}

export interface AreaOption {
  id: string;
  name: string;
  archived: boolean;
}

/** Per-project configuration of the tracker. */
export interface ProjectSettings {
  /** In board order. New tickets start in the first active TODO status. */
  statuses: WorkflowStatus[];
  /** Allowed moves: status id → status ids it can go to. */
  transitions: Record<string, string[]>;
  issueTypes: IssueTypeOption[];
  areas: AreaOption[];
}

const status = (
  id: string,
  name: string,
  category: StatusCategory,
  color: SettingColor,
  requiresReason = false,
): WorkflowStatus => ({
  id,
  name,
  category,
  color,
  requiresReason,
  archived: false,
});

/** What every project starts with (and what projects created before settings had). */
export const DEFAULT_PROJECT_SETTINGS: ProjectSettings = {
  statuses: [
    status(S.BACKLOG, 'Backlog', StatusCategory.TODO, 'stone'),
    status(S.TODO, 'Por hacer', StatusCategory.TODO, 'slate'),
    status(S.IN_PROGRESS, 'En curso', StatusCategory.IN_PROGRESS, 'violet'),
    status(S.IN_REVIEW, 'En revisión', StatusCategory.IN_PROGRESS, 'blue'),
    status(S.READY_FOR_QA, 'Listo para QA', StatusCategory.QA, 'amber'),
    status(S.IN_QA, 'En QA', StatusCategory.QA, 'orange'),
    status(S.QA_FAILED, 'QA fallido', StatusCategory.IN_PROGRESS, 'red', true),
    status(S.DONE, 'Hecho', StatusCategory.DONE, 'green'),
    status(S.CANCELLED, 'Cancelado', StatusCategory.CANCELLED, 'stone', true),
  ],
  // QA is a first-class step: READY_FOR_QA → IN_QA → DONE | QA_FAILED → IN_PROGRESS.
  transitions: {
    [S.BACKLOG]: [S.TODO, S.IN_PROGRESS, S.CANCELLED],
    [S.TODO]: [S.BACKLOG, S.IN_PROGRESS, S.CANCELLED],
    [S.IN_PROGRESS]: [S.TODO, S.IN_REVIEW, S.READY_FOR_QA, S.CANCELLED],
    [S.IN_REVIEW]: [S.IN_PROGRESS, S.READY_FOR_QA, S.DONE],
    [S.READY_FOR_QA]: [S.IN_QA, S.IN_PROGRESS],
    [S.IN_QA]: [S.DONE, S.QA_FAILED],
    [S.QA_FAILED]: [S.IN_PROGRESS, S.TODO],
    [S.DONE]: [S.TODO, S.IN_PROGRESS],
    [S.CANCELLED]: [S.BACKLOG],
  },
  issueTypes: [
    {
      id: IssueType.BUG,
      name: 'Bug',
      icon: 'bug',
      color: 'red',
      archived: false,
    },
    {
      id: IssueType.FEATURE,
      name: 'Feature',
      icon: 'feature',
      color: 'violet',
      archived: false,
    },
    {
      id: IssueType.UI_CHANGE,
      name: 'Cambio de UI',
      icon: 'palette',
      color: 'pink',
      archived: false,
    },
    {
      id: IssueType.TASK,
      name: 'Tarea',
      icon: 'task',
      color: 'slate',
      archived: false,
    },
    {
      id: IssueType.QA,
      name: 'QA',
      icon: 'qa',
      color: 'amber',
      archived: false,
    },
  ],
  areas: [
    { id: IssueArea.FRONTEND, name: 'Frontend', archived: false },
    { id: IssueArea.BACKEND, name: 'Backend', archived: false },
    { id: IssueArea.MOBILE, name: 'Mobile', archived: false },
    { id: IssueArea.QA, name: 'QA', archived: false },
    { id: IssueArea.DESIGN, name: 'Diseño', archived: false },
    { id: IssueArea.DEVOPS, name: 'DevOps', archived: false },
  ],
};

export function defaultProjectSettings(): ProjectSettings {
  return structuredClone(DEFAULT_PROJECT_SETTINGS);
}

const ID = /^[A-Z][A-Z0-9_]{0,29}$/;
const FINISHED = [StatusCategory.DONE, StatusCategory.CANCELLED];

/** Read-only view of a project's workflow, used by tickets and queries. */
export class ProjectWorkflow {
  constructor(readonly settings: ProjectSettings) {}

  static default(): ProjectWorkflow {
    return new ProjectWorkflow(DEFAULT_PROJECT_SETTINGS);
  }

  status(id: string): WorkflowStatus | undefined {
    return this.settings.statuses.find((s) => s.id === id);
  }

  /** Most tickets the status should hold (null: no limit). */
  wipLimit(id: string): number | null {
    return this.status(id)?.wipLimit ?? null;
  }

  /** Name to show, also for ids no longer configured. */
  statusName(id: string): string {
    return (
      this.status(id)?.name ??
      DEFAULT_PROJECT_SETTINGS.statuses.find((s) => s.id === id)?.name ??
      id
    );
  }

  typeName(id: string): string {
    return (
      this.settings.issueTypes.find((t) => t.id === id)?.name ??
      DEFAULT_PROJECT_SETTINGS.issueTypes.find((t) => t.id === id)?.name ??
      id
    );
  }

  areaName(id: string): string {
    return (
      this.settings.areas.find((a) => a.id === id)?.name ??
      DEFAULT_PROJECT_SETTINGS.areas.find((a) => a.id === id)?.name ??
      id
    );
  }

  categoryOf(id: string): StatusCategory {
    return (
      this.status(id)?.category ??
      DEFAULT_PROJECT_SETTINGS.statuses.find((s) => s.id === id)?.category ??
      StatusCategory.TODO
    );
  }

  isFinished(id: string): boolean {
    return FINISHED.includes(this.categoryOf(id));
  }

  /** Where new tickets start: the first active status of category TODO. */
  initialStatus(): string {
    const initial = this.settings.statuses.find(
      (s) => !s.archived && s.category === StatusCategory.TODO,
    );
    if (!initial)
      throw new BusinessRuleError('The project has no active starting status');
    return initial.id;
  }

  /** Active statuses a ticket can move to from `from`. */
  allowedFrom(from: string): string[] {
    return (this.settings.transitions[from] ?? []).filter(
      (to) => this.status(to) && !this.status(to)?.archived,
    );
  }

  canTransition(from: string, to: string): boolean {
    return this.allowedFrom(from).includes(to);
  }

  requiresReason(id: string): boolean {
    return this.status(id)?.requiresReason ?? false;
  }

  assertActiveType(id: string): void {
    const type = this.settings.issueTypes.find((t) => t.id === id);
    if (!type) throw new ValidationError(`Unknown ticket type ${id}`);
    if (type.archived)
      throw new BusinessRuleError(`Ticket type ${type.name} is archived`);
  }

  assertActiveArea(id: string | null | undefined): void {
    if (id === null || id === undefined) return;
    const area = this.settings.areas.find((a) => a.id === id);
    if (!area) throw new ValidationError(`Unknown area ${id}`);
    if (area.archived)
      throw new BusinessRuleError(`Area ${area.name} is archived`);
  }
}

/**
 * Checks and normalises new settings against the previous ones. Values can be
 * added, renamed, reordered or archived, never deleted: tickets, history and
 * statistics keep referring to them.
 */
export function validateProjectSettings(
  next: ProjectSettings,
  previous: ProjectSettings,
): ProjectSettings {
  const statuses = next.statuses.map((s) => ({
    id: normId(s.id),
    name: normName(s.name),
    category: s.category,
    color: s.color,
    requiresReason: !!s.requiresReason,
    archived: !!s.archived,
    // Only when set: settings saved unchanged must compare equal.
    ...(s.wipLimit != null ? { wipLimit: s.wipLimit } : {}),
  }));
  const issueTypes = next.issueTypes.map((t) => ({
    id: normId(t.id),
    name: normName(t.name),
    icon: t.icon,
    color: t.color,
    archived: !!t.archived,
  }));
  const areas = next.areas.map((a) => ({
    id: normId(a.id),
    name: normName(a.name),
    archived: !!a.archived,
  }));

  for (const [label, list, before] of [
    ['estado', statuses, previous.statuses],
    ['tipo', issueTypes, previous.issueTypes],
    ['área', areas, previous.areas],
  ] as const) {
    const ids = list.map((item) => item.id);
    const duplicate = ids.find((id, i) => ids.indexOf(id) !== i);
    assertThat(!duplicate, `Hay dos ${label}s con el id ${duplicate}`);
    const removed = before.find((item) => !ids.includes(item.id));
    if (removed) {
      throw new BusinessRuleError(
        `No se puede eliminar el ${label} «${removed.name}»: archívalo para que no se use más`,
      );
    }
  }

  for (const s of statuses) {
    assertThat(
      Object.values(StatusCategory).includes(s.category),
      `Categoría no válida en el estado ${s.name}`,
    );
    assertThat(
      SETTING_COLORS.includes(s.color),
      `Color no válido en el estado ${s.name}`,
    );
    assertThat(
      s.wipLimit === undefined ||
        (Number.isInteger(s.wipLimit) && s.wipLimit >= 1 && s.wipLimit <= 999),
      `El límite WIP del estado ${s.name} tiene que ser un número entre 1 y 999`,
    );
  }
  for (const t of issueTypes) {
    assertThat(
      TYPE_ICONS.includes(t.icon),
      `Icono no válido en el tipo ${t.name}`,
    );
    assertThat(
      SETTING_COLORS.includes(t.color),
      `Color no válido en el tipo ${t.name}`,
    );
  }
  const active = statuses.filter((s) => !s.archived);
  assertThat(
    active.some((s) => s.category === StatusCategory.TODO),
    'Hace falta al menos un estado activo «pendiente» donde empiecen los tickets',
  );
  assertThat(
    active.some((s) => s.category === StatusCategory.DONE),
    'Hace falta al menos un estado activo «hecho»',
  );
  assertThat(
    issueTypes.some((t) => !t.archived),
    'Hace falta al menos un tipo de ticket activo',
  );

  const known = new Set(statuses.map((s) => s.id));
  const transitions: Record<string, string[]> = {};
  for (const [from, targets] of Object.entries(next.transitions ?? {})) {
    const source = normId(from);
    assertThat(
      known.has(source),
      `Transición desde un estado que no existe: ${from}`,
    );
    const to = [...new Set(targets.map(normId))];
    for (const target of to) {
      assertThat(
        known.has(target),
        `Transición hacia un estado que no existe: ${target}`,
      );
      assertThat(
        target !== source,
        `Un estado no puede pasar a sí mismo (${source})`,
      );
    }
    if (to.length) transitions[source] = to;
  }

  return { statuses, transitions, issueTypes, areas };
}

function normId(id: string): string {
  const value = (id ?? '').trim().toUpperCase();
  assertThat(
    ID.test(value),
    `Id no válido «${id}»: mayúsculas, números y _, empezando por letra`,
  );
  return value;
}

function normName(name: string): string {
  const value = (name ?? '').trim();
  assertThat(
    value.length > 0 && value.length <= 40,
    'Los nombres llevan 1-40 caracteres',
  );
  return value;
}