// Cases (docs/console.md): one queue for everything someone has to decide. Reports, rating reviews, removal
// requests, catalogs' deletion requests and appeals. The routes in app.ts check who may open one and carry out a
// decision's effects; this keeps the cases, their threads, and who may see and decide them.
import { and, count, desc, eq, gt, inArray, lt, or, sql, schema, type AuditTags, type Database } from "@t5de/db";
import { ProductError } from "./products";
import { Permissions, type Permission, type Who } from "./permissions";

const { caseNote, catalog, hosting, moderationCase, product, user } = schema;

export const caseKinds = ["report", "rating-review", "removal-request", "catalog-deletion", "appeal"] as const;
export type CaseKind = (typeof caseKinds)[number];
export type Case = typeof moderationCase.$inferSelect;

/** The permission that decides each kind of case (moderators hold them hub-wide). */
const decidedWith: Record<CaseKind, Permission> = {
  report: "case:resolve",
  "rating-review": "product:rate-lower",
  "removal-request": "product:remove",
  "catalog-deletion": "catalog:delete-review",
  appeal: "case:resolve",
};

/** The actions people can appeal, and whom they affect: a product's creator, a catalog's owner, or the person. */
export const appealable: Record<string, "creator" | "owner" | "person"> = {
  "product.remove": "creator",
  "product.edit": "creator",
  "product.lock": "creator",
  "product.revert": "creator",
  "catalog.delist": "creator",
  "catalog.suspend": "owner",
  "catalog.reject": "owner",
  "catalog.member_ban": "person",
  "catalog.member_decline": "person",
};

/** Reports a person may open in an hour. */
export const reportsPerHour = 10;

export class Cases {
  constructor(
    private readonly db: Database,
    private readonly perms: Permissions,
  ) {}

  async get(id: number): Promise<Case> {
    const [c] = await this.db.select().from(moderationCase).where(eq(moderationCase.id, id));
    if (!c) throw new ProductError(404, "not_found", "No such case.");
    return c;
  }

  /** The open case of a kind about a resource (one each), if any; with `openedBy`, only theirs. */
  async findOpen(kind: CaseKind, tags: AuditTags, openedBy?: string): Promise<Case | undefined> {
    const conds = [eq(moderationCase.kind, kind), eq(moderationCase.status, "open")];
    for (const [k, v] of Object.entries(tags)) if (v) conds.push(sql`${moderationCase.tags}->>${k} = ${v}`);
    if (openedBy) conds.push(eq(moderationCase.openedBy, openedBy));
    const [c] = await this.db.select().from(moderationCase).where(and(...conds)).limit(1);
    return c;
  }

  async open(kind: CaseKind, openedBy: string, tags: AuditTags, reason: string, data: Record<string, unknown> = {}) {
    const [c] = await this.db
      .insert(moderationCase)
      .values({ kind, openedBy, tags, reason: reason.trim().slice(0, 2000), data })
      .returning();
    return c!;
  }

  /** A report: at most reportsPerHour an hour, and one open report per person and resource. */
  async report(openedBy: string, tags: AuditTags, reason: string) {
    if (!reason.trim()) throw new ProductError(400, "reason_needed", "Say what's wrong.");
    const since = new Date(Date.now() - 60 * 60 * 1000);
    const [recent] = await this.db
      .select({ n: count() })
      .from(moderationCase)
      .where(and(eq(moderationCase.kind, "report"), eq(moderationCase.openedBy, openedBy), gt(moderationCase.createdAt, since)));
    if ((recent?.n ?? 0) >= reportsPerHour)
      throw new ProductError(429, "rate_limited", "That's a lot of reports. Try again in an hour.");
    if (await this.findOpen("report", tags, openedBy))
      throw new ProductError(409, "already_reported", "You reported that already; moderators will look at it.");
    return this.open("report", openedBy, tags, reason);
  }

  /** The catalogs hosting a product (whose teams decide reports about it). */
  private async hostsOf(productId: string): Promise<string[]> {
    const rows = await this.db.selectDistinct({ id: hosting.catalogId }).from(hosting).where(eq(hosting.productId, productId));
    return rows.map((r) => r.id);
  }

  /**
   * Whether someone may decide a case: moderators by the kind's permission (an appeal by a different moderator than
   * the one who acted, unless an admin, flagged in the audit log); reports about a product also its hosting catalogs'
   * teams (case:resolve there).
   */
  async canDecide(who: Who, c: Case): Promise<boolean> {
    const perm = decidedWith[c.kind as CaseKind];
    if (!perm) return false;
    if (this.perms.hub(who).has(perm)) return !(c.kind === "appeal" && c.data.actorId === who.id && who.role !== "admin");
    if (c.kind === "report" && c.tags.product)
      for (const id of await this.hostsOf(c.tags.product))
        if (await this.perms.can(who, "case:resolve", { type: "catalog", id })) return true;
    return false;
  }

  /** Whether someone may see a case: its opener, its assignee, those deciding it, and (but for reports, which keep
   * who reported private) those with case:read at what it's about. */
  async canSee(who: Who, c: Case): Promise<boolean> {
    if (c.openedBy === who.id || c.assignee === who.id) return true;
    if (this.perms.hub(who).has("case:read") || (await this.canDecide(who, c))) return true;
    if (c.kind === "report") return false;
    if (c.tags.catalog && (await this.perms.can(who, "case:read", { type: "catalog", id: c.tags.catalog }))) return true;
    if (c.tags.product && (await this.perms.can(who, "case:read", { type: "product", id: c.tags.product }))) return true;
    return false;
  }

  /** The cases a person may see (as canSee), newest first. */
  async list(who: Who, f: { status?: string; kind?: string; mine?: boolean; before?: number; limit?: number }) {
    const conds = [];
    if (f.mine) conds.push(eq(moderationCase.openedBy, who.id));
    else if (!this.perms.hub(who).has("case:read")) {
      const teams = await this.perms.teamCatalogs(who.id);
      const own = await this.perms.ownProducts(who.id);
      const visible = [eq(moderationCase.openedBy, who.id), eq(moderationCase.assignee, who.id)];
      if (teams.length) {
        visible.push(and(sql`${moderationCase.kind} <> 'report'`, inArray(sql`${moderationCase.tags}->>'catalog'`, teams))!);
        visible.push(
          and(
            eq(moderationCase.kind, "report"),
            sql`exists (select 1 from ${hosting} h where h.product_id = ${moderationCase.tags}->>'product' and h.catalog_id in ${teams})`,
          )!,
        );
      }
      if (own.length)
        visible.push(and(sql`${moderationCase.kind} <> 'report'`, inArray(sql`${moderationCase.tags}->>'product'`, own))!);
      conds.push(or(...visible)!);
    }
    if (f.status) conds.push(eq(moderationCase.status, f.status));
    if (f.kind) conds.push(eq(moderationCase.kind, f.kind));
    if (f.before) conds.push(lt(moderationCase.id, f.before));
    return this.db
      .select()
      .from(moderationCase)
      .where(conds.length ? and(...conds) : undefined)
      .orderBy(desc(moderationCase.id))
      .limit(Math.max(1, Math.min(f.limit ?? 50, 200)));
  }

  /** People's usernames and resources' names for cases (to show and link them). */
  async names(cases: Case[]) {
    const people = new Set<string>();
    const products = new Set<string>();
    const catalogs = new Set<string>();
    for (const c of cases) {
      for (const p of [c.openedBy, c.assignee, c.decidedBy, c.tags.person]) if (p) people.add(p);
      if (c.tags.product) products.add(c.tags.product);
      if (c.tags.catalog) catalogs.add(c.tags.catalog);
    }
    const [ps, prs, cs] = await Promise.all([
      people.size
        ? this.db.select({ id: user.id, name: user.displayUsername, username: user.username }).from(user).where(inArray(user.id, [...people]))
        : [],
      products.size ? this.db.select({ id: product.id, name: product.name }).from(product).where(inArray(product.id, [...products])) : [],
      catalogs.size ? this.db.select({ id: catalog.id, name: catalog.name }).from(catalog).where(inArray(catalog.id, [...catalogs])) : [],
    ]);
    const names: Record<string, string> = {};
    for (const p of ps) names[p.id] = p.name ?? p.username ?? "";
    for (const x of [...prs, ...cs]) names[x.id] = x.name;
    return names;
  }

  async decide(c: Case, by: string, status: "resolved" | "declined", resolution: string) {
    if (c.status !== "open") throw new ProductError(409, "decided", "That case is decided already.");
    const [updated] = await this.db
      .update(moderationCase)
      .set({ status, resolution: resolution.trim().slice(0, 2000), decidedBy: by, decidedAt: new Date() })
      .where(and(eq(moderationCase.id, c.id), eq(moderationCase.status, "open")))
      .returning();
    if (!updated) throw new ProductError(409, "decided", "That case is decided already.");
    return updated;
  }

  async assign(c: Case, assignee: string | null) {
    const [updated] = await this.db.update(moderationCase).set({ assignee }).where(eq(moderationCase.id, c.id)).returning();
    return updated!;
  }

  async notes(c: Case, internalToo: boolean) {
    return this.db
      .select({
        id: caseNote.id,
        by: user.displayUsername,
        byId: caseNote.byId,
        body: caseNote.body,
        internal: caseNote.internal,
        at: caseNote.createdAt,
      })
      .from(caseNote)
      .leftJoin(user, eq(user.id, caseNote.byId))
      .where(and(eq(caseNote.caseId, c.id), internalToo ? undefined : eq(caseNote.internal, false)))
      .orderBy(caseNote.id);
  }

  async addNote(c: Case, byId: string, body: string, internal: boolean) {
    body = body.trim().slice(0, 4000);
    if (!body) throw new ProductError(400, "invalid", "Write something.");
    await this.db.insert(caseNote).values({ caseId: c.id, byId, body, internal });
    await this.db.update(moderationCase).set({ updatedAt: new Date() }).where(eq(moderationCase.id, c.id));
  }

  /** Open cases a person could decide (for the console's to-dos): every one for moderators, else reports about
   * products their catalogs host. */
  async openToDecide(who: Who): Promise<number> {
    const open = eq(moderationCase.status, "open");
    if (this.perms.hub(who).has("case:resolve")) {
      const [row] = await this.db.select({ n: count() }).from(moderationCase).where(open);
      return row?.n ?? 0;
    }
    const teams = await this.perms.teamCatalogs(who.id);
    if (!teams.length) return 0;
    const [row] = await this.db
      .select({ n: count() })
      .from(moderationCase)
      .where(
        and(
          open,
          eq(moderationCase.kind, "report"),
          sql`exists (select 1 from ${hosting} h where h.product_id = ${moderationCase.tags}->>'product' and h.catalog_id in ${teams})`,
        ),
      );
    return row?.n ?? 0;
  }
}