import type { Prisma } from "@prisma/client";
import { z } from "zod";
import { assertCan, ServiceError, type ServiceCtx } from "@/server/services/context";

/**
 * Read-only audit log viewer (spec §26). Requires `audit:read`; always tenant-bound via ctx.db
 * (the tenant client filters AuditLog by tenantId). Audit rows are never modified here.
 */

export const AUDIT_PAGE_SIZE = 50;

const dateStr = z
  .string()
  .regex(/^\d{4}-\d{2}-\d{2}$/)
  .optional()
  .catch(undefined);
const optStr = (max: number) =>
  z
    .string()
    .trim()
    .max(max)
    .transform((v) => v || undefined)
    .optional()
    .catch(undefined);

export const auditFilterSchema = z.object({
  from: dateStr,
  to: dateStr,
  actorId: optStr(64),
  action: optStr(40),
  entity: optStr(60),
  entityId: optStr(128),
  page: z.coerce.number().int().min(1).max(100_000).catch(1),
});
export type AuditFilter = z.infer<typeof auditFilterSchema>;

export function auditWhere(f: AuditFilter): Prisma.AuditLogWhereInput {
  const createdAt: Prisma.DateTimeFilter = {};
  if (f.from) createdAt.gte = new Date(`${f.from}T00:00:00.000Z`);
  if (f.to) createdAt.lt = new Date(new Date(`${f.to}T00:00:00.000Z`).getTime() + 86_400_000);
  return {
    ...(f.from || f.to ? { createdAt } : {}),
    ...(f.actorId ? { actorId: f.actorId } : {}),
    ...(f.action ? { action: f.action } : {}),
    ...(f.entity ? { entity: f.entity } : {}),
    ...(f.entityId ? { entityId: { contains: f.entityId } } : {}),
  };
}

export async function queryAuditLog(ctx: ServiceCtx, input: unknown) {
  assertCan(ctx, "audit:read");
  const filter = auditFilterSchema.parse(input ?? {});
  const where = auditWhere(filter);
  const [rows, total, actions, entities, users] = await Promise.all([
    ctx.db.auditLog.findMany({
      where,
      orderBy: { createdAt: "desc" },
      skip: (filter.page - 1) * AUDIT_PAGE_SIZE,
      take: AUDIT_PAGE_SIZE,
      select: { id: true, createdAt: true, actorId: true, action: true, entity: true, entityId: true, scope: true },
    }),
    ctx.db.auditLog.count({ where }),
    ctx.db.auditLog.findMany({ distinct: ["action"], select: { action: true }, orderBy: { action: "asc" } }),
    ctx.db.auditLog.findMany({ distinct: ["entity"], select: { entity: true }, orderBy: { entity: "asc" } }),
    ctx.db.user.findMany({ select: { id: true, name: true }, orderBy: { name: "asc" } }),
  ]);
  return {
    rows,
    total,
    page: filter.page,
    pages: Math.max(1, Math.ceil(total / AUDIT_PAGE_SIZE)),
    filter,
    facets: { actions: actions.map((a) => a.action), entities: entities.map((e) => e.entity) },
    actors: users,
  };
}

export type DiffRow = { key: string; before: string | null; after: string | null; changed: boolean };

function show(v: unknown): string | null {
  if (v === undefined) return null;
  if (v === null) return "null";
  return typeof v === "string" ? v : JSON.stringify(v);
}

/** Field-wise before/after comparison (top-level keys; nested values rendered as JSON). */
export function diffAudit(before: unknown, after: unknown): DiffRow[] {
  const b = before && typeof before === "object" && !Array.isArray(before) ? (before as Record<string, unknown>) : null;
  const a = after && typeof after === "object" && !Array.isArray(after) ? (after as Record<string, unknown>) : null;
  if (!b && !a) {
    if (before === undefined && after === undefined) return [];
    if (before == null && after == null) return [];
    return [{ key: "value", before: show(before ?? undefined), after: show(after ?? undefined), changed: show(before) !== show(after) }];
  }
  const keys = [...new Set([...Object.keys(b ?? {}), ...Object.keys(a ?? {})])].sort();
  return keys.map((key) => {
    const bv = show(b?.[key]);
    const av = show(a?.[key]);
    return { key, before: bv, after: av, changed: bv !== av };
  });
}

export async function getAuditEntry(ctx: ServiceCtx, id: unknown) {
  assertCan(ctx, "audit:read");
  const entryId = z.string().min(1).max(64).parse(id);
  const row = await ctx.db.auditLog.findFirst({ where: { id: entryId } });
  if (!row) throw new ServiceError("not_found", "audit entry not found");
  const actor = row.actorId ? await ctx.db.user.findFirst({ where: { id: row.actorId }, select: { name: true } }) : null;
  return {
    ...row,
    actorName: actor?.name ?? null,
    diff: diffAudit(row.before ?? undefined, row.after ?? undefined),
    // captured by writeAuditLog from the request (spec §26); null for worker/script writes
    ip: row.ipAddress,
    userAgent: row.userAgent,
  };
}