import { randomBytes } from "node:crypto";

import { TRPCError } from "@trpc/server";
import {
  and,
  desc,
  eq,
  gt,
  inArray,
  isNotNull,
  isNull,
  ne,
  sql,
} from "drizzle-orm";
import { z } from "zod";

import { router, protectedProcedure, workspaceProcedure } from "@/server/trpc";
import { userOwnsEmail } from "@/server/lib/identity";
import {
  userEmailIdentities,
  workspaceInvites,
  workspaceMembers,
  workspaces,
  users,
} from "@tasks/database/schema";
import {
  mergeInviteSuggestions,
  type InviteSuggestion,
  type InviteSuggestionKnownUser,
  type InviteSuggestionMember,
  type InviteSuggestionNewEmail,
  type InviteSuggestionPendingInvite,
} from "@tasks/shared";

/**
 * Workspace invites. Owners and admins create invites for an email address;
 * the recipient redeems the opaque `token` at /invite/[token].
 *
 * Security model:
 *   - `create`, `list`, `revoke` are workspace-scoped and require the caller
 *     to be `owner` or `admin` on the target workspace.
 *   - `accept` is a *public* procedure (no workspace handle) — the token
 *     itself is the capability. It does require an authenticated session
 *     so we can write the `workspace_members.user_id` row, and it calls
 *     `userOwnsEmail()` from Task 1 to make sure the human accepting the
 *     invite actually controls the invited address under any of their
 *     linked identities. Mismatch returns a structured error so the UI can
 *     show the explainer instead of silently 403-ing.
 *
 * Email delivery is not in this task — `create` returns the accept URL so
 * an operator can copy/paste it. The Resend/Postmark integration is a
 * follow-up.
 */

const ROLE_VALUES = ["owner", "admin", "member"] as const;
const inviteRoleSchema = z.enum(ROLE_VALUES);
const inviteEmailSchema = z
  .string()
  .trim()
  .toLowerCase()
  .pipe(z.string().email({ message: "Please enter a valid email address" }));

function assertCanManageInvites(role: string): void {
  if (role !== "owner" && role !== "admin") {
    throw new TRPCError({
      code: "FORBIDDEN",
      message: "Only owners and admins can manage invites",
    });
  }
}

function generateInviteToken(): string {
  // 32 random bytes -> 43-char base64url. Enough entropy that a token guess
  // is astronomically improbable; short enough to fit in a copy-paste URL.
  return randomBytes(32).toString("base64url");
}

/**
 * Escape the three ILIKE metacharacters (`%`, `_`, `\`) so a user-typed
 * query can be safely interpolated into an `ILIKE '...pattern...' ESCAPE
 * '\\'` clause without letting "100%" or "snake_case" match more than the
 * literal characters typed.
 */
function escapeIlike(value: string): string {
  return value.replace(/\\/g, "\\\\").replace(/%/g, "\\%").replace(/_/g, "\\_");
}

function buildAcceptUrl(token: string): string {
  // `NEXT_PUBLIC_APP_URL` is the canonical origin for invite links. Falls
  // back to a path-only URL so the procedure still works in environments
  // without it set (the UI can prefix `window.location.origin` if needed).
  const base = process.env.NEXT_PUBLIC_APP_URL?.replace(/\/$/, "");
  return base ? `${base}/invite/${token}` : `/invite/${token}`;
}

export const invitesRouter = router({
  /**
   * Create or return-existing an open invite for `email` to the given
   * workspace. Idempotent on the (workspace_id, lower(email)) pair: if an
   * open invite already exists for that address, we return it instead of
   * inserting a duplicate (the partial unique constraint would block it
   * anyway).
   */
  create: workspaceProcedure
    .input(
      z.object({
        email: inviteEmailSchema,
        role: inviteRoleSchema,
      }),
    )
    .mutation(async ({ ctx, input }) => {
      assertCanManageInvites(ctx.workspace.role);

      const inviterId = ctx.session.user.id;

      // Don't let inviters invite themselves — confusing failure mode.
      const [inviter] = await ctx.db
        .select({ email: users.email })
        .from(users)
        .where(eq(users.id, inviterId))
        .limit(1);
      if (inviter?.email.toLowerCase() === input.email) {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "You can't invite yourself.",
        });
      }

      // Already a member? Surface a clear error so the inviter knows.
      const [existingMember] = await ctx.db
        .select({ userId: workspaceMembers.userId })
        .from(workspaceMembers)
        .innerJoin(users, eq(users.id, workspaceMembers.userId))
        .where(
          and(
            eq(workspaceMembers.workspaceId, ctx.workspace.id),
            eq(users.email, input.email),
          ),
        )
        .limit(1);
      if (existingMember) {
        throw new TRPCError({
          code: "CONFLICT",
          message: "This person is already a member of this workspace.",
        });
      }

      // Reuse an open invite if one already exists for this (workspace, email).
      const [existingInvite] = await ctx.db
        .select()
        .from(workspaceInvites)
        .where(
          and(
            eq(workspaceInvites.workspaceId, ctx.workspace.id),
            eq(workspaceInvites.email, input.email),
            isNull(workspaceInvites.acceptedAt),
            isNull(workspaceInvites.revokedAt),
          ),
        )
        .limit(1);
      if (existingInvite) {
        return {
          invite: existingInvite,
          acceptUrl: buildAcceptUrl(existingInvite.token),
          reused: true as const,
        };
      }

      const token = generateInviteToken();
      const [invite] = await ctx.db
        .insert(workspaceInvites)
        .values({
          workspaceId: ctx.workspace.id,
          email: input.email,
          role: input.role,
          invitedByUserId: inviterId,
          token,
        })
        .returning();

      return {
        invite: invite!,
        acceptUrl: buildAcceptUrl(invite!.token),
        reused: false as const,
      };
    }),

  /** Pending (non-accepted, non-revoked) invites for the workspace. */
  list: workspaceProcedure.query(async ({ ctx }) => {
    assertCanManageInvites(ctx.workspace.role);

    return ctx.db
      .select({
        id: workspaceInvites.id,
        email: workspaceInvites.email,
        role: workspaceInvites.role,
        token: workspaceInvites.token,
        expiresAt: workspaceInvites.expiresAt,
        createdAt: workspaceInvites.createdAt,
        invitedByUserId: workspaceInvites.invitedByUserId,
        invitedByName: users.name,
        invitedByEmail: users.email,
      })
      .from(workspaceInvites)
      .innerJoin(users, eq(users.id, workspaceInvites.invitedByUserId))
      .where(
        and(
          eq(workspaceInvites.workspaceId, ctx.workspace.id),
          isNull(workspaceInvites.acceptedAt),
          isNull(workspaceInvites.revokedAt),
        ),
      )
      .orderBy(desc(workspaceInvites.createdAt));
  }),

  /** Revoke an open invite. Caller must be owner/admin on the invite's workspace. */
  revoke: protectedProcedure
    .input(z.object({ inviteId: z.string().uuid() }))
    .mutation(async ({ ctx, input }) => {
      const [invite] = await ctx.db
        .select({
          id: workspaceInvites.id,
          workspaceId: workspaceInvites.workspaceId,
          acceptedAt: workspaceInvites.acceptedAt,
          revokedAt: workspaceInvites.revokedAt,
        })
        .from(workspaceInvites)
        .where(eq(workspaceInvites.id, input.inviteId))
        .limit(1);
      if (!invite) {
        throw new TRPCError({ code: "NOT_FOUND", message: "Invite not found" });
      }
      if (invite.acceptedAt || invite.revokedAt) {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "This invite has already been closed.",
        });
      }

      // Authorize against the invite's workspace, not via workspaceProcedure
      // (we don't take a workspace handle in this input; the invite tells us).
      const callerId = ctx.session.user.id;
      const [membership] = await ctx.db
        .select({ role: workspaceMembers.role })
        .from(workspaceMembers)
        .where(
          and(
            eq(workspaceMembers.workspaceId, invite.workspaceId),
            eq(workspaceMembers.userId, callerId),
          ),
        )
        .limit(1);
      if (!membership) {
        throw new TRPCError({ code: "FORBIDDEN" });
      }
      assertCanManageInvites(membership.role);

      await ctx.db
        .update(workspaceInvites)
        .set({ revokedAt: new Date() })
        .where(eq(workspaceInvites.id, invite.id));

      return { ok: true as const };
    }),

  /**
   * Public-by-token redemption. Caller must be authenticated AND own (under
   * any linked identity) the email the invite was sent to. On mismatch we
   * throw a `FORBIDDEN` with a structured `cause` the UI can render as the
   * "link this email first" explainer.
   */
  accept: protectedProcedure
    .input(z.object({ token: z.string().min(8).max(128) }))
    .mutation(async ({ ctx, input }) => {
      const now = new Date();

      const [invite] = await ctx.db
        .select({
          id: workspaceInvites.id,
          workspaceId: workspaceInvites.workspaceId,
          email: workspaceInvites.email,
          role: workspaceInvites.role,
          acceptedAt: workspaceInvites.acceptedAt,
          revokedAt: workspaceInvites.revokedAt,
          expiresAt: workspaceInvites.expiresAt,
        })
        .from(workspaceInvites)
        .where(eq(workspaceInvites.token, input.token))
        .limit(1);

      if (!invite) {
        throw new TRPCError({
          code: "NOT_FOUND",
          message: "This invite link is not valid.",
        });
      }
      if (invite.revokedAt) {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "This invite has been revoked.",
        });
      }
      if (invite.acceptedAt) {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "This invite has already been accepted.",
        });
      }
      if (invite.expiresAt.getTime() < now.getTime()) {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "This invite has expired.",
        });
      }

      const callerId = ctx.session.user.id;

      // Identity check: under Task 1's semantics, the caller must have a
      // verified identity row matching the invited email. We surface the
      // mismatch with a structured cause so the redeem page can render the
      // "link this email to your account first" explainer.
      const owns = await userOwnsEmail(callerId, invite.email);
      if (!owns) {
        throw new TRPCError({
          code: "FORBIDDEN",
          message: `This invite was sent to ${invite.email}. Link that email to your account from your profile, then come back to this link.`,
          cause: { reason: "email_not_owned", invitedEmail: invite.email },
        });
      }

      // Already a member? Don't fail — just close the invite. Common when
      // someone accepts a re-invite after already being added by another flow.
      const [existingMembership] = await ctx.db
        .select({ id: workspaceMembers.id })
        .from(workspaceMembers)
        .where(
          and(
            eq(workspaceMembers.workspaceId, invite.workspaceId),
            eq(workspaceMembers.userId, callerId),
          ),
        )
        .limit(1);
      if (!existingMembership) {
        await ctx.db.insert(workspaceMembers).values({
          workspaceId: invite.workspaceId,
          userId: callerId,
          role: invite.role,
        });
      }

      await ctx.db
        .update(workspaceInvites)
        .set({ acceptedAt: now })
        .where(eq(workspaceInvites.id, invite.id));

      const [workspace] = await ctx.db
        .select({ id: workspaces.id, slug: workspaces.slug, name: workspaces.name })
        .from(workspaces)
        .where(eq(workspaces.id, invite.workspaceId))
        .limit(1);

      return {
        workspace: workspace!,
        role: invite.role,
      };
    }),

  /**
   * Typeahead for the invite dialog's "Who do you want to invite?" field.
   * Returns up to 10 suggestions across four kinds (see `InviteSuggestion`
   * in `@tasks/shared`) so the UI can disambiguate between an existing
   * member, an outstanding pending invite, a user from one of the
   * inviter's other workspaces, and a brand-new email.
   *
   * Security model:
   *   - Workspace-scoped (`workspaceProcedure`) and owner/admin only —
   *     non-managers should not be probing this surface to enumerate
   *     teammates.
   *   - The `known_user` kind is fenced to workspaces the **inviter** also
   *     belongs to. A global user search would leak the existence of
   *     accounts across tenants; this restriction is the security contract
   *     called out in the task spec (acceptance criterion: "Tenancy fence
   *     holds").
   *   - All ILIKE patterns are escaped via `escapeIlike` so a query like
   *     "100%" can't broaden the match.
   *
   * Empty / single-char queries return `[]` — the UI uses this as a "show
   * nothing yet" sentinel and avoids hammering the DB on every keystroke.
   */
  suggestRecipient: workspaceProcedure
    .input(z.object({ query: z.string() }))
    .query(async ({ ctx, input }): Promise<InviteSuggestion[]> => {
      assertCanManageInvites(ctx.workspace.role);

      const raw = input.query.trim();
      if (raw.length < 2) return [];

      const qLower = raw.toLowerCase();
      const escaped = escapeIlike(qLower);
      const prefixPattern = `${escaped}%`;
      const substringPattern = `%${escaped}%`;

      const inviterId = ctx.session.user.id;
      const totalLimit = 10;

      const memberMatchSql = sql`(
        ${users.name} ILIKE ${substringPattern} ESCAPE '\\'
        OR ${users.email} ILIKE ${prefixPattern} ESCAPE '\\'
        OR ${userEmailIdentities.email} ILIKE ${prefixPattern} ESCAPE '\\'
      )`;

      const memberRows = await ctx.db
        .selectDistinct({
          userId: users.id,
          name: users.name,
          email: users.email,
          role: workspaceMembers.role,
        })
        .from(workspaceMembers)
        .innerJoin(users, eq(users.id, workspaceMembers.userId))
        .leftJoin(
          userEmailIdentities,
          and(
            eq(userEmailIdentities.userId, users.id),
            isNotNull(userEmailIdentities.verifiedAt),
          ),
        )
        .where(
          and(eq(workspaceMembers.workspaceId, ctx.workspace.id), memberMatchSql),
        )
        .limit(totalLimit);

      const members: InviteSuggestionMember[] = memberRows.map((r) => ({
        kind: "member",
        userId: r.userId,
        name: r.name,
        email: r.email,
        role: r.role,
      }));

      // `workspace_invites.email` is stored lowercased on insert
      // (see `invites.create`), so a prefix ILIKE against the column is
      // already case-insensitive without an extra `lower()` wrap.
      const inviteRows = await ctx.db
        .select({
          inviteId: workspaceInvites.id,
          email: workspaceInvites.email,
          role: workspaceInvites.role,
          expiresAt: workspaceInvites.expiresAt,
        })
        .from(workspaceInvites)
        .where(
          and(
            eq(workspaceInvites.workspaceId, ctx.workspace.id),
            isNull(workspaceInvites.acceptedAt),
            isNull(workspaceInvites.revokedAt),
            gt(workspaceInvites.expiresAt, new Date()),
            sql`${workspaceInvites.email} ILIKE ${prefixPattern} ESCAPE '\\'`,
          ),
        )
        .limit(totalLimit);

      const pendingInvites: InviteSuggestionPendingInvite[] = inviteRows.map(
        (r) => ({
          kind: "pending_invite",
          inviteId: r.inviteId,
          email: r.email,
          role: r.role,
          expiresAt: r.expiresAt,
        }),
      );

      // Tenancy fence: the candidate pool for `known_user` is restricted to
      // users who share at least one workspace with the inviter. We resolve
      // that pool here as a concrete UUID array so the candidate query is a
      // plain `IN (...)` against the same `workspace_members` table, which
      // is easy to reason about and safe even if Drizzle's correlated
      // subquery alias rules change. If the inviter happens to share zero
      // workspaces with anyone (e.g. they only own a brand-new solo
      // workspace), we skip the candidate query entirely.
      const inviterWorkspaceRows = await ctx.db
        .selectDistinct({ workspaceId: workspaceMembers.workspaceId })
        .from(workspaceMembers)
        .where(eq(workspaceMembers.userId, inviterId));
      const inviterWorkspaceIds = inviterWorkspaceRows.map((r) => r.workspaceId);

      let knownUsers: InviteSuggestionKnownUser[] = [];
      if (inviterWorkspaceIds.length > 0) {
        const knownCandidates = await ctx.db
          .selectDistinct({
            userId: users.id,
            name: users.name,
            email: users.email,
          })
          .from(users)
          .innerJoin(workspaceMembers, eq(workspaceMembers.userId, users.id))
          .leftJoin(
            userEmailIdentities,
            and(
              eq(userEmailIdentities.userId, users.id),
              isNotNull(userEmailIdentities.verifiedAt),
            ),
          )
          .where(
            and(
              inArray(workspaceMembers.workspaceId, inviterWorkspaceIds),
              ne(users.id, inviterId),
              memberMatchSql,
            ),
          )
          .limit(totalLimit * 2);

        if (knownCandidates.length > 0) {
          const candidateIds = knownCandidates.map((c) => c.userId);
          const sharedCountRows = await ctx.db
            .select({
              userId: workspaceMembers.userId,
              count: sql<number>`count(distinct ${workspaceMembers.workspaceId})::int`.as(
                "count",
              ),
            })
            .from(workspaceMembers)
            .where(
              and(
                inArray(workspaceMembers.userId, candidateIds),
                inArray(workspaceMembers.workspaceId, inviterWorkspaceIds),
              ),
            )
            .groupBy(workspaceMembers.userId);

          const countMap = new Map(
            sharedCountRows.map((r) => [r.userId, Number(r.count)]),
          );

          knownUsers = knownCandidates.map((c) => ({
            kind: "known_user",
            userId: c.userId,
            name: c.name,
            email: c.email,
            sharedWorkspaceCount: countMap.get(c.userId) ?? 0,
          }));
        }
      }

      const emailParse = z.string().email().safeParse(qLower);
      const newEmail: InviteSuggestionNewEmail | null = emailParse.success
        ? { kind: "new_email", email: qLower, valid: true }
        : null;

      return mergeInviteSuggestions({
        members,
        pendingInvites,
        knownUsers,
        newEmail,
        limit: totalLimit,
      });
    }),
});

export type InvitesRouter = typeof invitesRouter;

// Re-exports used by callers that want to share the schema (e.g. the smart
// recipient autocomplete in Task 3).
export const inviteRoleValues = ROLE_VALUES;
export { inviteRoleSchema };