import { eq } from "drizzle-orm";
import { Hono } from "hono";
import type { Db } from "../db/client.js";
import {
  activityLog,
  approvalPolicies,
  approvalSteps,
  invoiceComments,
  invoices,
} from "../db/schema/index.js";
import type { AppBindings } from "../auth/middleware.js";
import { errorJson } from "../http.js";
import {
  asMoney,
  asString,
  caller,
  firstById,
  iso,
  isUuid,
  parseJsonBody,
  requireCan,
  rowsOf,
} from "./helpers.js";
import { appendActivity, remainingPending } from "../approvals.js";
import type { UserRole } from "../env.js";

type PolicyRow = typeof approvalPolicies.$inferSelect;
type StepRow = typeof approvalSteps.$inferSelect;
type InvoiceRow = typeof invoices.$inferSelect;
type CommentRow = typeof invoiceComments.$inferSelect;
type ActivityRow = typeof activityLog.$inferSelect;

const DECISIONS = ["approve", "reject", "skip"] as const;
type Decision = (typeof DECISIONS)[number];

function isDecision(value: string): value is Decision {
  return (DECISIONS as readonly string[]).includes(value);
}

function toPolicy(row: PolicyRow) {
  return {
    id: row.id,
    name: row.name,
    priority: row.priority,
    amountThreshold: row.amountThreshold,
    skipBelowAmount: row.skipBelowAmount,
    active: row.active,
    createdAt: iso(row.createdAt),
    updatedAt: iso(row.updatedAt),
  };
}

function toStep(row: StepRow) {
  return {
    id: row.id,
    invoiceId: row.invoiceId,
    policyId: row.policyId,
    stepOrder: row.stepOrder,
    approverRole: row.approverRole,
    assigneeUserId: row.assigneeUserId,
    status: row.status,
    actedByUserId: row.actedByUserId,
    actedAt: row.actedAt ? iso(row.actedAt) : null,
    createdAt: iso(row.createdAt),
  };
}

function inboxVisible(step: StepRow, user: { id: string; role: UserRole }): boolean {
  if (step.status !== "pending") return false;
  if (step.assigneeUserId) return step.assigneeUserId === user.id;
  return user.role === "admin" || user.role === step.approverRole;
}

export function createApprovalRoutes(handle: Db) {
  const routes = new Hono<AppBindings>();

  routes.get("/approval-policies", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const rows = await rowsOf<PolicyRow>(handle, approvalPolicies);
    return c.json({ items: rows.map(toPolicy) });
  });

  routes.post("/approval-policies", async (c) => {
    const denied = requireCan(c, "admin:settings");
    if (denied) return denied;
    const body = await parseJsonBody(c);
    const name = asString(body.name).trim();
    if (!name) return errorJson(c, 400, "VALIDATION_ERROR", "Name is required.");
    const [row] = await handle.db
      .insert(approvalPolicies)
      .values({
        name,
        priority: typeof body.priority === "number" ? body.priority : 100,
        amountThreshold: asMoney(body.amountThreshold),
        skipBelowAmount: asMoney(body.skipBelowAmount),
        active: body.active === false ? false : true,
      })
      .returning();
    return c.json(toPolicy(row), 201);
  });

  routes.get("/approval-policies/:id", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid policy id.");
    const row = await firstById<PolicyRow>(handle, approvalPolicies, id);
    if (!row) return errorJson(c, 404, "NOT_FOUND", "Policy not found.");
    return c.json(toPolicy(row));
  });

  routes.patch("/approval-policies/:id", async (c) => {
    const denied = requireCan(c, "admin:settings");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid policy id.");
    const existing = await firstById<PolicyRow>(handle, approvalPolicies, id);
    if (!existing) return errorJson(c, 404, "NOT_FOUND", "Policy not found.");
    const body = await parseJsonBody(c);
    const patch: Partial<typeof approvalPolicies.$inferInsert> & { id: string } = {
      id,
      updatedAt: new Date(),
    };
    if (body.name !== undefined) {
      const name = asString(body.name).trim();
      if (!name) return errorJson(c, 400, "VALIDATION_ERROR", "Name is required.");
      patch.name = name;
    }
    if (typeof body.priority === "number") patch.priority = body.priority;
    if (body.amountThreshold !== undefined) patch.amountThreshold = asMoney(body.amountThreshold);
    if (body.skipBelowAmount !== undefined) patch.skipBelowAmount = asMoney(body.skipBelowAmount);
    if (typeof body.active === "boolean") patch.active = body.active;
    const [row] = await handle.db
      .update(approvalPolicies)
      .set(patch)
      .where(eq(approvalPolicies.id, id))
      .returning();
    return c.json(toPolicy(row));
  });

  routes.get("/inbox", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const user = caller(c);
    const steps = await rowsOf<StepRow>(handle, approvalSteps);
    const invoiceRows = await rowsOf<InvoiceRow>(handle, invoices);
    const items = steps
      .filter((step) => inboxVisible(step, user))
      .map((step) => {
        const invoice = invoiceRows.find((row) => row.id === step.invoiceId);
        return {
          ...toStep(step),
          invoiceNumber: invoice?.invoiceNumber ?? null,
          amount: invoice?.amount ?? null,
          vendorId: invoice?.vendorId ?? null,
        };
      });
    return c.json({ items });
  });

  routes.post("/approval-steps/:id/decisions", async (c) => {
    const denied = requireCan(c, "approve:invoices");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid step id.");
    const step = await firstById<StepRow>(handle, approvalSteps, id);
    if (!step) return errorJson(c, 404, "NOT_FOUND", "Approval step not found.");
    if (step.status !== "pending") {
      return errorJson(c, 409, "CONFLICT", "Step is not pending.");
    }
    const body = await parseJsonBody(c);
    const action = asString(body.action);
    if (!isDecision(action)) {
      return errorJson(c, 400, "VALIDATION_ERROR", "action must be approve, reject, or skip.");
    }
    const user = caller(c);
    const nextStatus =
      action === "approve" ? "approved" : action === "reject" ? "rejected" : "skipped";
    const [updated] = await handle.db
      .update(approvalSteps)
      .set({
        id,
        status: nextStatus,
        actedByUserId: user.id,
        actedAt: new Date(),
      })
      .where(eq(approvalSteps.id, id))
      .returning();
    await appendActivity(
      handle,
      step.invoiceId,
      user.id,
      action === "approve"
        ? "Step approved."
        : action === "reject"
          ? "Step rejected."
          : "Step skipped.",
    );
    let invoiceStatus: InvoiceRow["status"] | undefined;
    if (action === "reject") invoiceStatus = "rejected";
    else if ((await remainingPending(handle, step.invoiceId)).length === 0) {
      invoiceStatus = "approved";
    }
    if (invoiceStatus) {
      await handle.db
        .update(invoices)
        .set({ id: step.invoiceId, status: invoiceStatus, updatedAt: new Date() })
        .where(eq(invoices.id, step.invoiceId))
        .returning();
    }
    return c.json(toStep(updated));
  });

  routes.get("/invoices/:id/comments", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid invoice id.");
    const invoice = await firstById<InvoiceRow>(handle, invoices, id);
    if (!invoice) return errorJson(c, 404, "NOT_FOUND", "Invoice not found.");
    const rows = (await rowsOf<CommentRow>(handle, invoiceComments)).filter(
      (row) => row.invoiceId === id,
    );
    return c.json({
      items: rows.map((row) => ({
        id: row.id,
        invoiceId: row.invoiceId,
        authorUserId: row.authorUserId,
        body: row.body,
        createdAt: iso(row.createdAt),
      })),
    });
  });

  routes.post("/invoices/:id/comments", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid invoice id.");
    const invoice = await firstById<InvoiceRow>(handle, invoices, id);
    if (!invoice) return errorJson(c, 404, "NOT_FOUND", "Invoice not found.");
    const body = asString((await parseJsonBody(c)).body).trim();
    if (!body) return errorJson(c, 400, "VALIDATION_ERROR", "body is required.");
    const user = caller(c);
    const [row] = await handle.db
      .insert(invoiceComments)
      .values({ invoiceId: id, authorUserId: user.id, body })
      .returning();
    await appendActivity(handle, id, user.id, "Comment added.");
    return c.json(
      {
        id: row.id,
        invoiceId: row.invoiceId,
        authorUserId: row.authorUserId,
        body: row.body,
        createdAt: iso(row.createdAt),
      },
      201,
    );
  });

  routes.get("/invoices/:id/activity-logs", async (c) => {
    const denied = requireCan(c, "read:invoices");
    if (denied) return denied;
    const id = c.req.param("id");
    if (!isUuid(id)) return errorJson(c, 400, "VALIDATION_ERROR", "Invalid invoice id.");
    const invoice = await firstById<InvoiceRow>(handle, invoices, id);
    if (!invoice) return errorJson(c, 404, "NOT_FOUND", "Invoice not found.");
    const rows = (await rowsOf<ActivityRow>(handle, activityLog)).filter(
      (row) => row.invoiceId === id,
    );
    return c.json({
      items: rows.map((row) => ({
        id: row.id,
        invoiceId: row.invoiceId,
        actorUserId: row.actorUserId,
        message: row.message,
        createdAt: iso(row.createdAt),
      })),
    });
  });

  return routes;
}