import type { FastifyInstance } from "fastify";
import {
  and,
  eq,
  isNull,
  inArray,
  ledgerEvents,
  users,
  validationProgramUsers,
  validationPrograms,
  type Db,
} from "@parking/db";
import { VALIDATION_MODES, type ValidationMode } from "@parking/shared";
import { requirePermission } from "../auth.js";
import type { EventLog } from "../event-log.js";
import { liveValidations, sessionValidations } from "../validations.js";

// Merchant validations (bar / lavazh). The merchant is VALIDATION-ONLY: they scan the
// customer's ticket on their own device and apply their program — all money and paper
// stay at the booth, which settles net of these events. Program config is admin-composed
// on /setup/site (site:read/update — no dedicated permission); applying is the merchant
// user's `validation:create`, guarded FURTHER by the program↔user binding so a bar user
// can never apply the lavazh program. Every apply/void is a signed, attributed ledger
// event. See wiki/concepts/validation-discounts.md.
//   - GET  /api/validation/programs           : all programs + bound users. (site:read)
//   - PUT  /api/validation/programs/:id       : upsert config + bindings;   (site:update)
//                                               signs a config_change.
//   - GET  /api/validation/mine               : my bound ACTIVE programs.   (validation:create)
//   - GET  /api/validation/session/:identity  : minimal session view for    (validation:create)
//                                               the merchant screen (no money data).
//   - POST /api/validation/apply              : apply my program (signed).  (validation:create)
//   - POST /api/validation/void               : void my OWN unused apply.   (validation:create)

/** Well-formed program ids: kebab slugs ("bar", "lavazh", a future "hotel-2"). */
const ID_RE = /^[a-z][a-z0-9-]{1,31}$/;

interface ProgramBody {
  name?: string;
  mode?: ValidationMode;
  minutes?: number | null;
  percent?: number | null;
  maxAmountMinor?: number | null;
  maxPerDay?: number | null;
  active?: boolean;
  /** Full replacement set of bound user ids. */
  userIds?: string[];
}

interface ApplyBody {
  identity: string;
  programId: string;
  /** fixed mode only: the discount the merchant grants (minor units, ≤ maxAmountMinor). */
  amountMinor?: number;
}

interface VoidBody {
  eventId: string;
  identity: string;
}

/** null when valid, else the 400 message. Checks the per-mode parameter. */
function validateProgram(b: ProgramBody): string | null {
  if (!b.name || !String(b.name).trim()) return "name is required";
  if (!VALIDATION_MODES.includes(b.mode as ValidationMode)) return "mode must be comp|timeCredit|fixed|percent";
  const intOrNull = (v: unknown) => v == null || (Number.isInteger(v) && (v as number) > 0);
  if (!intOrNull(b.minutes)) return "minutes must be a positive integer";
  if (!intOrNull(b.maxAmountMinor)) return "maxAmountMinor must be a positive integer";
  if (!intOrNull(b.maxPerDay)) return "maxPerDay must be a positive integer";
  if (b.percent != null && (!Number.isInteger(b.percent) || b.percent < 1 || b.percent > 100))
    return "percent must be 1..100";
  if (b.mode === "timeCredit" && b.minutes == null) return "timeCredit needs minutes";
  if (b.mode === "percent" && b.percent == null) return "percent mode needs percent";
  if (b.mode === "fixed" && b.maxAmountMinor == null) return "fixed mode needs maxAmountMinor";
  return null;
}

export async function validationRoutes(app: FastifyInstance, db: Db, eventLog: EventLog): Promise<void> {
  const siteRead = requirePermission("site:read");
  const siteWrite = requirePermission("site:update");
  const applyGuard = requirePermission("validation:create");

  const liveProgram = (id: string) =>
    db
      .select()
      .from(validationPrograms)
      .where(and(eq(validationPrograms.id, id), isNull(validationPrograms.deletedAt)))
      .get();

  const boundUserIds = (programId: string): string[] =>
    db
      .select({ userId: validationProgramUsers.userId })
      .from(validationProgramUsers)
      .where(eq(validationProgramUsers.programId, programId))
      .all()
      .map((r) => r.userId);

  // The setup panel's read: every live program with its bound users.
  app.get("/api/validation/programs", { preHandler: siteRead }, async () => {
    const programs = db.select().from(validationPrograms).where(isNull(validationPrograms.deletedAt)).all();
    return {
      programs: programs.map((p) => ({ ...p, userIds: boundUserIds(p.id) })),
    };
  });

  // Upsert a program (the /setup/site checkbox + panel). Creates the well-known row on
  // first enable; replaces the binding set; signs an attributed config_change when
  // anything actually changed (the entry-presence-bypass precedent — enabling a discount
  // program is fraud-relevant config).
  app.put<{ Params: { id: string }; Body: ProgramBody }>(
    "/api/validation/programs/:id",
    { preHandler: siteWrite },
    async (req, reply) => {
      const id = (req.params.id ?? "").trim();
      if (!ID_RE.test(id)) return reply.code(400).send({ error: "invalid program id" });
      const b = req.body ?? ({} as ProgramBody);
      const bad = validateProgram(b);
      if (bad) return reply.code(400).send({ error: bad });

      const userIds = Array.isArray(b.userIds) ? [...new Set(b.userIds)] : [];
      if (userIds.length) {
        const found = db
          .select({ id: users.id })
          .from(users)
          .where(and(inArray(users.id, userIds), isNull(users.deletedAt)))
          .all();
        if (found.length !== userIds.length) return reply.code(400).send({ error: "unknown user in userIds" });
      }

      const prev = liveProgram(id);
      const prevUserIds = prev ? boundUserIds(id).sort() : [];
      const next = {
        name: String(b.name).trim(),
        mode: b.mode as ValidationMode,
        minutes: b.minutes ?? null,
        percent: b.percent ?? null,
        maxAmountMinor: b.maxAmountMinor ?? null,
        maxPerDay: b.maxPerDay ?? null,
        active: b.active === true,
      };

      if (prev) {
        db.update(validationPrograms).set(next).where(eq(validationPrograms.id, id)).run();
      } else {
        db.insert(validationPrograms).values({ id, ...next }).run();
      }
      db.delete(validationProgramUsers).where(eq(validationProgramUsers.programId, id)).run();
      for (const userId of userIds) {
        db.insert(validationProgramUsers).values({ programId: id, userId }).run();
      }

      // Sign the change (attributed) — enabling/reshaping a discount program is
      // fraud-relevant config. Compare against the previous row + binding set so a
      // no-op save signs nothing.
      const summary = (row: typeof next, ids: string[]) => JSON.stringify({ ...row, userIds: [...ids].sort() });
      const prevSummary = prev
        ? summary(
            { name: prev.name, mode: prev.mode, minutes: prev.minutes, percent: prev.percent,
              maxAmountMinor: prev.maxAmountMinor, maxPerDay: prev.maxPerDay, active: prev.active },
            prevUserIds,
          )
        : null;
      if (prevSummary !== summary(next, userIds)) {
        await eventLog.append({
          type: "config_change",
          source: "manual",
          identity: `validation-program:${id}`,
          payload: {
            setting: `validationProgram.${id}`,
            value: { ...next, userCount: userIds.length },
            prev: prev
              ? { name: prev.name, mode: prev.mode, minutes: prev.minutes, percent: prev.percent,
                  maxAmountMinor: prev.maxAmountMinor, maxPerDay: prev.maxPerDay, active: prev.active }
              : null,
            operator: req.user?.username ?? "unknown",
          },
        });
      }

      const row = liveProgram(id);
      return { ...row, userIds: boundUserIds(id) };
    },
  );

  // The merchant screen's program list: MY bound, active programs.
  app.get("/api/validation/mine", { preHandler: applyGuard }, async (req) => {
    const rows = db
      .select()
      .from(validationPrograms)
      .innerJoin(validationProgramUsers, eq(validationProgramUsers.programId, validationPrograms.id))
      .where(
        and(
          eq(validationProgramUsers.userId, req.user.sub),
          eq(validationPrograms.active, true),
          isNull(validationPrograms.deletedAt),
        ),
      )
      .all();
    return { programs: rows.map((r) => r.validation_programs) };
  });

  // Minimal session view for the merchant screen — deliberately NO money data (the
  // merchant validates; the booth settles): found/open/entry time + the validations
  // already on the session (so the UI can show "already validated" and offer void).
  app.get<{ Params: { identity: string } }>(
    "/api/validation/session/:identity",
    { preHandler: applyGuard },
    async (req, reply) => {
      const identity = (req.params.identity ?? "").trim();
      if (!identity) return reply.code(400).send({ error: "identity required" });
      const rows = db
        .select({ type: ledgerEvents.type, occurredAt: ledgerEvents.occurredAt, payload: ledgerEvents.payload })
        .from(ledgerEvents)
        .where(eq(ledgerEvents.identity, identity))
        .orderBy(ledgerEvents.index)
        .all();
      const entry = rows.find((r) => r.type === "vehicle_entry");
      if (!entry) return { identity, found: false, open: false, enteredAt: null, subscription: false, validations: [] };
      const entryPl = (entry.payload ?? {}) as { permit?: boolean; permitId?: string };
      const subscription = entryPl.permit === true || entryPl.permitId != null;
      const open = !rows.some((r) => r.type === "vehicle_exit" || r.type === "void");
      return {
        identity,
        found: true,
        open,
        enteredAt: entry.occurredAt,
        subscription,
        validations: sessionValidations(db, identity),
      };
    },
  );

  // APPLY: the merchant's one action. Guards, in order: program live+active → the
  // user is BOUND to it → the session is an OPEN TRANSIENT → not already carrying a
  // live application of this program → per-day cap → fixed-amount bounds. Appends the
  // signed validation event with the RESOLVED values.
  app.post<{ Body: ApplyBody }>("/api/validation/apply", { preHandler: applyGuard }, async (req, reply) => {
    const identity = (req.body?.identity ?? "").trim();
    const programId = (req.body?.programId ?? "").trim();
    if (!identity || !programId) return reply.code(400).send({ error: "identity and programId required" });

    const program = liveProgram(programId);
    if (!program || !program.active) return reply.code(404).send({ error: "program not found or inactive" });
    if (!boundUserIds(programId).includes(req.user.sub)) {
      return reply.code(403).send({ error: "you are not bound to this program" });
    }

    // Session state — an open transient (subscriptions are prepaid; nothing to discount).
    const rows = db
      .select({ type: ledgerEvents.type, payload: ledgerEvents.payload })
      .from(ledgerEvents)
      .where(eq(ledgerEvents.identity, identity))
      .orderBy(ledgerEvents.index)
      .all();
    const entry = rows.find((r) => r.type === "vehicle_entry");
    if (!entry) return reply.code(404).send({ error: "no session for ticket" });
    const entryPl = (entry.payload ?? {}) as { permit?: boolean; permitId?: string };
    if (entryPl.permit === true || entryPl.permitId != null) {
      return reply.code(409).send({ error: "subscription sessions cannot be validated" });
    }
    if (rows.some((r) => r.type === "vehicle_exit" || r.type === "void")) {
      return reply.code(409).send({ error: "session is closed" });
    }
    if (liveValidations(db, identity).some((v) => v.programId === programId)) {
      return reply.code(409).send({ error: "this program is already applied to the ticket" });
    }

    // Per-day cap: unvoided applications of this program since LOCAL midnight (the
    // appliance runs in site time).
    if (program.maxPerDay != null) {
      const midnight = new Date();
      midnight.setHours(0, 0, 0, 0);
      const todays = db
        .select({ id: ledgerEvents.id, occurredAt: ledgerEvents.occurredAt, payload: ledgerEvents.payload, type: ledgerEvents.type })
        .from(ledgerEvents)
        .where(eq(ledgerEvents.type, "validation"))
        .all()
        .filter((r) => Date.parse(r.occurredAt) >= midnight.getTime());
      const voidedIds = new Set(
        todays.map((r) => (r.payload as { refId?: string } | null)?.refId).filter(Boolean) as string[],
      );
      const count = todays.filter((r) => {
        const p = (r.payload ?? {}) as { programId?: string; refId?: string };
        return p.programId === programId && !p.refId && !voidedIds.has(r.id);
      }).length;
      if (count >= program.maxPerDay) {
        return reply.code(409).send({ error: "daily cap reached for this program" });
      }
    }

    // Resolve the values off the program row (frozen into the signed event).
    let amountMinor: number | undefined;
    if (program.mode === "fixed") {
      const a = req.body?.amountMinor;
      if (a == null || !Number.isInteger(a) || a <= 0) {
        return reply.code(400).send({ error: "amountMinor (positive integer) required for this program" });
      }
      if (program.maxAmountMinor != null && a > program.maxAmountMinor) {
        return reply.code(400).send({ error: `amount exceeds the program cap (${program.maxAmountMinor})` });
      }
      amountMinor = a;
    }

    const ev = await eventLog.append({
      type: "validation",
      source: "manual",
      identity,
      payload: {
        sessionRef: identity,
        programId,
        programLabel: program.name,
        mode: program.mode,
        ...(program.mode === "timeCredit" && program.minutes != null ? { minutes: program.minutes } : {}),
        ...(program.mode === "percent" && program.percent != null ? { percent: program.percent } : {}),
        ...(amountMinor != null ? { amountMinor } : {}),
        operator: req.user.username,
      },
    });
    return reply.code(201).send({
      ok: true,
      eventId: ev.id,
      programId,
      label: program.name,
      mode: program.mode,
      minutes: program.mode === "timeCredit" ? program.minutes : undefined,
      percent: program.mode === "percent" ? program.percent : undefined,
      amountMinor,
    });
  });

  // VOID my own UNUSED validation (fat-fingered amount / wrong ticket). Append-only:
  // a validation event with refId, never a delete. Refused once a payment consumed it
  // (the settlement already happened — that dispute goes to the booth/admin).
  app.post<{ Body: VoidBody }>("/api/validation/void", { preHandler: applyGuard }, async (req, reply) => {
    const eventId = (req.body?.eventId ?? "").trim();
    const identity = (req.body?.identity ?? "").trim();
    if (!eventId || !identity) return reply.code(400).send({ error: "eventId and identity required" });
    const target = sessionValidations(db, identity).find((v) => v.eventId === eventId);
    if (!target) return reply.code(404).send({ error: "validation not found" });
    if (target.operator !== req.user.username) {
      return reply.code(403).send({ error: "you may only void your own validation" });
    }
    if (target.voided) return reply.code(409).send({ error: "already voided" });
    if (target.consumedBy != null) {
      return reply.code(409).send({ error: "already used in a payment — ask the booth/admin" });
    }
    await eventLog.append({
      type: "validation",
      source: "manual",
      identity,
      payload: {
        sessionRef: identity,
        refId: eventId,
        programId: target.programId,
        programLabel: target.label,
        operator: req.user.username,
      },
    });
    return { ok: true };
  });
}