import { Injectable, computed, inject, signal } from '@angular/core';
import { Result } from '@shared/kernel/fp';
import { createStore } from '@shared/application/store';
import { ActionState, SaveState } from '@shared/application/action-state';
import { createHistory } from '@shared/application/history';
import { createDebouncedSave } from '@shared/application/debounced-save';
import { machineRemoteData } from '@shared/application/machine-remote-data';
import {
  Brief,
  CaseContext,
  allDiagnostics,
  canSubmit,
  hasBlockingErrors,
  unresolvedPlaceholders,
} from '@brief/domain/brief';
import { BriefMsg, BriefState, initial, reduce } from '@brief/domain/brief.machine';
import { BlockDiffKind, changedBlocks, diffBlocks } from '@brief/domain/brief-diff';
import { OrgTemplate } from '@brief/domain/org-template';
import { BriefAdapter, BriefView } from '@brief/infrastructure/brief.adapter';
import { LetterPreviewAdapter } from '@brief/infrastructure/letter-preview.adapter';
import { RevealBigNummerAdapter } from '@brief/infrastructure/reveal-bignummer.adapter';
import { uploadContentUrl } from '@shared/upload/upload.adapter';
import { PendingSave, registerPendingSave } from '@shared/application/pending-saves';

/**
 * Root singleton for the letter: the Elm store (Model + dispatch), the derived
 * read-model, and the commands (effects) that call the adapter and dispatch the
 * outcome. Mirrors `BigProfileStore`. All of `canEdit`/`canApprove`/`canReject`/
 * `canSend`, `diagnostics`, `unresolved`, `canSubmit` are DERIVED here — never
 * stored. The permission flags come from the server's decision DTO (PRD-0002 phase
 * P1) via `BriefState.loaded.decisions` — this store never computes them itself.
 */
@Injectable({ providedIn: 'root' })
export class BriefStore implements PendingSave {
  private adapter = inject(BriefAdapter);
  private previewAdapter = inject(LetterPreviewAdapter);
  private revealAdapter = inject(RevealBigNummerAdapter);
  private store = createStore<BriefState, BriefMsg>(initial, reduce);

  readonly model = this.store.model;

  private actionState = signal<ActionState>({ tag: 'Idle' });
  readonly busy = computed(() => this.actionState().tag === 'Busy');
  readonly lastError = computed(() => {
    const s = this.actionState();
    return s.tag === 'Failed' ? s.error : null;
  });

  /** Surfaced autosave state for the indicator + aria-live region. */
  readonly saveState = signal<SaveState>({ tag: 'Idle' });

  /** Undo/redo is SHELL state, not machine state (WP-27): a `createHistory` stack of
      `Brief` snapshots (WP-31 extracted the mechanics). Only CONTENT edits are recorded
      (they flow through `edit()`); status transitions never enter history, or undo would
      replay workflow state. Restore re-dispatches the existing `Seed` Msg — zero machine
      changes. */
  private history = createHistory<Brief>(50);
  readonly canUndo = this.history.canUndo;
  readonly canRedo = this.history.canRedo;

  /** The letter as it stood when it was REJECTED, captured shell-side (WP-27). The
      approver diffs it against the resubmitted letter. POC limit: in-memory only, so a
      full page reload loses it — a real system would persist the rejected revision. */
  private rejectionSnapshot = signal<Brief | null>(null);
  /** Changed/added/removed blocks since rejection — a pure fold over two snapshots. */
  readonly blockDiffs = computed<ReadonlyMap<string, BlockDiffKind>>(() => {
    const before = this.rejectionSnapshot();
    const after = this.brief();
    return before && after ? changedBlocks(diffBlocks(before, after)) : new Map();
  });
  /** Count of blocks removed since rejection — badged as a summary, since a removed
      block no longer renders inline. */
  readonly removedSinceReject = computed(
    () => [...this.blockDiffs().values()].filter((k) => k === 'removed').length,
  );
  readonly hasRejectionDiff = computed(() => this.blockDiffs().size > 0);

  /** The org template the letter renders with (WP-24). Server-owned appearance data,
      not letter state — held beside the machine, never inside it (`brief.machine.ts`
      stays untouched by design). Set from every server view that carries it. */
  readonly orgTemplate = signal<OrgTemplate | null>(null);

  /** The case (zorgverlener + aanvraag) this letter concerns — server-joined context for
      the behandel scherm header, not letter state. Set from every server view. */
  readonly caseContext = signal<CaseContext | null>(null);

  /** The org logo's content URL for the letterhead, or null when the template has none. */
  readonly logoUrl = computed<string | null>(() => {
    const id = this.orgTemplate()?.logoDocumentId;
    return id ? uploadContentUrl(id) : null;
  });

  /** The load lifecycle as `RemoteData`, for `<app-async>` — the machine keeps
      owning the letter's own domain lifecycle (draft/submitted/approved/…); this is
      purely a projection of its loading/failed tags onto the shared async seam. */
  readonly remoteData = computed(() => machineRemoteData(this.model()));

  private brief = computed<Brief | null>(() => {
    const s = this.model();
    return s.tag === 'loaded' ? s.brief : null;
  });

  readonly canEdit = computed(() => this.decisions()?.canEdit ?? false);
  readonly canApprove = computed(() => this.decisions()?.canApprove ?? false);
  readonly canReject = computed(() => this.decisions()?.canReject ?? false);
  readonly canSend = computed(() => this.decisions()?.canSend ?? false);
  /** Field-level PII reveal (PRD-0002 §5c), deny-by-default like the action gates. */
  readonly canRevealBigNummer = computed(() => this.decisions()?.canRevealBigNummer ?? false);

  private decisions = computed(() => {
    const s = this.model();
    return s.tag === 'loaded' ? s.decisions : null;
  });
  readonly diagnostics = computed(() => (this.brief() ? allDiagnostics(this.brief()!) : []));
  readonly unresolved = computed(() => (this.brief() ? unresolvedPlaceholders(this.brief()!) : []));
  /** Submit is allowed only when required sections are filled AND no blocking errors. */
  readonly canSubmit = computed(() => {
    const b = this.brief();
    return !!b && canSubmit(b) && !hasBlockingErrors(this.diagnostics());
  });

  async load() {
    const r = await this.adapter.load();
    if (r.ok) {
      this.orgTemplate.set(r.value.orgTemplate);
      this.caseContext.set(r.value.caseContext);
      this.history.clear();
      this.store.dispatch({ tag: 'BriefLoaded', ...r.value });
    } else {
      this.store.dispatch({ tag: 'BriefLoadFailed', reason: r.error });
    }
  }

  /** An edit: apply it optimistically in the pure reducer, then debounce-save. Records
      an undo step only when the reducer actually changed the brief (a no-op edit — e.g.
      a locked section — returns the same value and leaves no dead history step). */
  edit(msg: BriefMsg) {
    const before = this.brief();
    this.store.dispatch(msg);
    const after = this.brief();
    // Record only a real change: a no-op edit (e.g. a locked section) returns the same
    // value and leaves no dead history step.
    if (before && after && after !== before) this.history.record(before);
    this.debouncedSave.schedule();
  }

  /** Undo/redo: restore a snapshot via the existing `Seed` Msg, then autosave. */
  undo() {
    this.restore((current) => this.history.undo(current));
  }
  redo() {
    this.restore((current) => this.history.redo(current));
  }
  private restore(step: (current: Brief) => Brief | undefined) {
    const s = this.model();
    if (s.tag !== 'loaded') return;
    const target = step(s.brief);
    if (target === undefined) return;
    this.store.dispatch({ tag: 'Seed', state: { ...s, brief: target } });
    this.debouncedSave.schedule();
  }

  constructor() {
    // Register so the CanDeactivate guard / beforeunload handler can flush a pending
    // debounced edit before navigation or unload (see pending-saves.ts).
    registerPendingSave(this);
  }

  // 600ms debounced autosave (the server is the store of record). Timer mechanics live in
  // the shared helper; `flushSave` below is the store-specific write + save-state (WP-31).
  private debouncedSave = createDebouncedSave({
    canSave: () => this.canEdit(),
    flush: () => this.flushSave(),
  });
  /** PendingSave: delegate to the debounce helper so the guard/unload can flush. */
  hasPendingSave = () => this.debouncedSave.hasPendingSave();
  flushPending = () => this.debouncedSave.flushPending();
  private async flushSave() {
    const b = this.brief();
    if (!b) return;
    this.saveState.set({ tag: 'Saving' });
    const r = await this.adapter.save(b.sections);
    if (r.ok) {
      this.saveState.set({ tag: 'Saved' });
    } else {
      this.actionState.set({ tag: 'Failed', error: r.error });
      this.saveState.set({ tag: 'Error' });
    }
  }

  /** Retry a failed autosave — reuses the existing flush path, no new state (WP-27). */
  retrySave() {
    void this.flushSave();
  }

  /** Demo "start over": recreate the brief server-side and load the fresh view. */
  async resetDemo() {
    this.actionState.set({ tag: 'Busy' });
    this.debouncedSave.cancel();
    const r = await this.adapter.reset();
    this.saveState.set({ tag: 'Idle' });
    if (r.ok) {
      this.actionState.set({ tag: 'Idle' });
      this.orgTemplate.set(r.value.orgTemplate);
      this.caseContext.set(r.value.caseContext);
      this.history.clear();
      this.rejectionSnapshot.set(null);
      this.store.dispatch({ tag: 'BriefLoaded', ...r.value });
    } else {
      this.actionState.set({ tag: 'Failed', error: r.error });
    }
  }

  submit = () => this.transition(() => this.adapter.submit());
  approve = () => this.transition(() => this.adapter.approve());
  reject = (comments: string) => this.transition(() => this.adapter.reject(comments));
  send = () => this.transition(() => this.adapter.send());

  /** Explicit action, never a live re-render (PRD §8): opens the server-composed
      letter in a new tab. ponytail: the blob URL is never revoked — it's cheap and
      the tab outlives this call; not worth a teardown hook for a POC. */
  async previewLetter() {
    this.actionState.set({ tag: 'Busy' });
    const r = await this.previewAdapter.preview();
    if (!r.ok) {
      this.actionState.set({ tag: 'Failed', error: r.error });
      return;
    }
    this.actionState.set({ tag: 'Idle' });
    window.open(URL.createObjectURL(r.value), '_blank');
  }

  /** Reveal the masked case BIG-nummer (PRD-0002 §5c). Server re-checks the capability
      + step-up and audits the attempt; on success we swap the masked value in the
      already-loaded caseContext (a field update, not a reload). The step-up gesture
      itself is the UI's concern — this command just runs the audited server call. */
  async revealBigNummer() {
    const r = await this.revealAdapter.reveal();
    if (!r.ok) {
      this.actionState.set({ tag: 'Failed', error: r.error });
      return;
    }
    this.caseContext.update((c) => (c ? { ...c, bigNummer: r.value } : c));
  }

  // A transition: flush any pending save, call the server (authoritative), then mirror
  // the returned status through the pure reducer's guarded transition.
  private async transition(action: () => Promise<Result<string, BriefView>>) {
    this.actionState.set({ tag: 'Busy' });
    this.debouncedSave.cancel();
    await this.flushSave();
    const r = await action();
    if (!r.ok) {
      this.actionState.set({ tag: 'Failed', error: r.error });
      return;
    }
    this.actionState.set({ tag: 'Idle' });
    this.applyServerStatus(r.value);
  }

  private applyServerStatus(view: BriefView) {
    // `send` pins the org-template version server-side — mirror whatever came back.
    this.orgTemplate.set(view.orgTemplate);
    this.caseContext.set(view.caseContext);
    const { brief, decisions } = view;
    const s = brief.status;
    switch (s.tag) {
      case 'submitted':
        this.store.dispatch({ tag: 'Submitted', by: s.submittedBy, at: s.submittedAt, decisions });
        break;
      case 'approved':
        this.store.dispatch({ tag: 'Approved', by: s.approvedBy, at: s.approvedAt, decisions });
        break;
      case 'rejected':
        // Capture the letter as-rejected for the resubmission diff (WP-27). This is the
        // "before" snapshot the approver later compares against.
        this.rejectionSnapshot.set(brief);
        this.store.dispatch({
          tag: 'Rejected',
          by: s.rejectedBy,
          at: s.rejectedAt,
          comments: s.comments,
          decisions,
        });
        break;
      case 'sent':
        this.store.dispatch({ tag: 'Sent', at: s.sentAt, decisions });
        break;
      case 'draft':
        // reopened by a save on a rejected letter — reducer already handled it locally.
        break;
    }
  }
}