import { RichTextBlock } from '@shared/kernel/rich-text';

/**
 * Placeholder fields and the PURE linter over them.
 *
 * `lintPlaceholders` is a total, effect-free function of (content, valid set). It
 * runs identically on the client (for live UX) and could run on the server (for
 * authority) — same rules, same config, so the two agree by construction. The FE
 * never STORES its output: diagnostics are a `computed()` over content (see
 * `brief.ts` selectors), the same "derive, don't store" discipline as wizard step
 * validity.
 */

/** A placeholder field the template knows about. `fillable`/`deprecated` default to
    the healthy case; the seed flips them to exercise the not-fillable/deprecated rules. */
export interface PlaceholderDef {
  readonly key: string; // e.g. 'naam_zorgverlener'
  readonly label: string; // human label for the insert menu, e.g. 'Naam zorgverlener'
  readonly autoResolvable: boolean; // server can fill from case data (name, date, …)
  readonly fillable?: boolean; // default true; false → not resolvable for this beroep/case type
  readonly deprecated?: boolean; // default false; true → retired but still referenceable in old snapshots
}

export type DiagnosticSeverity = 'error' | 'warning';

export type DiagnosticCode =
  | 'malformed' // raw braces in a text node (a paste that should have been a chip)
  | 'unknown-placeholder' // well-formed key not in the valid set
  | 'not-fillable' // key exists but isn't resolvable for this case type / beroep
  | 'deprecated' // key was valid once but the template no longer offers it
  | 'unresolved-at-send'; // manual (non-auto-resolvable) placeholder still to be filled

export interface DiagnosticLocation {
  readonly blockId: string;
  readonly paragraphIndex: number;
  readonly nodeIndex: number;
}

export interface Diagnostic {
  readonly severity: DiagnosticSeverity;
  readonly code: DiagnosticCode;
  readonly placeholderKey?: string;
  readonly location: DiagnosticLocation;
  readonly message: string; // human-readable, Dutch
}

/** `error` blocks save (author time) and send (send time); `warning` is surfaced but allowed. */
export function severityOf(code: DiagnosticCode): DiagnosticSeverity {
  switch (code) {
    case 'malformed':
    case 'unknown-placeholder':
    case 'not-fillable':
      return 'error';
    case 'deprecated':
    case 'unresolved-at-send':
      return 'warning';
  }
}

// Raw `{{` or `}}` in text — the only way a malformed placeholder can exist, since
// menu insertion always produces a proper placeholder NODE. Paste safety net.
const RAW_BRACES = /\{\{|\}\}/;

function messageFor(code: DiagnosticCode, key?: string): string {
  switch (code) {
    case 'malformed':
      return $localize`:@@brief.lint.malformed:Deze tekst bevat losse accolades ({{ of }}). Voeg een veld toe via het menu in plaats van het te typen.`;
    case 'unknown-placeholder':
      return $localize`:@@brief.lint.unknown:Onbekend veld “${key}:key:”. Dit veld hoort niet bij dit sjabloon.`;
    case 'not-fillable':
      return $localize`:@@brief.lint.notFillable:Veld “${key}:key:” kan niet worden ingevuld voor dit beroep.`;
    case 'deprecated':
      return $localize`:@@brief.lint.deprecated:Veld “${key}:key:” is verouderd en wordt niet meer aangeboden.`;
    case 'unresolved-at-send':
      return $localize`:@@brief.lint.unresolved:Veld “${key}:key:” wordt handmatig ingevuld en is nog leeg.`;
  }
}

function diag(code: DiagnosticCode, location: DiagnosticLocation, key?: string): Diagnostic {
  return { severity: severityOf(code), code, placeholderKey: key, location, message: messageFor(code, key) };
}

/**
 * Lint one block against the template's placeholder set. Pure: given the same
 * content + valid set + blockId it always returns the same diagnostics, in
 * document order. One diagnostic per node at most (most-severe wins).
 */
export function lintPlaceholders(
  content: RichTextBlock,
  valid: readonly PlaceholderDef[],
  blockId: string,
): Diagnostic[] {
  const byKey = new Map(valid.map((p) => [p.key, p]));
  const out: Diagnostic[] = [];

  content.paragraphs.forEach((p, paragraphIndex) => {
    p.nodes.forEach((n, nodeIndex) => {
      const location: DiagnosticLocation = { blockId, paragraphIndex, nodeIndex };
      if (n.type === 'text') {
        if (RAW_BRACES.test(n.text)) out.push(diag('malformed', location));
        return;
      }
      if (n.type !== 'placeholder') return; // lineBreak — nothing to check

      const def = byKey.get(n.key);
      if (!def) out.push(diag('unknown-placeholder', location, n.key));
      else if (def.fillable === false) out.push(diag('not-fillable', location, n.key));
      else if (def.deprecated) out.push(diag('deprecated', location, n.key));
      else if (!def.autoResolvable) out.push(diag('unresolved-at-send', location, n.key));
      // auto-resolvable & fillable & not deprecated → clean (filled by the server at send)
    });
  });

  return out;
}