/**
 * Per-run model selection & role-based routing.
 *
 * ADR-0017 consequence: role-based model routing (different run kinds default
 * to different models) is a **product/admin configuration** concern, not a spec
 * invariant. This registry is the seam for that config; the concrete policy
 * (which models are admin-enabled, which role maps to which default) is `OPEN`
 * here — decided by admin settings + ADR, not hard-coded.
 */

/** Coarse run role, used to pick a default model. Open set: add as product grows. */
export type RunRole = "draft" | "review" | "triage";

/** A model the admin has enabled for use by the Hub. */
export interface ModelEntry {
  readonly id: string;
  /** Human label for the teacher-side switcher UX. */
  readonly label: string;
  /** True when the model is known to support tool use reliably. */
  readonly toolCapable: boolean;
}

export interface ModelRegistry {
  /** All models admin-enabled for this Hub instance. */
  list(): readonly ModelEntry[];
  /** Default model id for a given run role, if a routing rule exists. */
  defaultFor(role: RunRole): string | undefined;
}

/**
 * A simple in-memory registry. Real wiring reads from admin settings / DB; this
 * is the skeleton seam. The policy (role→model map) is intentionally pluggable.
 */
export class InMemoryModelRegistry implements ModelRegistry {
  private readonly models: readonly ModelEntry[];
  private readonly defaults: Map<RunRole, string>;

  constructor(models: readonly ModelEntry[], defaults: Partial<Record<RunRole, string>> = {}) {
    this.models = models;
    this.defaults = new Map(
      (Object.entries(defaults) as [RunRole, string][]).filter(([, v]) => v !== undefined),
    );
  }

  list(): readonly ModelEntry[] {
    return this.models;
  }

  defaultFor(role: RunRole): string | undefined {
    return this.defaults.get(role);
  }

  /** Resolve a model id, falling back to the role default, then the first enabled. */
  resolve(requested: string | undefined, role: RunRole): string {
    if (requested !== undefined && this.models.some((m) => m.id === requested)) {
      return requested;
    }
    const d = this.defaultFor(role);
    if (d !== undefined) return d;
    const first = this.models[0];
    if (first === undefined) throw new Error("no models enabled for this Hub");
    return first.id;
  }
}