export interface InflightRequest {
  id?: string;
  model: string;
  req_path?: string;
  method?: string;
  timestamp?: string;
  elapsed_ms?: number;
}

export interface ModelState {
  id: string;
  state: string;
}

export type FeedEvent =
  | { type: "inflight"; operation: "snapshot" | "add"; requests: InflightRequest[] }
  | { type: "inflight"; operation: "remove"; id: string }
  | { type: "activity"; id: number }
  | { type: "modelStatus"; models: ModelState[] };

export type ModelRuntimeState = "stopped" | "loading" | "ready";

export class InflightTracker {
  private requests = new Map<string, string>();
  private states = new Map<string, ModelRuntimeState>();

  apply(event: FeedEvent): void {
    if (event.type === "inflight") {
      if (event.operation === "snapshot") {
        this.requests = new Map<string, string>();
        for (const r of event.requests) if (r.id) this.requests.set(r.id, r.model);
      } else if (event.operation === "add") {
        for (const r of event.requests) if (r.id) this.requests.set(r.id, r.model);
      } else if (event.operation === "remove") {
        this.requests.delete(event.id);
      }
    } else if (event.type === "modelStatus") {
      for (const m of event.models) this.states.set(m.id, normalizeState(m.state));
    }
  }

  count(modelId: string): number {
    let n = 0;
    for (const model of this.requests.values()) if (model === modelId) n++;
    return n;
  }

  total(): number {
    return this.requests.size;
  }

  state(modelId: string): ModelRuntimeState | undefined {
    return this.states.get(modelId);
  }
}

function normalizeState(state: string): ModelRuntimeState {
  if (state === "ready") return "ready";
  if (state === "loading") return "loading";
  return "stopped";
}