import type { SessionEntry } from "@earendil-works/pi-coding-agent";
import type { ApplyLedger, OwnershipState } from "./types.ts";

export const APPLY_ENTRY_TYPE = "pi-tree-labeler.apply";

function isLedger(value: unknown): value is ApplyLedger {
  if (!value || typeof value !== "object") return false;
  const record = value as Partial<ApplyLedger>;
  if (record.version !== 1 || typeof record.runId !== "string" || !Array.isArray(record.changes)) return false;
  return record.changes.every((change) => Boolean(change)
    && typeof change.targetId === "string"
    && typeof change.label === "string"
    && typeof change.labelEntryId === "string"
    && (change.previousLabel === undefined || typeof change.previousLabel === "string"));
}

export function reconstructOwnership(entries: SessionEntry[]): OwnershipState {
  const latestLabelEntryByTarget = new Map<string, { id: string; label: string | undefined }>();
  const seenLabelsById = new Map<string, { targetId: string; label: string | undefined }>();
  const ownedLabelEntryIds = new Set<string>();

  for (const entry of entries) {
    if (entry.type === "label") {
      const label = { targetId: entry.targetId, label: entry.label };
      seenLabelsById.set(entry.id, label);
      latestLabelEntryByTarget.set(entry.targetId, { id: entry.id, label: entry.label });
      continue;
    }
    if (entry.type === "custom" && entry.customType === APPLY_ENTRY_TYPE && isLedger(entry.data)) {
      for (const change of entry.data.changes) {
        const referenced = seenLabelsById.get(change.labelEntryId);
        if (referenced?.targetId === change.targetId && referenced.label === change.label) {
          ownedLabelEntryIds.add(change.labelEntryId);
        }
      }
    }
  }

  const manuallyClearedTargets = new Set<string>();
  for (const [targetId, latest] of latestLabelEntryByTarget) {
    if (latest.label === undefined && !ownedLabelEntryIds.has(latest.id)) manuallyClearedTargets.add(targetId);
  }

  return { latestLabelEntryByTarget, ownedLabelEntryIds, manuallyClearedTargets };
}

export function classifyOwnership(targetId: string, state: OwnershipState): "owned" | "manual" | "none" {
  const latest = state.latestLabelEntryByTarget.get(targetId);
  if (!latest) return "none";
  return state.ownedLabelEntryIds.has(latest.id) ? "owned" : "manual";
}