/**
 * Model and thinking-level change detection.
 * Sends model_update only when values actually change.
 */
import type { BridgeContext } from "./bridge-context.js";
import { getCurrentModelString } from "./bridge-context.js";
import { gatherGitInfo, gatherJjInfo } from "./vcs-info.js";

/**
 * Send model_update if model or thinking level has changed since last send.
 */
export function sendModelUpdateIfChanged(bc: BridgeContext): void {
  const model = getCurrentModelString(bc);
  const thinkingLevel = (bc.pi as any).getThinkingLevel?.() ?? undefined;
  if (model === bc.lastModel && thinkingLevel === bc.lastThinkingLevel) return;
  bc.lastModel = model;
  bc.lastThinkingLevel = thinkingLevel;
  if (model) {
    bc.connection.send({
      type: "model_update",
      sessionId: bc.sessionId,
      model,
      thinkingLevel,
    });
  }
}

/**
 * Send session_name_update if name has changed since last send.
 */
export function sendSessionNameIfChanged(bc: BridgeContext): void {
  const name = bc.pi.getSessionName() ?? "";
  if (name === bc.lastSessionName) return;
  bc.lastSessionName = name;
  bc.connection.send({
    type: "session_name_update",
    sessionId: bc.sessionId,
    name,
  });
}

/**
 * Send git_info_update if branch or PR has changed since last send.
 */
export function sendGitInfoIfChanged(bc: BridgeContext, cwd: string): void {
  const info = gatherGitInfo(cwd);
  if (!info) return;
  if (info.gitBranch === bc.lastGitBranch && info.gitPrNumber === bc.lastGitPrNumber) return;
  bc.lastGitBranch = info.gitBranch;
  bc.lastGitPrNumber = info.gitPrNumber;
  bc.connection.send({
    type: "git_info_update",
    sessionId: bc.sessionId,
    ...info,
  });
}

/**
 * Reset the change-detection caches that aren't persisted on the server
 * side, so a server-restart-driven reconnect re-sends them. `gitBranch`
 * is already persisted to `.meta.json` so it's tolerable for a tick of
 * staleness; `jjState` is intentionally NOT persisted (live tool state)
 * and must be re-emitted on every reconnect.
 * See change: add-jj-workspace-plugin.
 */
export function resetReconnectCaches(bc: BridgeContext): void {
  bc.lastJjStateJson = undefined;
  // Defensive: also reset git so a reconnect through a stale state cache
  // doesn't surface stale branch info if .meta.json wasn't persisted yet.
  bc.lastGitBranch = undefined;
  bc.lastGitPrNumber = undefined;
}

/**
 * Send jj_state_update if the cwd's jj state has changed since last send.
 * Sends `null` to clear when the session leaves a jj repo (cwd switch).
 * No-op when there's nothing to clear and nothing to send.
 * See change: add-jj-workspace-plugin.
 */
export function sendJjStateIfChanged(bc: BridgeContext, cwd: string): void {
  const state = gatherJjInfo(cwd);
  const nextJson = state ? JSON.stringify(state) : "";
  if (nextJson === (bc.lastJjStateJson ?? "")) return;
  bc.lastJjStateJson = nextJson;
  bc.connection.send({
    type: "jj_state_update",
    sessionId: bc.sessionId,
    jjState: state ?? null,
  });
}