/**
 * Text extraction utilities for Claude Agent SDK events.
 *
 * Provides defensive multi-level extraction to handle evolving SDK event shapes.
 */

function isRecord(value: unknown): value is Record<string, unknown> {
  return !!value && typeof value === "object" && !Array.isArray(value);
}

function extractTextFromContent(value: unknown): string | undefined {
  if (typeof value === "string") return value;

  // Common Claude-style content: [{type:"text", text:"..."}]
  if (Array.isArray(value)) {
    const parts: string[] = [];
    for (const entry of value) {
      if (typeof entry === "string") {
        parts.push(entry);
        continue;
      }
      if (!isRecord(entry)) continue;
      const text = entry.text;
      if (typeof text === "string" && text.trim()) parts.push(text);
    }
    const joined = parts.join("\n").trim();
    return joined || undefined;
  }

  if (isRecord(value)) {
    // Some SDKs emit {text:"..."} or {delta:"..."}.
    const text = value.text;
    if (typeof text === "string" && text.trim()) return text;
    const delta = value.delta;
    if (typeof delta === "string" && delta.trim()) return delta;

    // Some SDKs nest deltas (e.g. Claude stream_event: { event: { delta: { text } } }).
    const nestedDelta = extractTextFromContent(delta);
    if (nestedDelta) return nestedDelta;

    const event = value.event;
    const nestedEvent = extractTextFromContent(event);
    if (nestedEvent) return nestedEvent;

    const content = value.content;
    const nested = extractTextFromContent(content);
    if (nested) return nested;
  }

  return undefined;
}

/**
 * Best-effort extraction of human-readable text from Claude Agent SDK events.
 * We keep this defensive because the SDK event shapes may evolve.
 */
export function extractTextFromClaudeAgentSdkEvent(event: unknown): string | undefined {
  if (typeof event === "string") return event;
  if (!isRecord(event)) return undefined;

  // Direct text-ish fields.
  const direct = extractTextFromContent(event);
  if (direct) return direct;

  // Common wrapper shapes: {message:{...}}, {data:{...}}.
  const message = event.message;
  const fromMessage = extractTextFromContent(message);
  if (fromMessage) return fromMessage;

  const data = event.data;
  const fromData = extractTextFromContent(data);
  if (fromData) return fromData;

  // Nested message/data objects with content.
  if (isRecord(message)) {
    const fromMessageContent = extractTextFromContent(message.content);
    if (fromMessageContent) return fromMessageContent;
  }
  if (isRecord(data)) {
    const fromDataContent = extractTextFromContent(data.content);
    if (fromDataContent) return fromDataContent;
  }

  return undefined;
}