import { truncateHead, DEFAULT_MAX_BYTES } from "@earendil-works/pi-coding-agent";

// ---------------------------------------------------------------------------
// Search result formatting
// ---------------------------------------------------------------------------

export function formatSearchResults(results: Array<{
  title?: string;
  url?: string;
  snippet?: string;
  site_name?: string;
  position?: number;
}>): string {
  if (!results.length) return "No results found.";

  const lines: string[] = [];
  lines.push(`Found ${results.length} result(s):\n`);

  for (const r of results) {
    const pos = r.position != null ? `[${r.position}] ` : "";
    const site = r.site_name ? ` (${r.site_name})` : "";
    lines.push(`${pos}${r.title ?? "Untitled"}${site}`);
    if (r.url) lines.push(`  URL: ${r.url}`);
    if (r.snippet) lines.push(`  ${r.snippet}`);
    lines.push("");
  }

  return lines.join("\n");
}

// ---------------------------------------------------------------------------
// Fetch result formatting
// ---------------------------------------------------------------------------

export function formatFetchResults(results: Array<{
  url?: string;
  title?: string;
  description?: string;
  text?: string;
  html?: string;
  error?: string;
}>): string {
  if (!results.length) return "No results returned.";

  const lines: string[] = [];
  lines.push(`Fetched ${results.length} page(s):\n`);

  for (const r of results) {
    lines.push(`## ${r.title ?? r.url ?? "Unknown"}`);
    if (r.url) lines.push(`URL: ${r.url}`);
    if (r.description) lines.push(`Description: ${r.description}`);

    if (r.error) {
      lines.push(`Error: ${r.error}`);
    } else if (r.text) {
      lines.push(r.text);
    } else if (r.html) {
      lines.push("[HTML content available — use format='html' or 'json' to retrieve]");
    } else {
      lines.push("(no extracted content)");
    }
    lines.push("---\n");
  }

  return lines.join("\n");
}

// ---------------------------------------------------------------------------
// Agent run event and structured-result projections
// ---------------------------------------------------------------------------

/** Convert unknown API data into a complete, human-readable Markdown field tree. */
export function formatResultProjection(value: unknown): string {
  if (!isStructuredValue(value)) return formatScalar(value);
  return formatProjectionLines(value, 0).join("\n");
}

function formatProjectionLines(value: Record<string, unknown> | unknown[], depth: number): string[] {
  const indent = "  ".repeat(depth);

  if (Array.isArray(value)) {
    if (!value.length) return [`${indent}- _No items_`];

    return value.flatMap((item, index) => {
      if (!isStructuredValue(item)) return `${indent}- ${formatScalar(item)}`;
      return [`${indent}- Item ${index + 1}:`, ...formatProjectionLines(item, depth + 1)];
    });
  }

  const entries = Object.entries(value);
  if (!entries.length) return [`${indent}- _No fields_`];

  return entries.flatMap(([key, item]) => {
    const label = `**${escapeMarkdown(key)}**`;
    if (!isStructuredValue(item)) return `${indent}- ${label}: ${formatScalar(item)}`;
    return [`${indent}- ${label}:`, ...formatProjectionLines(item, depth + 1)];
  });
}

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

function formatScalar(value: unknown): string {
  if (value === null) return "none";
  if (value === undefined) return "not provided";
  if (typeof value === "string" || typeof value === "number" || typeof value === "boolean" || typeof value === "bigint") {
    return String(value);
  }
  return "unavailable";
}

function escapeMarkdown(value: string): string {
  return value.replace(/[\\`*_[\]<>]/g, "\\$&");
}

function formatEventPayload(value: unknown): string {
  const projection = formatResultProjection(value);
  return isStructuredValue(value) ? `\n${projection}` : ` ${projection}`;
}

export function formatAgentEvent(event: { type: string; data: unknown }): string {
  switch (event.type) {
    case "STARTED":
      return "🚀 Agent started...";
    case "STREAMING_URL":
      return typeof event.data === "string"
        ? `🌐 Browser preview: ${event.data}`
        : "🌐 Browser session active";
    case "PROGRESS":
      return `⏳${formatEventPayload(event.data)}`;
    case "COMPLETE":
      return "✅ Agent completed.";
    case "ERROR":
      return `❌ Error:${formatEventPayload(event.data)}`;
    default:
      return `${event.type}:${formatEventPayload(event.data)}`;
  }
}

// ---------------------------------------------------------------------------
// Truncation wrapper around pi's built-in
// ---------------------------------------------------------------------------

export function truncateOutput(text: string, maxBytes?: number): string {
  const limit = maxBytes ?? DEFAULT_MAX_BYTES;
  const result = truncateHead(text, { maxBytes: limit });
  // truncateHead returns TruncationResult { content, truncated, ... }
  return typeof result === "string" ? result : (result?.content ?? String(result));
}