/** In-memory ring buffer of multi-agent guidance-injection / effort-cap log lines.
 *
 * Injection debug lines were previously console-only, so the GUI had an "Injection log"
 * toggle with nothing to display. This buffer mirrors the provider debug buffer so the
 * management API and GUI can tail injection lines the same way. Callers keep their own
 * `isInjectionDebugEnabled()` guard; this module only stores what it is given. */

import type { DebugLogEntry } from "./debug-log-buffer";
import { retainedUtf8Bytes, truncateRetainedUtf8 } from "./admission";
import { enforceAppOwnedMemoryBudget } from "./app-owned-memory";

const MAX_LINES = 2_000;
const MAX_DEBUG_LINE_BYTES = 16 * 1024;
const buffer: DebugLogEntry[] = [];
let nextSeq = 1;
let bufferBytes = 0;

function removeOldestEntry(): number {
  const entry = buffer.shift();
  if (!entry) return 0;
  const bytes = retainedUtf8Bytes(entry.line);
  bufferBytes -= bytes;
  return bytes;
}

/** Append a line to the injection buffer and echo it to the server console. */
export function injectionDebugLog(line: string): void {
  const retainedLine = truncateRetainedUtf8(line, MAX_DEBUG_LINE_BYTES);
  const entry: DebugLogEntry = { seq: nextSeq++, at: Date.now(), line: retainedLine };
  buffer.push(entry);
  bufferBytes += retainedUtf8Bytes(retainedLine);
  while (buffer.length > MAX_LINES) removeOldestEntry();
  enforceAppOwnedMemoryBudget();
  console.log(line);
}

export function getInjectionDebugLogEntries(options?: { after?: number; limit?: number }): DebugLogEntry[] {
  const after = options?.after ?? 0;
  const limit = options?.limit ?? 500;
  const filtered = after > 0 ? buffer.filter(entry => entry.seq > after) : buffer;
  if (filtered.length <= limit) return filtered;
  return filtered.slice(-limit);
}

export function injectionBufferMetrics(): { entries: number; bytes: number; oldestAt: number | null } {
  return { entries: buffer.length, bytes: bufferBytes, oldestAt: buffer[0]?.at ?? null };
}

export function evictOldestInjectionEntryForBudget(): number {
  return removeOldestEntry();
}

/** Test isolation. */
export function resetInjectionDebugLogBufferForTests(): void {
  buffer.length = 0;
  bufferBytes = 0;
  nextSeq = 1;
}