// `dynamic-trim` — agent-driven tool_result rewrite tool.
//
// The agent picks a past toolResult block by toolCallId and supplies a
// short `replacement` string; on the next turn boundary (agent_end hook)
// the session jsonl is rewritten so that:
//
//   1. The target toolResult.content[].text becomes
//      "[trimmed by self] <replacement>"
//   2. The dynamic-trim call's OWN tool_use input is rewritten to
//      {"tool_call_id":"<id>","_self_compacted":true}
//      so the bulky replacement text doesn't sit duplicated in two places.
//
// Operates directly on <openclaw>/agents/<agentId>/sessions/<sid>.jsonl.
// No faithful audit — irreversible by design (re-run the original tool
// if you trim wrong). See WORKFLOW-TOOLS-COMPLETION-REQUEST.md in Plexum
// docs/ for the cross-runtime contract.

import * as fs from 'node:fs';
import * as os from 'node:os';
import * as path from 'node:path';

export interface SessionRewriteCtx {
  agentDir?: string;
  agentId?: string;
  sessionId?: string;
}

const TRIM_SENTINEL = '[trimmed by self]';

function openclawRoot(): string {
  const env = process.env.OPENCLAW_PATH;
  if (env) return env;
  const home = process.env.HOME || os.homedir();
  return path.join(home, '.openclaw');
}

function resolveSessionFile(ctx: SessionRewriteCtx): string {
  if (!ctx.sessionId) {
    throw new Error('session context missing sessionId (no active session?)');
  }
  const candidates: string[] = [];
  if (ctx.agentId) {
    candidates.push(
      path.join(openclawRoot(), 'agents', ctx.agentId, 'sessions', `${ctx.sessionId}.jsonl`),
    );
  }
  if (ctx.agentDir) {
    candidates.push(path.join(ctx.agentDir, 'sessions', `${ctx.sessionId}.jsonl`));
    const stripped = ctx.agentDir.replace(/\/agent$/, '');
    if (stripped !== ctx.agentDir) {
      candidates.push(path.join(stripped, 'sessions', `${ctx.sessionId}.jsonl`));
    }
  }
  for (const f of candidates) {
    if (fs.existsSync(f)) return f;
  }
  throw new Error(
    `session file not found for sessionId=${ctx.sessionId}; tried: ${candidates.join(', ')}`,
  );
}

interface MessageEvent {
  type?: string;
  message?: {
    role?: string;
    toolCallId?: string;
    toolName?: string;
    content?: Array<{
      type?: string;
      text?: string;
      id?: string;         // toolCall block id
      name?: string;       // toolCall block name
      arguments?: unknown; // toolCall block arguments — what we self-compact
    }>;
  };
}

export interface DynamicTrimParams {
  tool_call_id: string;
  replacement?: string;
}

export interface DynamicTrimResult {
  ok: true;
  status: 'queued';
  tool_call_id: string;
  self_compacted: true;
  applies_at: 'agent_end';
  note: string;
}

interface QueuedTrim {
  targetCallId: string;   // the past tool_result we want to rewrite
  replacement?: string;   // agent-supplied summary
  selfCallId: string;     // the dynamic-trim's OWN tool_use id; gets self-compacted
}

// Module-scope queue keyed by absolute session file path. Drained from
// the `agent_end` hook (see index.ts). Writing during tool execute trips
// openclaw's session-file fence (EmbeddedAttemptSessionTakeoverError)
// because the fingerprint check around releaseForPrompt rejects third-
// party writes; agent_end fires AFTER that fence window closes.
const trimQueue = new Map<string, QueuedTrim[]>();

/**
 * Enqueue a dynamic-trim mutation. Returns synchronously to the agent
 * with a "queued" status; the actual file rewrite happens on agent_end.
 */
export function queueDynamicTrim(
  ctx: SessionRewriteCtx,
  params: DynamicTrimParams,
  selfCallId: string,
): DynamicTrimResult {
  if (!params.tool_call_id) {
    throw new Error('missing required parameter: tool_call_id');
  }
  if (!selfCallId) {
    throw new Error(
      'dynamic-trim: cannot identify self tool_use id (openclaw runtime should pass it to execute as first arg)',
    );
  }
  const sessionFile = resolveSessionFile(ctx);
  // Validate the target id BEFORE queueing — otherwise agent learns of the
  // mistake only in the drain log. Weak models occasionally pass topic ids
  // / fact ids / small integers thinking they're tool_use ids.
  if (!sessionHasToolResult(sessionFile, params.tool_call_id)) {
    throw new Error(
      `tool_call_id "${params.tool_call_id}" does not match any toolResult in this session. ` +
        `Find the opaque "call_function_*_N" id in your own prior assistant messages — ` +
        `topic ids, fact ids, and small integers will not work here.`,
    );
  }
  const list = trimQueue.get(sessionFile) ?? [];
  list.push({
    targetCallId: params.tool_call_id,
    replacement: params.replacement,
    selfCallId,
  });
  trimQueue.set(sessionFile, list);
  return {
    ok: true,
    status: 'queued',
    tool_call_id: params.tool_call_id,
    self_compacted: true,
    applies_at: 'agent_end',
    note:
      'Trim queued. On this turn end the target tool_result text is shrunk AND this dynamic-trim ' +
      'call\'s own tool_use input is replaced with {tool_call_id, _self_compacted:true}. ' +
      'Effect visible in next turn\'s context.',
  };
}

function sessionHasToolResult(sessionFile: string, toolCallId: string): boolean {
  const raw = fs.readFileSync(sessionFile, 'utf8');
  const needle = `"toolCallId":"${toolCallId}"`;
  if (!raw.includes(needle)) return false;
  for (const line of raw.split('\n')) {
    if (!line.includes(needle)) continue;
    try {
      const obj = JSON.parse(line) as MessageEvent;
      if (
        obj?.type === 'message' &&
        obj?.message?.role === 'toolResult' &&
        obj?.message?.toolCallId === toolCallId
      ) {
        return true;
      }
    } catch {
      /* skip malformed */
    }
  }
  return false;
}

export interface DrainResult {
  session_file: string;
  applied: number;
  skipped: number;
  trimmed_bytes: number;
  self_compacted: number; // how many of the dynamic-trim tool_use inputs we shrank
  errors: string[];
}

export async function drainTrimQueueForSession(
  sessionFile: string,
): Promise<DrainResult | null> {
  const queued = trimQueue.get(sessionFile);
  if (!queued || queued.length === 0) return null;
  trimQueue.delete(sessionFile);

  if (!fs.existsSync(sessionFile)) {
    return {
      session_file: sessionFile,
      applied: 0,
      skipped: queued.length,
      trimmed_bytes: 0,
      self_compacted: 0,
      errors: [`session file vanished: ${sessionFile}`],
    };
  }

  const raw = await fs.promises.readFile(sessionFile, 'utf8');
  const lines = raw.split('\n');

  // Build lookup maps.
  // targetsByCallId: tool_result id → queued mutation
  // selfByCallId:    dynamic-trim tool_use id → queued mutation (for self-compact)
  const targetsByCallId = new Map<string, QueuedTrim>();
  const selfByCallId = new Map<string, QueuedTrim>();
  for (const q of queued) {
    targetsByCallId.set(q.targetCallId, q);
    selfByCallId.set(q.selfCallId, q);
  }

  let applied = 0;
  let skipped = 0;
  let trimmedBytes = 0;
  let selfCompacted = 0;
  const errors: string[] = [];

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    if (!line) continue;
    let obj: MessageEvent;
    try {
      obj = JSON.parse(line) as MessageEvent;
    } catch {
      continue;
    }
    if (obj?.type !== 'message') continue;
    const role = obj.message?.role;

    // (A) toolResult rewrite — target
    if (role === 'toolResult') {
      const callId = obj.message?.toolCallId;
      if (!callId) continue;
      const q = targetsByCallId.get(callId);
      if (!q) continue;
      const content = obj.message?.content;
      if (!Array.isArray(content) || content.length === 0) {
        errors.push(`toolResult ${callId} has no content[] to trim`);
        skipped++;
        targetsByCallId.delete(callId);
        continue;
      }
      const newText = q.replacement
        ? `${TRIM_SENTINEL} ${q.replacement}`
        : TRIM_SENTINEL;
      let touched = false;
      for (const c of content) {
        if (c?.type === 'text' && typeof c.text === 'string') {
          trimmedBytes += Buffer.byteLength(c.text, 'utf8') - Buffer.byteLength(newText, 'utf8');
          c.text = newText;
          touched = true;
        }
      }
      if (!touched) {
        errors.push(`toolResult ${callId} has no text blocks`);
        skipped++;
        targetsByCallId.delete(callId);
        continue;
      }
      lines[i] = JSON.stringify(obj);
      applied++;
      targetsByCallId.delete(callId);
      continue;
    }

    // (B) assistant message containing the dynamic-trim's own toolCall — self-compact
    if (role === 'assistant') {
      const content = obj.message?.content;
      if (!Array.isArray(content)) continue;
      let lineChanged = false;
      for (const c of content) {
        if (c?.type !== 'toolCall') continue;
        if (typeof c.id !== 'string') continue;
        const q = selfByCallId.get(c.id);
        if (!q) continue;
        // Replace the bulky arguments with the minimal self-compacted form.
        // Preserves toolCallId for traceability; _self_compacted flag for
        // tooling (future plexum dynamic-recall etc.) to recognise.
        c.arguments = { tool_call_id: q.targetCallId, _self_compacted: true };
        selfByCallId.delete(c.id);
        lineChanged = true;
        selfCompacted++;
      }
      if (lineChanged) {
        lines[i] = JSON.stringify(obj);
      }
    }
  }

  for (const callId of targetsByCallId.keys()) {
    errors.push(`toolResult ${callId} not found in session`);
    skipped++;
  }
  for (const selfId of selfByCallId.keys()) {
    errors.push(`self tool_use ${selfId} not found in session (cannot self-compact)`);
  }

  const tmp = `${sessionFile}.trim.${process.pid}.${Date.now()}`;
  await fs.promises.writeFile(tmp, lines.join('\n'), 'utf8');
  await fs.promises.rename(tmp, sessionFile);

  return {
    session_file: sessionFile,
    applied,
    skipped,
    trimmed_bytes: trimmedBytes,
    self_compacted: selfCompacted,
    errors,
  };
}

export function pendingTrimSessions(): string[] {
  return Array.from(trimQueue.keys());
}