import { agentClientId, encodeAwareness } from "./room-awareness";

const AGENT_PRESENCE_MS = 30 * 1000;
const AGENT_COLOR = "#a371f7";

/** Agents are keyed by (user, name) so two people's "claude" don't overwrite each other's presence. */
export function agentKey(userId: string, agent: string): string {
  return `${userId}:${agent}`;
}

export type TextEdit = { from: number; to: number; insert: string };
export type ApplyResult =
  | { ok: true; version: number; text: string }
  | { ok: false; error: "stale" | string; version: number; text: string };
type AgentRow = { name: string; user_name: string; path: string | null; clock: number };

/** Records an agent's latest activity and returns the awareness update announcing its cursor. */
export function touchAgent(sql: SqlStorage, agent: string, user: string, path: string, cursor: number): Uint8Array {
  const row = sql.exec<{ clock: number }>("SELECT clock FROM agents WHERE name = ?", agent).toArray()[0];
  const clock = (row?.clock ?? 0) + 1;
  sql.exec(
    `INSERT INTO agents (name, user_name, path, clock, expires_at) VALUES (?, ?, ?, ?, ?)
     ON CONFLICT(name) DO UPDATE SET user_name = excluded.user_name, path = excluded.path, clock = excluded.clock, expires_at = excluded.expires_at`,
    agent,
    user,
    path,
    clock,
    Date.now() + AGENT_PRESENCE_MS,
  );
  return agentUpdate({ name: agent, user_name: user, path, clock, cursor });
}

export function liveAgents(sql: SqlStorage): AgentRow[] {
  return sql
    .exec<AgentRow>("SELECT name, user_name, path, clock FROM agents WHERE expires_at > ?", Date.now())
    .toArray();
}

export function expireAgents(sql: SqlStorage): Array<{ name: string; clock: number }> {
  const expired = sql
    .exec<{ name: string; clock: number }>("SELECT name, clock FROM agents WHERE expires_at <= ?", Date.now())
    .toArray();
  for (const agent of expired) sql.exec("DELETE FROM agents WHERE name = ?", agent.name);
  return expired;
}

export function removeAgent(sql: SqlStorage, agent: string): number | null {
  const row = sql.exec<{ clock: number }>("SELECT clock FROM agents WHERE name = ?", agent).toArray()[0];
  if (!row) return null;
  sql.exec("DELETE FROM agents WHERE name = ?", agent);
  return row.clock;
}

export function agentUpdate(agent: AgentRow & { cursor?: number }): Uint8Array {
  const display = agent.name.slice(agent.name.indexOf(":") + 1);
  const state = {
    user: {
      name: `${display} (agent for ${agent.user_name})`,
      id: `agent:${agent.name}`,
      kind: "agent",
      color: AGENT_COLOR,
    },
    path: agent.path,
    selections: agent.cursor === undefined ? [] : [{ anchor: agent.cursor, head: agent.cursor }],
  };
  return encodeAwareness([{ clientId: agentClientId(agent.name), clock: agent.clock, state }]);
}

/** Edits apply back to front so earlier offsets stay valid. */
export function sortEdits(edits: TextEdit[]): TextEdit[] {
  return [...edits].sort((left, right) => right.from - left.from);
}

export function checkEdits(sorted: TextEdit[], length: number, maxLength: number): string | null {
  let previousFrom = Number.POSITIVE_INFINITY;
  let next = length;
  for (const edit of sorted) {
    if (edit.from < 0 || edit.to < edit.from || edit.to > length) return "Edit range out of bounds";
    if (edit.to > previousFrom) return "Edits overlap";
    previousFrom = edit.from;
    next += edit.insert.length - (edit.to - edit.from);
  }
  return next > maxLength ? "File too large" : null;
}

export function editCursor(sorted: TextEdit[]): number {
  const first = sorted[sorted.length - 1];
  return first ? first.from + first.insert.length : 0;
}