import crypto from "node:crypto";
import path from "node:path";

import { loadConfig } from "../config/config.js";
import {
  loadSessionStore,
  resolveAgentIdFromSessionKey,
  resolveStorePath,
} from "../config/sessions.js";
import { callGateway } from "../gateway/call.js";
import { readLatestAssistantReply } from "./tools/agent-step.js";

function formatDurationShort(valueMs?: number) {
  if (!valueMs || !Number.isFinite(valueMs) || valueMs <= 0) return undefined;
  const totalSeconds = Math.round(valueMs / 1000);
  const hours = Math.floor(totalSeconds / 3600);
  const minutes = Math.floor((totalSeconds % 3600) / 60);
  const seconds = totalSeconds % 60;
  if (hours > 0) return `${hours}h${minutes}m`;
  if (minutes > 0) return `${minutes}m${seconds}s`;
  return `${seconds}s`;
}

function formatTokenCount(value?: number) {
  if (!value || !Number.isFinite(value)) return "0";
  if (value >= 1_000_000) return `${(value / 1_000_000).toFixed(1)}m`;
  if (value >= 1_000) return `${(value / 1_000).toFixed(1)}k`;
  return String(Math.round(value));
}

function formatUsd(value?: number) {
  if (value === undefined || !Number.isFinite(value)) return undefined;
  if (value >= 1) return `$${value.toFixed(2)}`;
  if (value >= 0.01) return `$${value.toFixed(2)}`;
  return `$${value.toFixed(4)}`;
}

function resolveModelCost(params: {
  provider?: string;
  model?: string;
  config: ReturnType<typeof loadConfig>;
}):
  | {
      input: number;
      output: number;
      cacheRead: number;
      cacheWrite: number;
    }
  | undefined {
  const provider = params.provider?.trim();
  const model = params.model?.trim();
  if (!provider || !model) return undefined;
  const models = params.config.models?.providers?.[provider]?.models ?? [];
  const entry = models.find((candidate) => candidate.id === model);
  return entry?.cost;
}

async function waitForSessionUsage(params: { sessionKey: string }) {
  const cfg = loadConfig();
  const agentId = resolveAgentIdFromSessionKey(params.sessionKey);
  const storePath = resolveStorePath(cfg.session?.store, { agentId });
  let entry = loadSessionStore(storePath)[params.sessionKey];
  if (!entry) return { entry, storePath };
  const hasTokens = () =>
    entry &&
    (typeof entry.totalTokens === "number" ||
      typeof entry.inputTokens === "number" ||
      typeof entry.outputTokens === "number");
  if (hasTokens()) return { entry, storePath };
  for (let attempt = 0; attempt < 4; attempt += 1) {
    await new Promise((resolve) => setTimeout(resolve, 200));
    entry = loadSessionStore(storePath)[params.sessionKey];
    if (hasTokens()) break;
  }
  return { entry, storePath };
}

async function buildSubagentStatsLine(params: {
  sessionKey: string;
  startedAt?: number;
  endedAt?: number;
}) {
  const cfg = loadConfig();
  const { entry, storePath } = await waitForSessionUsage({
    sessionKey: params.sessionKey,
  });

  const sessionId = entry?.sessionId;
  const transcriptPath =
    sessionId && storePath ? path.join(path.dirname(storePath), `${sessionId}.jsonl`) : undefined;

  const input = entry?.inputTokens;
  const output = entry?.outputTokens;
  const total =
    entry?.totalTokens ??
    (typeof input === "number" && typeof output === "number" ? input + output : undefined);
  const runtimeMs =
    typeof params.startedAt === "number" && typeof params.endedAt === "number"
      ? Math.max(0, params.endedAt - params.startedAt)
      : undefined;

  const provider = entry?.modelProvider;
  const model = entry?.model;
  const costConfig = resolveModelCost({ provider, model, config: cfg });
  const cost =
    costConfig && typeof input === "number" && typeof output === "number"
      ? (input * costConfig.input + output * costConfig.output) / 1_000_000
      : undefined;

  const parts: string[] = [];
  const runtime = formatDurationShort(runtimeMs);
  parts.push(`runtime ${runtime ?? "n/a"}`);
  if (typeof total === "number") {
    const inputText = typeof input === "number" ? formatTokenCount(input) : "n/a";
    const outputText = typeof output === "number" ? formatTokenCount(output) : "n/a";
    const totalText = formatTokenCount(total);
    parts.push(`tokens ${totalText} (in ${inputText} / out ${outputText})`);
  } else {
    parts.push("tokens n/a");
  }
  const costText = formatUsd(cost);
  if (costText) parts.push(`est ${costText}`);
  parts.push(`sessionKey ${params.sessionKey}`);
  if (sessionId) parts.push(`sessionId ${sessionId}`);
  if (transcriptPath) parts.push(`transcript ${transcriptPath}`);

  return `Stats: ${parts.join(" \u2022 ")}`;
}

export function buildSubagentSystemPrompt(params: {
  requesterSessionKey?: string;
  requesterChannel?: string;
  childSessionKey: string;
  label?: string;
  task?: string;
}) {
  const taskText =
    typeof params.task === "string" && params.task.trim()
      ? params.task.replace(/\s+/g, " ").trim()
      : "{{TASK_DESCRIPTION}}";
  const lines = [
    "# Subagent Context",
    "",
    "You are a **subagent** spawned by the main agent for a specific task.",
    "",
    "## Your Role",
    `- You were created to handle: ${taskText}`,
    "- Complete this task. That's your entire purpose.",
    "- You are NOT the main agent. Don't try to be.",
    "",
    "## Rules",
    "1. **Stay focused** - Do your assigned task, nothing else",
    "2. **Complete the task** - Your final message will be automatically reported to the main agent",
    "3. **Don't initiate** - No heartbeats, no proactive actions, no side quests",
    "4. **Be ephemeral** - You may be terminated after task completion. That's fine.",
    "",
    "## Output Format",
    "When complete, your final response should include:",
    "- What you accomplished or found",
    "- Any relevant details the main agent should know",
    "- Keep it concise but informative",
    "",
    "## What You DON'T Do",
    "- NO user conversations (that's main agent's job)",
    "- NO external messages (email, tweets, etc.) unless explicitly tasked",
    "- NO cron jobs or persistent state",
    "- NO pretending to be the main agent",
    "- NO using the `message` tool directly",
    "",
    "## Session Context",
    params.label ? `- Label: ${params.label}` : undefined,
    params.requesterSessionKey ? `- Requester session: ${params.requesterSessionKey}.` : undefined,
    params.requesterChannel ? `- Requester channel: ${params.requesterChannel}.` : undefined,
    `- Your session: ${params.childSessionKey}.`,
    "",
  ].filter((line): line is string => line !== undefined);
  return lines.join("\n");
}

export type SubagentRunOutcome = {
  status: "ok" | "error" | "timeout" | "unknown";
  error?: string;
};

export async function runSubagentAnnounceFlow(params: {
  childSessionKey: string;
  childRunId: string;
  requesterSessionKey: string;
  requesterChannel?: string;
  requesterDisplayKey: string;
  task: string;
  timeoutMs: number;
  cleanup: "delete" | "keep";
  roundOneReply?: string;
  waitForCompletion?: boolean;
  startedAt?: number;
  endedAt?: number;
  label?: string;
  outcome?: SubagentRunOutcome;
}): Promise<boolean> {
  let didAnnounce = false;
  try {
    let reply = params.roundOneReply;
    let outcome: SubagentRunOutcome | undefined = params.outcome;
    if (!reply && params.waitForCompletion !== false) {
      const waitMs = Math.min(params.timeoutMs, 60_000);
      const wait = (await callGateway({
        method: "agent.wait",
        params: {
          runId: params.childRunId,
          timeoutMs: waitMs,
        },
        timeoutMs: waitMs + 2000,
      })) as {
        status?: string;
        error?: string;
        startedAt?: number;
        endedAt?: number;
      };
      if (wait?.status === "timeout") {
        outcome = { status: "timeout" };
      } else if (wait?.status === "error") {
        outcome = { status: "error", error: wait.error };
      } else if (wait?.status === "ok") {
        outcome = { status: "ok" };
      }
      if (typeof wait?.startedAt === "number" && !params.startedAt) {
        params.startedAt = wait.startedAt;
      }
      if (typeof wait?.endedAt === "number" && !params.endedAt) {
        params.endedAt = wait.endedAt;
      }
      if (wait?.status === "timeout") {
        if (!outcome) outcome = { status: "timeout" };
      }
      reply = await readLatestAssistantReply({
        sessionKey: params.childSessionKey,
      });
    }

    if (!reply) {
      reply = await readLatestAssistantReply({
        sessionKey: params.childSessionKey,
      });
    }

    if (!outcome) outcome = { status: "unknown" };

    // Build stats
    const statsLine = await buildSubagentStatsLine({
      sessionKey: params.childSessionKey,
      startedAt: params.startedAt,
      endedAt: params.endedAt,
    });

    // Build status label
    const statusLabel =
      outcome.status === "ok"
        ? "completed successfully"
        : outcome.status === "timeout"
          ? "timed out"
          : outcome.status === "error"
            ? `failed: ${outcome.error || "unknown error"}`
            : "finished with unknown status";

    // Build instructional message for main agent
    const taskLabel = params.label || params.task || "background task";
    const triggerMessage = [
      `A background task "${taskLabel}" just ${statusLabel}.`,
      "",
      "Findings:",
      reply || "(no output)",
      "",
      statsLine,
      "",
      "Summarize this naturally for the user. Keep it brief (1-2 sentences). Flow it into the conversation naturally.",
      "Do not mention technical details like tokens, stats, or that this was a background task.",
      "You can respond with NO_REPLY if no announcement is needed (e.g., internal task with no user-facing result).",
    ].join("\n");

    // Send to main agent - it will respond in its own voice
    await callGateway({
      method: "agent",
      params: {
        sessionKey: params.requesterSessionKey,
        message: triggerMessage,
        deliver: true,
        idempotencyKey: crypto.randomUUID(),
      },
      timeoutMs: 60_000,
    });

    didAnnounce = true;
  } catch {
    // Best-effort follow-ups; ignore failures to avoid breaking the caller response.
  } finally {
    // Patch label after all writes complete
    if (params.label) {
      try {
        await callGateway({
          method: "sessions.patch",
          params: { key: params.childSessionKey, label: params.label },
          timeoutMs: 10_000,
        });
      } catch {
        // Best-effort
      }
    }
    if (params.cleanup === "delete") {
      try {
        await callGateway({
          method: "sessions.delete",
          params: { key: params.childSessionKey, deleteTranscript: true },
          timeoutMs: 10_000,
        });
      } catch {
        // ignore
      }
    }
  }
  return didAnnounce;
}