import { execFileSync } from "node:child_process";
import type { AgentId } from "../external.ts";
import { log } from "../utils/cli.ts";
import type { ResolvedInstructions } from "../utils/instructions.ts";
import type { ResolvedPayload } from "../utils/payload.ts";
import type { TodoTracker } from "../utils/todoTracking.ts";

// maximum number of stderr lines to keep in the rolling buffer during agent execution
export const MAX_STDERR_LINES = 20;

// ── post-run commit enforcement ─────────────────────────────────────────────────

export const MAX_COMMIT_RETRIES = 3;

export function getGitStatus(): string {
  try {
    return execFileSync("git", ["status", "--porcelain"], {
      encoding: "utf-8",
      timeout: 10_000,
    }).trim();
  } catch {
    return "";
  }
}

export function buildCommitPrompt(_agentId: AgentId, status: string): string {
  return [
    `UNCOMMITTED CHANGES — the working tree is dirty. push all changes to a pull request (new or existing). \`git status\` must be clean before you finish.`,
    "",
    "```",
    status,
    "```",
  ].join("\n");
}

/**
 * token/cost usage data from a single agent run.
 *
 * NOTE on semantics: `inputTokens` here is the *total* billable input for the
 * run — non-cached input + cache read + cache write — matching the per-agent
 * SDK conventions. This is what gets persisted to `WorkflowRun.inputTokens`.
 *
 * The stdout token table and markdown step summary display a different "Input"
 * column that shows only the non-cached portion (derivable as
 * `inputTokens - cacheReadTokens - cacheWriteTokens`) so humans can see the
 * cache hit ratio at a glance. Dashboards that query `WorkflowRun.inputTokens`
 * directly are seeing the full total, not the log column.
 */
export interface AgentUsage {
  agent: string;
  /** full billable input: non-cached + cache read + cache write */
  inputTokens: number;
  outputTokens: number;
  cacheReadTokens?: number | undefined;
  cacheWriteTokens?: number | undefined;
  costUsd?: number | undefined;
}

export interface AgentToolUseEvent {
  toolName: string;
  input: unknown;
}

/**
 * Result returned by agent execution
 */
export interface AgentResult {
  success: boolean;
  output?: string | undefined;
  error?: string | undefined;
  metadata?: Record<string, unknown>;
  usage?: AgentUsage | undefined;
}

/**
 * Minimal context passed to agent.run()
 */
export interface AgentRunContext {
  payload: ResolvedPayload;
  resolvedModel?: string | undefined;
  mcpServerUrl: string;
  tmpdir: string;
  instructions: ResolvedInstructions;
  todoTracker?: TodoTracker | undefined;
  /**
   * called synchronously when the agent subprocess is killed for inner
   * activity timeout. lets main.ts tear down shared resources (MCP HTTP
   * server) so lingering SSE reconnects don't keep the outer timer alive.
   */
  onActivityTimeout?: (() => void) | undefined;
  onToolUse?: ((event: AgentToolUseEvent) => void) | undefined;
}

export interface Agent {
  name: AgentId;
  install: (token?: string) => Promise<string>;
  run: (ctx: AgentRunContext) => Promise<AgentResult>;
}

export const agent = (input: Agent): Agent => {
  return {
    ...input,
    run: async (ctx: AgentRunContext): Promise<AgentResult> => {
      log.debug(`» payload: ${JSON.stringify(ctx.payload, null, 2)}`);
      return input.run(ctx);
    },
  };
};

/** format a USD cost to 4 decimal places, always showing the leading zero */
export function formatCostUsd(costUsd: number): string {
  return costUsd.toFixed(4);
}

/**
 * merge two AgentUsage snapshots into one running total.
 *
 * both agent harnesses invoke their runner multiple times per `run()` when the
 * post-run dirty-tree loop kicks in (MAX_COMMIT_RETRIES). each invocation
 * produces its own AgentUsage; we sum them so downstream callers (usage
 * summary, WorkflowRun persistence) see the whole session — not just the
 * final retry's slice.
 *
 * returns `undefined` when both sides are empty so callers can short-circuit
 * without a special case. zero-valued cache / cost fields are dropped to
 * `undefined` for symmetry with each harness's `buildUsage`.
 */
export function mergeAgentUsage(
  a: AgentUsage | undefined,
  b: AgentUsage | undefined
): AgentUsage | undefined {
  // always return a fresh object — callers treat AgentUsage as immutable, and
  // returning `a` / `b` directly would leak that invariant to future callers
  if (!a && !b) return undefined;
  if (!a) return { ...(b as AgentUsage) };
  if (!b) return { ...a };
  const cacheRead = (a.cacheReadTokens ?? 0) + (b.cacheReadTokens ?? 0);
  const cacheWrite = (a.cacheWriteTokens ?? 0) + (b.cacheWriteTokens ?? 0);
  const cost = (a.costUsd ?? 0) + (b.costUsd ?? 0);
  return {
    agent: a.agent,
    inputTokens: a.inputTokens + b.inputTokens,
    outputTokens: a.outputTokens + b.outputTokens,
    cacheReadTokens: cacheRead > 0 ? cacheRead : undefined,
    cacheWriteTokens: cacheWrite > 0 ? cacheWrite : undefined,
    costUsd: cost > 0 ? cost : undefined,
  };
}

/**
 * unified per-run token table used by every agent harness.
 *
 * columns are kept stable across agents and models so downstream log parsers
 * (scripts/token-usage.ts, cost dashboards) only have to understand one format:
 *
 *   Input       non-cached input tokens sent this run
 *   Cache Read  input tokens served from prompt cache (Anthropic, etc.)
 *   Cache Write input tokens written to prompt cache this run
 *   Output      assistant output tokens
 *   Total       sum of the four columns — the real billable quantity
 *   Cost ($)    USD cost reported by the provider (only rendered when known)
 *
 * models that don't report prompt caching leave Cache Read / Write at 0.
 * OpenCode emits per-step `part.cost` sourced from models.dev (works across
 * Anthropic, OpenAI, Google, xAI, DeepSeek, Moonshot, OpenRouter, etc.);
 * Claude CLI emits `total_cost_usd` on its final `result` event. pass the
 * accumulated value via `costUsd` to render the Cost column.
 */
export function logTokenTable(t: {
  input: number;
  cacheRead: number;
  cacheWrite: number;
  output: number;
  costUsd?: number | undefined;
}): void {
  const total = t.input + t.cacheRead + t.cacheWrite + t.output;
  // narrow costUsd to a concrete number so the render path doesn't need a cast
  const costUsd = typeof t.costUsd === "number" && t.costUsd > 0 ? t.costUsd : undefined;

  const headerRow: Array<{ data: string; header: true }> = [
    { data: "Input", header: true },
    { data: "Cache Read", header: true },
    { data: "Cache Write", header: true },
    { data: "Output", header: true },
    { data: "Total", header: true },
  ];
  const dataRow: string[] = [
    String(t.input),
    String(t.cacheRead),
    String(t.cacheWrite),
    String(t.output),
    String(total),
  ];

  if (costUsd !== undefined) {
    headerRow.push({ data: "Cost ($)", header: true });
    dataRow.push(formatCostUsd(costUsd));
  }

  log.table([headerRow, dataRow]);
}