import fs from "node:fs/promises";
import { resolveLaunchAgentPlistPath } from "./launchd.js";
import { resolveSystemdUserUnitPath } from "./systemd.js";

export type GatewayServiceCommand = {
  programArguments: string[];
  workingDirectory?: string;
  environment?: Record<string, string>;
  sourcePath?: string;
} | null;

export type ServiceConfigIssue = {
  code: string;
  message: string;
  detail?: string;
  level?: "recommended" | "aggressive";
};

export type ServiceConfigAudit = {
  ok: boolean;
  issues: ServiceConfigIssue[];
};

function hasGatewaySubcommand(programArguments?: string[]): boolean {
  return Boolean(programArguments?.some((arg) => arg === "gateway"));
}

function parseSystemdUnit(content: string): {
  after: Set<string>;
  wants: Set<string>;
  restartSec?: string;
} {
  const after = new Set<string>();
  const wants = new Set<string>();
  let restartSec: string | undefined;

  for (const rawLine of content.split(/\r?\n/)) {
    const line = rawLine.trim();
    if (!line) continue;
    if (line.startsWith("#") || line.startsWith(";")) continue;
    if (line.startsWith("[")) continue;
    const idx = line.indexOf("=");
    if (idx <= 0) continue;
    const key = line.slice(0, idx).trim();
    const value = line.slice(idx + 1).trim();
    if (!value) continue;
    if (key === "After") {
      for (const entry of value.split(/\s+/)) {
        if (entry) after.add(entry);
      }
    } else if (key === "Wants") {
      for (const entry of value.split(/\s+/)) {
        if (entry) wants.add(entry);
      }
    } else if (key === "RestartSec") {
      restartSec = value;
    }
  }

  return { after, wants, restartSec };
}

function isRestartSecPreferred(value: string | undefined): boolean {
  if (!value) return false;
  const parsed = Number.parseFloat(value);
  if (!Number.isFinite(parsed)) return false;
  return Math.abs(parsed - 5) < 0.01;
}

async function auditSystemdUnit(
  env: Record<string, string | undefined>,
  issues: ServiceConfigIssue[],
) {
  const unitPath = resolveSystemdUserUnitPath(env);
  let content = "";
  try {
    content = await fs.readFile(unitPath, "utf8");
  } catch {
    return;
  }

  const parsed = parseSystemdUnit(content);
  if (!parsed.after.has("network-online.target")) {
    issues.push({
      code: "systemd-after-network-online",
      message: "Missing systemd After=network-online.target",
      detail: unitPath,
      level: "recommended",
    });
  }
  if (!parsed.wants.has("network-online.target")) {
    issues.push({
      code: "systemd-wants-network-online",
      message: "Missing systemd Wants=network-online.target",
      detail: unitPath,
      level: "recommended",
    });
  }
  if (!isRestartSecPreferred(parsed.restartSec)) {
    issues.push({
      code: "systemd-restart-sec",
      message: "RestartSec does not match the recommended 5s",
      detail: unitPath,
      level: "recommended",
    });
  }
}

async function auditLaunchdPlist(
  env: Record<string, string | undefined>,
  issues: ServiceConfigIssue[],
) {
  const plistPath = resolveLaunchAgentPlistPath(env);
  let content = "";
  try {
    content = await fs.readFile(plistPath, "utf8");
  } catch {
    return;
  }

  const hasRunAtLoad = /<key>RunAtLoad<\/key>\s*<true\s*\/>/i.test(content);
  const hasKeepAlive = /<key>KeepAlive<\/key>\s*<true\s*\/>/i.test(content);
  if (!hasRunAtLoad) {
    issues.push({
      code: "launchd-run-at-load",
      message: "LaunchAgent is missing RunAtLoad=true",
      detail: plistPath,
      level: "recommended",
    });
  }
  if (!hasKeepAlive) {
    issues.push({
      code: "launchd-keep-alive",
      message: "LaunchAgent is missing KeepAlive=true",
      detail: plistPath,
      level: "recommended",
    });
  }
}

function auditGatewayCommand(
  programArguments: string[] | undefined,
  issues: ServiceConfigIssue[],
) {
  if (!programArguments || programArguments.length === 0) return;
  if (!hasGatewaySubcommand(programArguments)) {
    issues.push({
      code: "gateway-command-missing",
      message: "Service command does not include the gateway subcommand",
      level: "aggressive",
    });
  }
}

export async function auditGatewayServiceConfig(params: {
  env: Record<string, string | undefined>;
  command: GatewayServiceCommand;
  platform?: NodeJS.Platform;
}): Promise<ServiceConfigAudit> {
  const issues: ServiceConfigIssue[] = [];
  const platform = params.platform ?? process.platform;

  auditGatewayCommand(params.command?.programArguments, issues);

  if (platform === "linux") {
    await auditSystemdUnit(params.env, issues);
  } else if (platform === "darwin") {
    await auditLaunchdPlist(params.env, issues);
  }

  return { ok: issues.length === 0, issues };
}