import { existsSync } from 'node:fs';
import { homedir } from 'node:os';
import path from 'node:path';
import { prependPathEntry } from './env-path';

type EnvMap = Record<string, string | undefined>;

function dotnetExecutableName(): string {
  return process.platform === 'win32' ? 'dotnet.exe' : 'dotnet';
}

export function getDotnetPathCandidates(): string[] {
  if (process.platform === 'win32') {
    return [
      path.join(homedir(), '.dotnet'),
      path.join(process.env.ProgramFiles || 'C:\\Program Files', 'dotnet'),
      path.join(process.env['ProgramFiles(x86)'] || 'C:\\Program Files (x86)', 'dotnet'),
    ];
  }

  return [
    path.join(homedir(), '.dotnet'),
    '/usr/local/share/dotnet',
    '/opt/homebrew/bin',
    '/usr/local/bin',
  ];
}

export function resolveDotnetExecutable(): string | null {
  const executable = dotnetExecutableName();
  for (const dir of getDotnetPathCandidates()) {
    const candidate = path.join(dir, executable);
    if (existsSync(candidate)) return candidate;
  }
  return null;
}

export function buildDotnetEnv(baseEnv: EnvMap): EnvMap {
  let env: EnvMap = { ...baseEnv };
  const existingDirs = getDotnetPathCandidates().filter((entry) => existsSync(entry));
  for (const dir of existingDirs.slice().reverse()) {
    env = prependPathEntry(env, dir).env;
  }

  const userDotnet = path.join(homedir(), '.dotnet');
  if (existsSync(path.join(userDotnet, dotnetExecutableName()))) {
    env.DOTNET_ROOT = userDotnet;
  } else {
    const systemRoot = process.platform === 'darwin' ? '/usr/local/share/dotnet' : null;
    if (systemRoot && existsSync(path.join(systemRoot, dotnetExecutableName()))) {
      env.DOTNET_ROOT = systemRoot;
    }
  }

  return env;
}