/// <summary>
/// Caches a file from the web using the POST method.
/// </summary>
/// <param name="url">The url to request.</param>
/// <param name="cachePath">The path where the cached file will be saved.</param>
/// <param name="ttl">The amount of time before the cache expires.</param>
/// <param name="parameters">The POST parameters.</param>
/// <param name="action">A validation or processing action to be run after downloading the file but before copying it to <paramref name="cachePath"/>.</param>
public static CacheResult CacheFilePost(string url, string cachePath, TimeSpan ttl, IEnumerable<KeyValuePair<string, string>> parameters, PostDownloadAction action)
{
return CacheFileInternal(HttpMethod.Post, url, cachePath, new TtlCacheStrategy(ttl), parameters, action);
}
/// <summary>
/// Caches a file from the web using the GET method.
/// </summary>
/// <param name="url">The url to request.</param>
/// <param name="cachePath">The path where the cached file will be saved.</param>
/// <param name="ttl">The amount of time before the cache expires.</param>
/// <param name="action">A validation or processing action to be run after downloading the file but before copying it to <paramref name="cachePath"/>.</param>
public static CacheResult CacheFile(string url, string cachePath, TimeSpan ttl, PostDownloadAction action)
{
return CacheFileInternal(HttpMethod.Get, url, cachePath, new TtlCacheStrategy(ttl), null, action);
}
/// <summary>
/// Caches a file from the web using the GET method.
/// </summary>
/// <param name="url">The url to request.</param>
/// <param name="cachePath">The path where the cached file will be saved.</param>
/// <param name="cacheStrategy">decides file cache state and duration</param>
/// <param name="action">A validation or processing action to be run after downloading the file but before copying it to <paramref name="cachePath"/>.</param>
public static CacheResult CacheFile(string url, string cachePath, ICacheStrategy cacheStrategy, PostDownloadAction action)
{
return CacheFileInternal(HttpMethod.Get, url, cachePath, cacheStrategy, null, action);
}
/// <summary>
/// Caches a file from the internets.
/// </summary>
/// <param name="method">specifies GET or POST</param>
/// <param name="url">the url to request</param>
/// <param name="cachePath">the path where the cached file will be saved</param>
/// <param name="cacheStrategy">decides file cache state and duration</param>
/// <param name="parameters">parameters for POST requests</param>
/// <param name="action">a validation or processing action to be run after downloading the file but before copying it to <paramref name="cachePath"/></param>
private static CacheResult CacheFileInternal(HttpMethod method, string url, string cachePath, ICacheStrategy cacheStrategy, IEnumerable<KeyValuePair<string, string>> parameters, PostDownloadAction action)
{
CacheResult currentResult;
string tempPath = null;
// validate parameters
if (method == HttpMethod.Get && parameters != null)
throw new ArgumentException("GET method and parameters don't mix");
// check whether the file is cached
currentResult = IsFileCached(cachePath, cacheStrategy);
if (currentResult.State == CacheState.Cached)
return currentResult;
try
{
// download to a temp file
switch (method)
{
case HttpMethod.Get:
tempPath = DownloadUrlGet(url);
break;
case HttpMethod.Post:
tempPath = DownloadUrlPost(url, parameters);
break;
default:
throw new ArgumentException("Unknown HTTP method " + method.ToString());
}
// call the PostDownloadAction if there is one
if (action != null)
action(tempPath);
// we assume the file is fine if the PostDownloadAction didn't throw an exception
File.Copy(tempPath, cachePath, true);
// return success
return new CacheResult(cachePath, true, CacheState.Cached, cacheStrategy.GetCachedUntil(cachePath));
}
catch (Exception ex)
{
// if we currently have a valid local copy of the file, even if out of date, return that info
if (currentResult.State != CacheState.Uncached)
return CacheResult.FromExisting(currentResult, ex);
else
return CacheResult.Uncached(ex);
}
finally
{
// get rid of the temp file, don't care if it doesn't work
try { if (!string.IsNullOrEmpty(tempPath)) File.Delete(tempPath); }
catch { /* pass */ }
}
}
