123 lines
4.0 KiB
C#
123 lines
4.0 KiB
C#
using Microsoft.AspNetCore.Mvc;
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using System;
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using System.IO;
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using System.Net;
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using System.Net.Http;
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using System.Net.Http.Headers;
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using System.Text.Json;
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using System.Threading.Tasks;
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using Microsoft.Extensions.Caching.Memory;
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var builder = WebApplication.CreateBuilder(args);
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// Add services to the container.
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builder.Services.AddHttpClient();
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builder.Services.AddMemoryCache();
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var app = builder.Build();
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// Configure the HTTP request pipeline.
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string cachePath = Environment.GetEnvironmentVariable("CACHE_PATH") ?? "cache";
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if (!Directory.Exists(cachePath))
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{
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Directory.CreateDirectory(cachePath);
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}
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app.MapGet("/{url}", async (string url, IHttpClientFactory clientFactory, IMemoryCache memoryCache) =>
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{
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var client = clientFactory.CreateClient();
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string encodedUrl = WebUtility.UrlEncode(url);
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string filePath = Path.Combine(cachePath, encodedUrl);
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string metadataPath = Path.Combine(cachePath, $"{encodedUrl}.json");
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if (memoryCache.TryGetValue(encodedUrl, out FileMetadata? mdFromCache) && DateTime.Now <= mdFromCache?.Expiry)
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{
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return Results.File(filePath, mdFromCache.ContentType ?? "application/octet-stream");
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}
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if (File.Exists(filePath) && File.Exists(metadataPath))
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{
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var metadata = JsonSerializer.Deserialize<FileMetadata>(await File.ReadAllTextAsync(metadataPath)) ?? new FileMetadata();
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var request = new HttpRequestMessage(HttpMethod.Get, url);
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if (!string.IsNullOrEmpty(metadata.ETag))
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{
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request.Headers.IfNoneMatch.Add(EntityTagHeaderValue.Parse(metadata.ETag));
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}
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var response = await client.SendAsync(request);
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if (response.StatusCode == HttpStatusCode.NotModified)
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{
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metadata.CachedAt = DateTime.Now;
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metadata.Expiry = DateTime.Now.AddHours(24);
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await WriteMetadataAsync(metadataPath, metadata, memoryCache, encodedUrl);
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return Results.File(filePath, metadata.ContentType ?? "application/octet-stream");
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}
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else if (response.IsSuccessStatusCode)
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{
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return await SaveAndReturnFile(response, filePath, metadataPath, memoryCache, encodedUrl, url);
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}
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}
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try
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{
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var response = await client.GetAsync(url);
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if (!response.IsSuccessStatusCode)
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{
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return Results.StatusCode((int)response.StatusCode);
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}
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return await SaveAndReturnFile(response, filePath, metadataPath, memoryCache, encodedUrl, url);
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}
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catch (Exception ex)
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{
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return Results.Problem(ex.Message, statusCode: 500);
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}
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});
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app.Run();
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/// <summary>
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/// Saves the response content to disk and updates the metadata.
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/// </summary>
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async Task<IResult> SaveAndReturnFile(HttpResponseMessage response, string filePath, string metadataPath, IMemoryCache memoryCache, string encodedUrl, string url)
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{
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var content = await response.Content.ReadAsByteArrayAsync();
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var contentType = response.Content.Headers.ContentType?.ToString() ?? "application/octet-stream";
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var eTag = response.Headers.ETag?.ToString();
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await File.WriteAllBytesAsync(filePath, content);
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var metadata = new FileMetadata
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{
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Url = url,
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ContentType = contentType,
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CachedAt = DateTime.Now,
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Expiry = DateTime.Now.AddHours(24),
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ETag = eTag
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};
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await WriteMetadataAsync(metadataPath, metadata, memoryCache, encodedUrl);
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return Results.File(filePath, contentType);
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}
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/// <summary>
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/// Writes metadata to disk and caches it in memory.
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/// </summary>
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async Task WriteMetadataAsync(string metadataPath, FileMetadata metadata, IMemoryCache memoryCache, string cacheKey)
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{
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await File.WriteAllTextAsync(metadataPath, JsonSerializer.Serialize(metadata));
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memoryCache.Set(cacheKey, metadata, TimeSpan.FromMinutes(15));
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}
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public class FileMetadata
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{
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public string Url { get; set; } = string.Empty;
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public string? ContentType { get; set; }
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public DateTime CachedAt { get; set; }
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public DateTime Expiry { get; set; }
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public string? ETag { get; set; }
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}
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