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/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: VNLib
* Package: Emails.Transactional
* File: EmailTemplateStore.cs
*
* EmailTemplateStore.cs is part of Emails.Transactional which is part of the larger
* VNLib collection of libraries and utilities.
*
* Emails.Transactional is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published
* by the Free Software Foundation, either version 2 of the License,
* or (at your option) any later version.
*
* Emails.Transactional is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Emails.Transactional. If not, see http://www.gnu.org/licenses/.
*/
using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;
using Fluid;
using VNLib.Utils.IO;
using VNLib.Utils.Extensions;
using VNLib.Utils.Memory.Caching;
using VNLib.Plugins;
using VNLib.Plugins.Extensions.Loading;
using VNLib.Plugins.Extensions.Data.Storage;
using Emails.Transactional.Mta;
namespace Emails.Transactional.Templates
{
[ConfigurationName("templates")]
internal sealed class EmailTemplateStore : ITemplateStorage
{
private readonly FluidParser _parser;
private readonly Dictionary<string, EmailTemplate> _templateCache;
private readonly ISimpleFilesystem _filesystem;
private readonly TimeSpan _cacheValidFor;
public EmailTemplateStore(PluginBase plugin, IConfigScope config)
{
_parser = new();
_templateCache = new(StringComparer.OrdinalIgnoreCase);
_cacheValidFor = config["cache_valid_for_sec"].GetTimeSpan(TimeParseType.Seconds);
string fsPath = config.GetRequiredProperty("template_path", e => e.GetString()!);
//Get the filesystem
ISimpleFilesystem baseFs = plugin.GetOrCreateSingleton<MinioStorage>();
//Create a new scope for the base path
_filesystem = baseFs.CreateNewScope(fsPath);
}
public Task<IEmailTemplate> GetTemplateAsync(string templateId, CancellationToken cancellation)
{
//try to get the template from the cache
if (_templateCache.TryGetOrEvictRecord(templateId, out EmailTemplate? template) > 0)
{
return Task.FromResult<IEmailTemplate>(template!);
}
//Load the template from the store
return GetTemplateFromStoreAsync(templateId, cancellation);
}
private async Task<IEmailTemplate> GetTemplateFromStoreAsync(string templateId, CancellationToken cancellation)
{
//memory stream for template data
using VnMemoryStream templateData = new();
//remove leading slash
if (templateId.StartsWith('/'))
{
templateId = templateId[1..];
}
//Recover template data
long read = await _filesystem.ReadFileAsync(templateId, templateData, cancellation);
if(read <= 0)
{
throw new TemplateLookupFailedException($"Template {templateId} not found");
}
//Rewind the stream
templateData.Seek(0, SeekOrigin.Begin);
//To string
string templateString = Encoding.UTF8.GetString(templateData.AsSpan());
//Try to parse the template and raise exception if it fails
if (!_parser.TryParse(templateString, out IFluidTemplate template, out string error))
{
throw new TemplateLookupFailedException($"A template parse error occured: {error}");
}
//Create new email template
EmailTemplate et = new(template);
//Store template in cache
_templateCache.StoreRecord(templateId, et, _cacheValidFor);
return et;
}
private sealed record class EmailTemplate(IFluidTemplate Template) : IEmailTemplate, ICacheable
{
///<inheritdoc/>
public DateTime Expires { get; set; }
///<inheritdoc/>
public bool Equals(ICacheable? other) => ReferenceEquals(this, other);
///<inheritdoc/>
public void Evicted()
{ }
///<inheritdoc/>
public IEmailMessageData RenderTemplate(object variables)
{
//Create a template model
TemplateContext ctx = new(variables);
string html = Template.Render(ctx);
return new EmailMessageData(html);
}
private sealed record class EmailMessageData(string Rendered) : IEmailMessageData
{
public string GetHtml() => Rendered;
}
}
}
}
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