# DbContext 工厂

> 所属模块：[数据库切换支持](./概览.md)

---

## 1. 接口定义

```csharp
// Data/IDbContextFactory.cs
using WCTDataMiner.Data;

namespace WCTDataMiner.Data;

public interface IDbContextFactory
{
    WctMinerDbContext CreateDbContext();
}
```

---

## 2. 工厂实现

```csharp
// Data/DbContextFactory.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace WCTDataMiner.Data;

public class DbContextFactory : IDbContextFactory
{
    private readonly IConfiguration _configuration;

    public DbContextFactory(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    public WctMinerDbContext CreateDbContext()
    {
        var dbType = _configuration["Database:Type"]?.ToLower() ?? "sqlite";
        var optionsBuilder = new DbContextOptionsBuilder<WctMinerDbContext>();

        switch (dbType)
        {
            case "postgresql":
            case "postgres":
                var pgConnStr = BuildPostgreSqlConnectionString();
                optionsBuilder.UseNpgsql(pgConnStr);
                break;
            
            case "sqlite":
            default:
                var dbPath = _configuration["Database:Path"] ?? "./data/database/wctminer.db";
                EnsureDirectoryExists(dbPath);
                optionsBuilder.UseSqlite($"Data Source={dbPath}");
                break;
        }

#if DEBUG
        optionsBuilder.EnableSensitiveDataLogging();
        optionsBuilder.EnableDetailedErrors();
#endif

        return new WctMinerDbContext(optionsBuilder.Options);
    }

    private string BuildPostgreSqlConnectionString()
    {
        var host = _configuration["Database:Host"] ?? "localhost";
        var port = _configuration["Database:Port"] ?? "5432";
        var name = _configuration["Database:Name"] ?? "wctminer";
        var user = _configuration["Database:User"] ?? "postgres";
        var password = _configuration["Database:Password"] ?? "";

        return $"Host={host};Port={port};Database={name};Username={user};Password={password}";
    }

    private static void EnsureDirectoryExists(string dbPath)
    {
        var directory = Path.GetDirectoryName(dbPath);
        if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
        {
            Directory.CreateDirectory(directory);
        }
    }
}
```

---

## 3. 依赖注入扩展

```csharp
// Extensions/ServiceCollectionExtensions.cs
using Microsoft.Extensions.DependencyInjection;
using WCTDataMiner.Data;

namespace WCTDataMiner.Extensions;

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddDatabaseServices(
        this IServiceCollection services, 
        IConfiguration configuration)
    {
        // 注册 DbContext 工厂
        services.AddScoped<IDbContextFactory, DbContextFactory>();
        
        // 注册 DbContext（通过工厂创建）
        services.AddScoped<WctMinerDbContext>(sp =>
        {
            var factory = sp.GetRequiredService<IDbContextFactory>();
            return factory.CreateDbContext();
        });

        return services;
    }
}
```