klod68/gen-in-memory-demo-service

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name: gen-in-memory-demo-service description: "Use when you need a fake or stub implementation of a service for demos, local development, or testing without a real backend. Generates an in-memory class that implements the real service interface, with seed data, realistic delays, and DI registration that can be swapped. Also invoke when the user mentions: fake service, in-memory stub, demo service, mock service for dev, test double. Domain: Code Generation, Testing. Level: Intermediate."

Generate an in-memory demo service implementing I${1:EntityName}Service.

Context

• Entity name: ${1:EntityName}
• Namespace root: ${2:MyApp}
• Entity properties: ${3:e.g. int Id, string Name, string Category, bool IsActive}
• Create parameters: ${4:e.g. string name, string category}
• Update parameters: ${5:e.g. int id, string name}
• Filterable criteria properties: ${6:e.g. string? nameSearch, string? category}
• Seed data (3–5 items): ${7:e.g. (1, "Alpha Widget", "Tools"), (2, "Beta Gadget", "Devices")}

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Required output — generate ALL of the following:

1. In-memory service class

${2}.Infrastructure.Demo.InMemory${1}Service.cs

/// <summary>
/// In-memory simulation of <see cref="I${1}Service"/> for demos and offline development.
/// Mirrors the real service contract including validation, delays, and error behavior.
/// </summary>
public sealed class InMemory${1}Service : I${1}Service
{
    private readonly List<${1}> _items = [];
    private readonly List<string> _operationLog = [];
    private readonly ILogger<InMemory${1}Service> _logger;
    private int _nextId = 1;

    public InMemory${1}Service(ILogger<InMemory${1}Service> logger) { ... }

    // ── Commands ──────────────────────────────────────────────────────────
    // ── Queries ───────────────────────────────────────────────────────────
    // ── Observability ─────────────────────────────────────────────────────
    // ── Helpers ───────────────────────────────────────────────────────────
}

Key requirements per section:

Commands — match real service validation exactly:

• Guard clauses identical to what the real implementation would enforce
• await Task.Delay(100–200, ct).ConfigureAwait(false) to simulate latency
• Log the equivalent stored procedure or API call: "INSERT → usp_Insert${1} @Param=value → NewId=N"
• Return the new ID, affected-row count, or bool per the interface contract

Queries — simulate reads:

• await Task.Delay(50–80, ct).ConfigureAwait(false)
• Apply criteria filters with if (criteria.X is not null) query = query.Where(...) pattern
• Log the equivalent query with row count

Observability (public — for demo UI use):

• IReadOnlyList<string> GetOperationLog() — returns log as read-only
• void ClearLog() — clears the log

Helpers (private):

• void Log(string entry) — prepends [HH:mm:ss.fff] timestamp
• void SeedSampleData() — populates _items from context above, then calls _operationLog.Clear()

2. DI registration comment

Show both registrations as a code comment:

// Development / demo:
builder.Services.AddScoped<I${1}Service, InMemory${1}Service>();

// Production:
builder.Services.AddScoped<I${1}Service, ${1}Service>();

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Rules

• Same interface as the real service — no additional methods on the class (only the observability helpers)
• Same guard clauses and validation as the real implementation — demo callers get the same errors
• ConfigureAwait(false) on all awaits
• Seed data log is cleared after seeding — operation log shows only consumer actions
• Log entries document the equivalent real call, not the in-memory behavior
• internal sealed visibility — exposed via DI only

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Constraints

• Follow all rules in the workspace root instruction file
• No real database, HTTP, or file I/O — pure in-memory only
• Thread-safety is not required (demo use is single-user and single-threaded)
• Do not add any method not present on I${1}Service (except the two observability helpers)