Switch to using effectful

.claude-plugin/marketplace.json

@@ -0,0 +1,13 @@
+{
+  "name": "domaindriven",
+  "owner": {
+    "name": "Tommy Engström"
+  },
+  "plugins": [
+    {
+      "name": "domaindriven",
+      "source": ".",
+      "description": "Claude skill for the domaindriven Haskell event sourcing and CQRS library"
+    }
+  ]
+}

.claude-plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "name": "domaindriven",
+  "description": "Claude skill for the domaindriven Haskell event sourcing and CQRS library",
+  "version": "0.1.0",
+  "author": {
+    "name": "Tommy Engström"
+  },
+  "repository": "https://github.com/tommyengstrom/domaindriven",
+  "license": "BSD-3-Clause",
+  "keywords": ["haskell", "event-sourcing", "cqrs", "domain-driven-design", "effectful", "servant"]
+}

.claude/settings.json

@@ -0,0 +1,13 @@
+{
+  "hooks": {
+    "Stop": [
+      {
+        "matcher": "",
+        "hooks": [
+        ]
+      }
+
+    ],
+    "PostToolUse": [ ]
+  }
+}

.claude/settings.local.json

@@ -0,0 +1,12 @@
+{
+  "permissions": {
+    "allow": [
+      "WebFetch(domain:hackage.haskell.org)",
+      "WebFetch(domain:hackage-content.haskell.org)",
+      "WebFetch(domain:github.com)",
+      "WebFetch(domain:www.stackage.org)",
+      "Bash(cabal:*)"
+    ],
+    "deny": []
+  }
+}

.github/workflows/main.yaml

@@ -2,20 +2,13 @@ name: Run tests
 
 on:
   push:
-    branches: [master]
-  pull_request:
-    branches: ['*']
 
 jobs:
   test:
     runs-on: ubuntu-latest
 
-    env:
-      COMPOSE_DOCKER_CLI_BUILD: 1
-      DOCKER_BUILDKIT: 1
-
     services:
-      claims-db:
+      postgres:
         image: postgres
         env:
           POSTGRES_PASSWORD: postgres
@@ -29,31 +22,30 @@ jobs:
           - 5432:5432
 
     steps:
-      - uses: actions/checkout@v2
-      - name: ACTIONS_ALLOW_UNSECURE_COMMANDS
-        id: ACTIONS_ALLOW_UNSECURE_COMMANDS
-        run: echo 'ACTIONS_ALLOW_UNSECURE_COMMANDS=true' >> $GITHUB_ENV
-
-      - name: Update stack
-        run: stack update
-      - uses: actions/cache@v2
-        name: Cache ~/.stack
+      - uses: actions/checkout@v4
+
+      - uses: cachix/install-nix-action@v30
         with:
-          path: ~/.stack
-          key: ${{ runner.os }}-stack-${{ hashFiles('stack.yaml') }}
-      - name: Build dependencies
-        run: |
-            stack build  --only-dependencies --fast
-
-      - uses: actions/cache@v2
-        name: Cache .stack-work
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: Cache cabal
+        uses: actions/cache@v4
         with:
-          path: .stack-work
-          key: ${{ runner.os }}-stack-${{ hashFiles('services/claims/package.yaml') }}
-      - name: Build domaindriven
-        run: |
-            stack build --fast
-      - name: Run tests
-        run: |
-            stack test --fast
+          path: |
+            ~/.cabal/store
+            ~/.cabal/packages
+            dist-newstyle
+          key: ${{ runner.os }}-cabal-${{ hashFiles('cabal.project', '**/*.cabal') }}
+          restore-keys: |
+            ${{ runner.os }}-cabal-
+
+      - name: Update package index
+        run: nix develop --command cabal update
 
+      - name: Build
+        run: nix develop --command cabal build all
+
+      - name: Run tests
+        run: nix develop --command cabal test all

.gitignore

@@ -5,3 +5,5 @@ stack.yaml.lock
 hie.yaml
 dist-newstyle/
 .vscode
+.repro
+ai_docs

CLAUDE.md

@@ -0,0 +1,53 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build Commands
+
+- **Build all packages**: `cabal build all`
+- **Build specific package**: `cabal build domaindriven`
+- **Run tests**: `cabal test all`
+- **Run specific test**: `cabal test domaindriven`
+- **Clean build**: `cabal clean`
+
+## Architecture Overview
+
+DomainDriven is a synchronous event sourcing and CQRS library split into multiple packages:
+
+### Core Components
+
+- **domaindriven-core**: Core persistence model with PostgreSQL and in-memory backends
+  - `ReadModel`/`WriteModel` type classes define the persistence interface
+  - `ForgetfulInMemory`: In-memory backend for testing/development
+  - `Postgres`: Production persistence with transactional guarantees
+  - Synchronous event sourcing with locks to avoid eventual consistency issues
+
+- **domaindriven**: Effectful-based API layer
+  - Uses standard Servant combinators instead of custom ones
+  - Two main effects: `Aggregate` (commands) and `Projection` (queries)
+  - Dynamic dispatch interpreters for different backends
+  - Located in `domaindriven/`
+
+### Key Design Patterns
+
+1. **Event Sourcing Model**:
+   - Model = current state (derived from events)
+   - Events = immutable history of changes
+   - `applyEvent :: Model -> Stored Event -> Model`
+
+2. **Command/Query Separation**:
+   - Commands emit events and may update state
+   - Queries are read-only operations
+   - Both can be composed hierarchically
+
+3. **Index Types**:
+   - `NoIndex` for single aggregates
+   - Custom index types for multiple aggregates
+   - Functional dependencies can reduce type parameters
+
+## Development Notes
+
+- All packages use extensive language extensions (see .cabal files)
+- Strict warning settings (`-Wall -Werror`) - fix all warnings before committing
+- The Effectful layer aims to simplify the API while maintaining type safety
+- Tests use `hspec` framework with in-memory backends

README.md

@@ -1,8 +1,11 @@
 # DomainDriven
 
-DomainDriven is a batteries included synchronous event sourcing and CQRS library. It is split into two parts:
+DomainDriven is a batteries included synchronous event sourcing and CQRS library. It is split into the following packages:
 
-- [domaindriven-core](domaindriven-core) Contains the core persistance model as well as postgres and in-memory backend.
-- [domaindriven](domaindriven) Introduces a convenient way of specifying actions using GADTs and TemplateHaskell.
+- [domaindriven-core](domaindriven-core) - Core persistence model with PostgreSQL and in-memory backends.
+- [domaindriven](domaindriven) - Effectful-based API layer with `Aggregate` and `Projection` effects, plus Servant integration.
+- [domaindriven-examples](domaindriven-examples) - Example applications demonstrating usage.
 
+## Design idea
 
+The core idea is to do synchronous event sourcing with locks and thereby provide the upsides of event sourcing without the extra complexity introduced by asynchronous workflows.

cabal.project

@@ -0,0 +1,10 @@
+packages:
+  shape-coerce/
+  domaindriven-core/
+  domaindriven/
+  domaindriven-examples/
+
+-- Use Stackage LTS 24.2 as the main package source
+import: https://www.stackage.org/lts-24.31/cabal.config
+
+with-compiler: ghc-9.10.3