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Apply OneOf to Todo; tidy
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@bartelink
bartelink committed Jan 17, 2019
1 parent b53afb1 commit 4695a3e
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Showing 2 changed files with 33 additions and 56 deletions.
8 changes: 4 additions & 4 deletions equinox-web-csharp/Domain/Aggregate.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,11 @@
using Equinox.Store;
using Microsoft.FSharp.Core;
using Newtonsoft.Json;
using OneOf;
using Serilog;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using OneOf;

namespace TodoBackendTemplate
{
Expand Down Expand Up @@ -46,8 +46,8 @@ public class State

static void Evolve(State s, Event x) =>
x.Match(
(Happened _) => s.Happened = true,
(Compacted e) => s.Happened = e.Happened);
(Event.Happened _) => s.Happened = true,
(Event.Compacted e) => s.Happened = e.Happened);

public static State Fold(State origin, IEnumerable<Event> xs)
{
Expand All @@ -71,7 +71,7 @@ public class MakeItSo : Command
}

public static Event[] Interpret(State s, Command x) =>
x.Match(makeItSo =>
x.Match((MakeItSo _) =>
s.Happened ? new Event[0] : new Event [] { new Event.Happened()});
}

Expand Down
81 changes: 29 additions & 52 deletions equinox-web-csharp/Domain/Todo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
using Equinox.Store;
using Microsoft.FSharp.Core;
using Newtonsoft.Json;
using OneOf;
using Serilog;
using System;
using System.Collections.Generic;
Expand All @@ -14,6 +15,7 @@ public static class Todo
{
/// NB - these types and names reflect the actual storage formats and hence need to be versioned with care
public abstract class Event
: OneOfBase<Event.Added, Event.Updated, Event.Deleted, Event.Cleared, Event.Compacted>
{
/// Information we retain per Todo List entry
public abstract class ItemData
Expand Down Expand Up @@ -95,37 +97,23 @@ public static State Fold(State origin, IEnumerable<Event> xs)
var nextId = origin.NextId;
var items = origin.Items.ToList();
foreach (var x in xs)
switch (x)
{
case Event.Added e:
nextId++;
items.Insert(0, e.Data);
break;
case Event.Updated e:
x.Switch(
(Event.Added e) => { nextId++; items.Insert(0, e.Data); },
(Event.Updated e) =>
{
var i = items.FindIndex(item => item.Id == e.Data.Id);
if (i != -1)
items[i] = e.Data;
break;
case Event.Deleted e:
items.RemoveAll(item => item.Id == e.Id);
break;
case Event.Cleared e:
nextId = e.NextId;
items.Clear();
break;
case Event.Compacted e:
nextId = e.NextId;
items = e.Items.ToList();
break;
default:
throw new ArgumentOutOfRangeException(nameof(x), x, "invalid");
}
},
(Event.Deleted e) => items.RemoveAll(item => item.Id == e.Id),
(Event.Cleared e) => { nextId = e.NextId; items.Clear(); },
(Event.Compacted e) => { nextId = e.NextId; items = e.Items.ToList(); });
return new State(nextId, items.ToArray());
}

/// Determines whether a given event represents a checkpoint that implies we don't need to see any preceding events
public static bool IsOrigin(Event e) => e is Event.Cleared || e is Event.Compacted;

/// Prepares an Event that encodes all relevant aspects of a State such that `evolve` can rehydrate a complete State from it
public static Event Compact(State state) => new Event.Compacted { NextId = state.NextId, Items = state.Items };
}
Expand All @@ -140,6 +128,7 @@ public class Props

/// Defines the operations a caller can perform on a Todo List
public abstract class Command
: OneOfBase<Command.Add, Command.Update, Command.Delete, Command.Clear>
{
/// Create a single item
public class Add : Command
Expand All @@ -166,38 +155,26 @@ public class Clear : Command
}

/// Defines the decision process which maps from the intent of the `Command` to the `Event`s that represent that decision in the Stream
public static IEnumerable<Event> Interpret(State s, Command x)
{
switch (x)
{
case Add c:
yield return Make<Event.Added>(s.NextId, c.Props);
break;
case Update c:
var proposed = new {c.Props.Order, c.Props.Title, c.Props.Completed};
public static IEnumerable<Event> Interpret(State s, Command x) =>
x.Match(
(Add c) => new Event[] { Make<Event.Added>(s.NextId, c.Props) },
(Update c) =>
{
var proposed = new { c.Props.Order, c.Props.Title, c.Props.Completed };
bool IsEquivalent(Event.ItemData i) =>
i.Id == c.Id
&& new {i.Order, i.Title, i.Completed} == proposed;

if (!s.Items.Any(IsEquivalent))
yield return Make<Event.Updated>(c.Id, c.Props);
break;
case Delete c:
if (s.Items.Any(i => i.Id == c.Id))
yield return new Event.Deleted {Id = c.Id};
break;
case Clear _:
if (s.Items.Any()) yield return new Event.Cleared {NextId = s.NextId};
break;

default:
throw new ArgumentOutOfRangeException(nameof(x), x, "invalid");
}
&& new { i.Order, i.Title, i.Completed } == proposed;
T Make<T>(int id, Props value) where T : Event.ItemEvent, new() =>
new T {Data = {Id = id, Order = value.Order, Title = value.Title, Completed = value.Completed}};
}
if (s.Items.Any(IsEquivalent))
return Enumerable.Empty<Event>();
return new[] { Make<Event.Updated>(c.Id, c.Props) };
},
(Delete c) => s.Items.Any(i => i.Id == c.Id) ? new Event[] { new Event.Deleted { Id = c.Id } } : new Event[0],
(Clear _) => s.Items.Any() ? new Event[] { new Event.Cleared { NextId = s.NextId } } : new Event[0]);

static T Make<T>(int id, Props value) where T : Event.ItemEvent, new() =>
new T { Data = { Id = id, Order = value.Order, Title = value.Title, Completed = value.Completed } };
}

/// Defines low level stream operations relevant to the Todo Stream in terms of Command and Events
Expand Down

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