More work on the stateful checker; still not perfect, but it's getting better

6 files changed, 294 insertions, 0 deletions

diff --git a/src/main/java/au/id/zancanaro/javacheck/state/Command.java b/src/main/java/au/id/zancanaro/javacheck/state/Command.java
new file mode 100644
index 0000000..afa3957
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/Command.java
@@ -0,0 +1,23 @@
+package au.id.zancanaro.javacheck.state;
+
+import au.id.zancanaro.javacheck.Generator;
+
+public abstract class Command<State,Args,Result> {
+    public Generator<Args> argsGenerator(State state) {
+        return Generator.pure(null);
+    }
+
+    public boolean preCondition(State state, Args args) {
+        return true;
+    }
+
+    public abstract Result runCommand(Args args);
+
+    public State nextState(State state, Args args, CommandValue<Result> result) {
+        return state;
+    }
+
+    public boolean postCondition(State oldState, State newState, Args args, Result result) {
+        return true;
+    }
+}
diff --git a/src/main/java/au/id/zancanaro/javacheck/state/CommandList.java b/src/main/java/au/id/zancanaro/javacheck/state/CommandList.java
new file mode 100644
index 0000000..0426fd3
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/CommandList.java
@@ -0,0 +1,91 @@
+package au.id.zancanaro.javacheck.state;
+
+import java.util.*;
+
+public class CommandList<State> {
+    private final List<GeneratedCommand<State, ?, ?>> commands;
+
+    public CommandList(List<GeneratedCommand<State, ?, ?>> commands) {
+        this.commands = new ArrayList<>(commands);
+    }
+
+    public CommandResult<State> run(State initialState) {
+        Map<Integer, Object> values = new HashMap<>();
+        CommandResult<State> result = CommandResult.success(initialState);
+        for (GeneratedCommand<State, ?, ?> generated : commands) {
+            result = runRealCommand(generated, result.getState(), values);
+            if (result.isFailed()) {
+                break;
+            }
+        }
+        return result;
+    }
+
+    private static <State, Args, Result> CommandResult<State> runRealCommand(
+            GeneratedCommand<State, Args, Result> generated,
+            State state,
+            Map<Integer, Object> values) {
+        int id = generated.getId();
+        Command<State, Args, Result> command = generated.getCommand();
+        Args args = generated.getArgs();
+        try {
+            if (!command.preCondition(state, args)) {
+                return CommandResult.fail(state, new Error("Precondition failed"));
+            }
+            Result result = CommandValue.withValues(values, () ->
+                    command.runCommand(args));
+            values.put(id, result);
+            final State oldState = state;
+            final State newState = CommandValue.withValues(values, () ->
+                    command.nextState(oldState, args, new CommandValue<>(id)));
+            state = newState;
+            if (!CommandValue.withValues(values, () -> command.postCondition(oldState, newState, args, result))) {
+                return CommandResult.fail(state, new Error("Postcondition failed"));
+            }
+            return CommandResult.success(state);
+        } catch (Throwable ex) {
+            return CommandResult.fail(state, ex);
+        }
+    }
+
+    private static <State, Args, Result> CommandResult<State> runAbstractCommand(
+            GeneratedCommand<State, Args, Result> generated,
+            State state) {
+        int id = generated.getId();
+        Command<State, Args, Result> command = generated.getCommand();
+        Args args = generated.getArgs();
+        try {
+            if (!command.preCondition(state, args)) {
+                return CommandResult.fail(state, new Error("Precondition failed"));
+            }
+            state = command.nextState(state, args, new CommandValue<>(id));
+            return CommandResult.success(state);
+        } catch (Throwable ex) {
+            return CommandResult.fail(state, ex);
+        }
+    }
+
+    public boolean isValid() {
+        CommandResult<State> result = CommandResult.success(null);
+        for (GeneratedCommand<State, ?, ?> generated : commands) {
+            result = runAbstractCommand(generated, result.getState());
+            if (result.isFailed()) {
+                break;
+            }
+        }
+        return !result.isFailed();
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        Iterator<GeneratedCommand<State, ?, ?>> iterator = commands.iterator();
+        while (iterator.hasNext()) {
+            builder.append(iterator.next());
+            if (iterator.hasNext()) {
+                builder.append(", ");
+            }
+        }
+        return builder.toString();
+    }
+}
diff --git a/src/main/java/au/id/zancanaro/javacheck/state/CommandListGenerator.java b/src/main/java/au/id/zancanaro/javacheck/state/CommandListGenerator.java
new file mode 100644
index 0000000..4c2c47f
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/CommandListGenerator.java
@@ -0,0 +1,50 @@
+package au.id.zancanaro.javacheck.state;
+
+import au.id.zancanaro.javacheck.Generator;
+import au.id.zancanaro.javacheck.ShrinkTree;
+
+import java.util.Random;
+import java.util.function.Function;
+
+import static au.id.zancanaro.javacheck.Generator.pure;
+import static au.id.zancanaro.javacheck.Generators.noShrink;
+
+public class CommandListGenerator<State> implements Generator<CommandList<State>> {
+    private final Function<State, Generator<Command<State, ?, ?>>> generateCommand;
+
+    public CommandListGenerator(Function<State, Generator<Command<State, ?, ?>>> generateCommand) {
+        this.generateCommand = generateCommand;
+    }
+
+    public Generator<GeneratedCommand<State, ?, ?>> commandGenerator(int id, State state) {
+        return noShrink(generateCommand.apply(state))
+                .flatMap(command -> generateSingleCommand(id, command, state));
+    }
+
+    public <Args, Result> Generator<GeneratedCommand<State, ?, ?>> generateSingleCommand(int id, Command<State, Args, Result> command, State state) {
+        return command.argsGenerator(state).flatMap(generatedArgs ->
+                command.preCondition(state, generatedArgs) ?
+                        pure(new GeneratedCommand<>(id, command, generatedArgs)) :
+                        commandGenerator(id, state));
+    }
+
+    public <Args, Result> State nextState(int id, GeneratedCommand<State, Args, Result> generatedCommand, State state) {
+        return generatedCommand.getCommand().nextState(state, generatedCommand.getArgs(), new CommandValue<>(id));
+    }
+
+    @Override
+    public ShrinkTree<CommandList<State>> generate(Random random, int size) {
+        int count = random.nextInt(size);
+        @SuppressWarnings("unchecked")
+        ShrinkTree<GeneratedCommand<State, ?, ?>>[] commandTrees = (ShrinkTree<GeneratedCommand<State, ?, ?>>[]) new ShrinkTree[count];
+        State state = null;
+        for (int i = 0; i < count; ++i) {
+            commandTrees[i] = commandGenerator(i, state).generate(random, size);
+            GeneratedCommand<State, ?, ?> generatedCommand = commandTrees[i].getValue();
+            state = nextState(i, generatedCommand, state);
+        }
+        return ShrinkTree.combine(commandTrees, ShrinkTree::removeAndPromoteChildren)
+                .map(list -> new CommandList<>(list))
+                .filter(CommandList::isValid);
+    }
+}
diff --git a/src/main/java/au/id/zancanaro/javacheck/state/CommandResult.java b/src/main/java/au/id/zancanaro/javacheck/state/CommandResult.java
new file mode 100644
index 0000000..12f650d
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/CommandResult.java
@@ -0,0 +1,31 @@
+package au.id.zancanaro.javacheck.state;
+
+public class CommandResult<State> {
+    private final State state;
+    private final Throwable thrown;
+
+    private CommandResult(State state, Throwable thrown) {
+        this.state = state;
+        this.thrown = thrown;
+    }
+
+    public State getState() {
+        return state;
+    }
+
+    public boolean isFailed() {
+        return thrown != null;
+    }
+
+    public Throwable getThrown() {
+        return thrown;
+    }
+
+    public static <State> CommandResult<State> success(State state) {
+        return new CommandResult<>(state, null);
+    }
+
+    public static <State> CommandResult<State> fail(State state, Throwable ex) {
+        return new CommandResult<>(state, ex);
+    }
+}
diff --git a/src/main/java/au/id/zancanaro/javacheck/state/CommandValue.java b/src/main/java/au/id/zancanaro/javacheck/state/CommandValue.java
new file mode 100644
index 0000000..8d3f272
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/CommandValue.java
@@ -0,0 +1,47 @@
+package au.id.zancanaro.javacheck.state;
+
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.function.Supplier;
+
+public class CommandValue<T> {
+    private static Map<Integer, Object> values = null;
+
+    public static <T> T withValues(Map<Integer, Object> newValues, Supplier<T> action) {
+        Map<Integer,Object> oldValues = values;
+        try {
+            values = newValues;
+            return action.get();
+        } finally {
+            values = oldValues;
+        }
+    }
+
+    private final int id;
+
+    public CommandValue(int id) {
+        this.id = id;
+    }
+
+    public boolean isAbstract() {
+        return values == null;
+    }
+
+    @SuppressWarnings("unchecked")
+    public T get() {
+        if (values.containsKey(getId())) {
+            return (T) values.get(getId());
+        } else {
+            throw new NoSuchElementException("Concrete values cannot be supplied prior to being calculated");
+        }
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public String toString() {
+        return "#{" + id + "}";
+    }
+}
diff --git a/src/main/java/au/id/zancanaro/javacheck/state/GeneratedCommand.java b/src/main/java/au/id/zancanaro/javacheck/state/GeneratedCommand.java
new file mode 100644
index 0000000..90d9a47
--- /dev/null
+++ b/src/main/java/au/id/zancanaro/javacheck/state/GeneratedCommand.java
@@ -0,0 +1,52 @@
+package au.id.zancanaro.javacheck.state;
+
+public class GeneratedCommand<State, Args, Result> {
+    private final int id;
+    private final Command<State, Args, Result> command;
+    private final Args args;
+
+    public GeneratedCommand(int id, Command<State, Args, Result> command, Args args) {
+        this.id = id;
+        this.command = command;
+        this.args = args;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public Command<State, Args, Result> getCommand() {
+        return command;
+    }
+
+    public Args getArgs() {
+        return args;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        GeneratedCommand that = (GeneratedCommand) o;
+
+        if (args != null ? !args.equals(that.args) : that.args != null)
+            return false;
+        if (command != null ? !command.equals(that.command) : that.command != null)
+            return false;
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = command != null ? command.hashCode() : 0;
+        result = 31 * result + (args != null ? args.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "#{" + id + "} = " + command + " <- " + args;
+    }
+}