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// Copyright 2015-2024 Nstream, inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package swim.system.lane;

import java.util.AbstractMap;
import java.util.Iterator;
import java.util.Map;
import swim.api.Lane;
import swim.api.Link;
import swim.api.SwimContext;
import swim.api.agent.AgentContext;
import swim.api.lane.ValueLane;
import swim.api.warp.function.DidCommand;
import swim.api.warp.function.DidEnter;
import swim.api.warp.function.DidLeave;
import swim.api.warp.function.DidUplink;
import swim.api.warp.function.WillCommand;
import swim.api.warp.function.WillEnter;
import swim.api.warp.function.WillLeave;
import swim.api.warp.function.WillUplink;
import swim.concurrent.Cont;
import swim.observable.function.DidSet;
import swim.observable.function.WillSet;
import swim.streamlet.Inlet;
import swim.streamlet.Outlet;
import swim.structure.Form;
import swim.system.warp.WarpLaneView;
import swim.util.Cursor;

public class ValueLaneView extends WarpLaneView implements ValueLane {

  protected final AgentContext agentContext;
  protected Form valueForm;
  protected ValueLaneModel laneBinding;
  protected int flags;

  protected Outlet input;
  protected Inlet[] outputs; // TODO: unify with observers
  protected int version;

  ValueLaneView(AgentContext agentContext, Form valueForm, int flags, Object observers) {
    super(observers);
    this.agentContext = agentContext;
    this.valueForm = valueForm;
    this.laneBinding = null;
    this.flags = flags;

    this.input = null;
    this.outputs = null;
    this.version = -1;
  }

  public ValueLaneView(AgentContext agentContext, Form valueForm) {
    this(agentContext, valueForm, 0, null);
  }

  @Override
  public AgentContext agentContext() {
    return this.agentContext;
  }

  @Override
  public ValueLaneModel laneBinding() {
    return this.laneBinding;
  }

  void setLaneBinding(ValueLaneModel laneBinding) {
    this.laneBinding = laneBinding;
  }

  @Override
  public ValueLaneModel createLaneBinding() {
    return new ValueLaneModel(this.flags);
  }

  @Override
  public final Form valueForm() {
    return this.valueForm;
  }

  @Override
  public  ValueLaneView valueForm(Form valueForm) {
    return new ValueLaneView(this.agentContext, valueForm, this.flags,
                                 this.typesafeObservers(this.observers));
  }

  @Override
  public  ValueLaneView valueClass(Class valueClass) {
    return this.valueForm(Form.forClass(valueClass));
  }

  public void setValueForm(Form valueForm) {
    this.valueForm = valueForm;
  }

  protected Object typesafeObservers(Object observers) {
    // TODO: filter out WillSet, DidSet
    return observers;
  }

  @Override
  public final boolean isResident() {
    return (this.flags & ValueLaneView.RESIDENT) != 0;
  }

  @Override
  public ValueLaneView isResident(boolean isResident) {
    this.didSetResident(isResident);

    // note: marked final given access of concurrently accessed volatile objects
    final ValueLaneModel laneBinding = this.laneBinding;

    if (laneBinding != null) {
      laneBinding.isResident(isResident);
    }

    return this;
  }

  void didSetResident(boolean isResident) {
    if (isResident) {
      this.flags |= ValueLaneView.RESIDENT;
    } else {
      this.flags &= ~ValueLaneView.RESIDENT;
    }
  }

  @Override
  public final boolean isTransient() {
    return (this.flags & ValueLaneView.TRANSIENT) != 0;
  }

  @Override
  public ValueLaneView isTransient(boolean isTransient) {
    this.didSetTransient(isTransient);

    // note: marked final given access of concurrently accessed volatile objects
    final ValueLaneModel laneBinding = this.laneBinding;

    if (laneBinding != null) {
      laneBinding.isTransient(isTransient);
    }

    return this;
  }

  void didSetTransient(boolean isTransient) {
    if (isTransient) {
      this.flags |= ValueLaneView.TRANSIENT;
    } else {
      this.flags &= ~ValueLaneView.TRANSIENT;
    }
  }

  @Override
  public void close() {
    this.laneBinding.closeLaneView(this);
  }

  @Override
  public ValueLaneView observe(Object observer) {
    super.observe(observer);
    return this;
  }

  @Override
  public ValueLaneView unobserve(Object observer) {
    super.unobserve(observer);
    return this;
  }

  @Override
  public ValueLaneView willSet(WillSet willSet) {
    return this.observe(willSet);
  }

  @Override
  public ValueLaneView didSet(DidSet didSet) {
    return this.observe(didSet);
  }

  @Override
  public ValueLaneView willCommand(WillCommand willCommand) {
    return this.observe(willCommand);
  }

  @Override
  public ValueLaneView didCommand(DidCommand didCommand) {
    return this.observe(didCommand);
  }

  @Override
  public ValueLaneView willUplink(WillUplink willUplink) {
    return this.observe(willUplink);
  }

  @Override
  public ValueLaneView didUplink(DidUplink didUplink) {
    return this.observe(didUplink);
  }

  @Override
  public ValueLaneView willEnter(WillEnter willEnter) {
    return this.observe(willEnter);
  }

  @Override
  public ValueLaneView didEnter(DidEnter didEnter) {
    return this.observe(didEnter);
  }

  @Override
  public ValueLaneView willLeave(WillLeave willLeave) {
    return this.observe(willLeave);
  }

  @Override
  public ValueLaneView didLeave(DidLeave didLeave) {
    return this.observe(didLeave);
  }

  @SuppressWarnings("unchecked")
  public Map.Entry dispatchWillSet(Link link, V newValue, boolean preemptive) {
    final Lane oldLane = SwimContext.getLane();
    final Link oldLink = SwimContext.getLink();
    try {
      SwimContext.setLane(this);
      SwimContext.setLink(link);
      final Object observers = this.observers;
      boolean complete = true;
      if (observers instanceof WillSet) {
        if (((WillSet) observers).isPreemptive() == preemptive) {
          try {
            newValue = ((WillSet) observers).willSet(newValue);
          } catch (Throwable error) {
            if (Cont.isNonFatal(error)) {
              this.laneDidFail(error);
            }
            throw error;
          }
        } else if (preemptive) {
          complete = false;
        }
      } else if (observers instanceof Object[]) {
        final Object[] array = (Object[]) observers;
        for (int i = 0, n = array.length; i < n; i += 1) {
          final Object observer = array[i];
          if (observer instanceof WillSet) {
            if (((WillSet) observer).isPreemptive() == preemptive) {
              try {
                newValue = ((WillSet) observer).willSet(newValue);
              } catch (Throwable error) {
                if (Cont.isNonFatal(error)) {
                  this.laneDidFail(error);
                }
                throw error;
              }
            } else if (preemptive) {
              complete = false;
            }
          }
        }
      }
      return new AbstractMap.SimpleImmutableEntry(complete, newValue);
    } finally {
      SwimContext.setLink(oldLink);
      SwimContext.setLane(oldLane);
    }
  }

  @SuppressWarnings("unchecked")
  public boolean dispatchDidSet(Link link, V newValue, V oldValue, boolean preemptive) {
    final Lane oldLane = SwimContext.getLane();
    final Link oldLink = SwimContext.getLink();
    try {
      SwimContext.setLane(this);
      SwimContext.setLink(link);
      final Object observers = this.observers;
      boolean complete = true;
      if (observers instanceof DidSet) {
        if (((DidSet) observers).isPreemptive() == preemptive) {
          try {
            ((DidSet) observers).didSet(newValue, oldValue);
          } catch (Throwable error) {
            if (Cont.isNonFatal(error)) {
              this.laneDidFail(error);
            }
            throw error;
          }
        } else if (preemptive) {
          complete = false;
        }
      } else if (observers instanceof Object[]) {
        final Object[] array = (Object[]) observers;
        for (int i = 0, n = array.length; i < n; i += 1) {
          final Object observer = array[i];
          if (observer instanceof DidSet) {
            if (((DidSet) observer).isPreemptive() == preemptive) {
              try {
                ((DidSet) observer).didSet(newValue, oldValue);
              } catch (Throwable error) {
                if (Cont.isNonFatal(error)) {
                  this.laneDidFail(error);
                }
                throw error;
              }
            } else if (preemptive) {
              complete = false;
            }
          }
        }
      }
      return complete;
    } finally {
      SwimContext.setLink(oldLink);
      SwimContext.setLane(oldLane);
    }
  }

  public V laneWillSet(V newValue) {
    return newValue;
  }

  public void laneDidSet(V newValue, V oldValue) {
    this.decohere();
    this.recohere(0); // TODO: debounce and track version
  }

  @Override
  public V get() {
    V state = this.valueForm.cast(this.laneBinding.get());
    if (state == null) {
      state = this.valueForm.unit();
    }
    return state;
  }

  @Override
  public V set(V newValue) {
    return this.laneBinding.set(this, newValue);
  }

  @Override
  public Outlet input() {
    return this.input;
  }

  @Override
  public void bindInput(Outlet input) {
    if (this.input != null) {
      this.input.unbindOutput(this);
    }
    this.input = input;
    if (this.input != null) {
      this.input.bindOutput(this);
    }
  }

  @Override
  public void unbindInput() {
    if (this.input != null) {
      this.input.unbindOutput(this);
    }
    this.input = null;
  }

  @Override
  public void disconnectInputs() {
    final Outlet input = this.input;
    if (input != null) {
      input.unbindOutput(this);
      this.input = null;
      input.disconnectInputs();
    }
  }

  @Override
  public Iterator> outputIterator() {
    return this.outputs != null ? Cursor.array(this.outputs) : Cursor.empty();
  }

  @SuppressWarnings("unchecked")
  @Override
  public void bindOutput(Inlet output) {
    final Inlet[] oldOutputs = this.outputs;
    final int n = oldOutputs != null ? oldOutputs.length : 0;
    final Inlet[] newOutputs = (Inlet[]) new Inlet[n + 1];
    if (n > 0) {
      System.arraycopy(oldOutputs, 0, newOutputs, 0, n);
    }
    newOutputs[n] = output;
    this.outputs = newOutputs;
  }

  @SuppressWarnings("unchecked")
  @Override
  public void unbindOutput(Inlet output) {
    final Inlet[] oldOutputs = this.outputs;
    final int n = oldOutputs != null ? oldOutputs.length : 0;
    for (int i = 0; i < n; i += 1) {
      if (oldOutputs[i] == output) {
        if (n > 1) {
          final Inlet[] newOutputs = (Inlet[]) new Inlet[n - 1];
          System.arraycopy(oldOutputs, 0, newOutputs, 0, i);
          System.arraycopy(oldOutputs, i + 1, newOutputs, i, (n - 1) - i);
          this.outputs = newOutputs;
        } else {
          this.outputs = null;
        }
        break;
      }
    }
  }

  @Override
  public void unbindOutputs() {
    final Inlet[] outputs = this.outputs;
    if (outputs != null) {
      this.outputs = null;
      for (int i = 0, n = outputs.length; i < n; i += 1) {
        final Inlet output = outputs[i];
        output.unbindInput();
      }
    }
  }

  @Override
  public void disconnectOutputs() {
    final Inlet[] outputs = this.outputs;
    if (outputs != null) {
      this.outputs = null;
      for (int i = 0, n = outputs.length; i < n; i += 1) {
        final Inlet output = outputs[i];
        output.unbindInput();
        output.disconnectOutputs();
      }
    }
  }

  @Override
  public void decohereOutput() {
    this.decohere();
  }

  @Override
  public void decohereInput() {
    this.decohere();
  }

  public void decohere() {
    if (this.version >= 0) {
      this.willDecohere();
      this.version = -1;
      this.onDecohere();
      final int n = this.outputs != null ? this.outputs.length : 0;
      for (int i = 0; i < n; i += 1) {
        this.outputs[i].decohereOutput();
      }
      this.didDecohere();
    }
  }

  @Override
  public void recohereOutput(int version) {
    this.recohere(version);
  }

  @Override
  public void recohereInput(int version) {
    this.recohere(version);
  }

  public void recohere(int version) {
    if (this.version < 0) {
      this.willRecohere(version);
      this.version = version;
      if (this.input != null) {
        this.input.recohereInput(version);
      }
      this.onRecohere(version);
      final int n = this.outputs != null ? this.outputs.length : 0;
      for (int i = 0; i < n; i += 1) {
        this.outputs[i].recohereOutput(version);
      }
      this.didRecohere(version);
    }
  }

  protected void willDecohere() {
    // hook
  }

  protected void onDecohere() {
    // hook
  }

  protected void didDecohere() {
    // hook
  }

  protected void willRecohere(int version) {
    // hook
  }

  protected void onRecohere(int version) {
    if (this.input != null) {
      final V value = this.input.get();
      this.set(value);
    }
  }

  protected void didRecohere(int version) {
    // hook
  }

  static final int RESIDENT = 1 << 0;
  static final int TRANSIENT = 1 << 1;

}