package com.bumptech.glide.request;

import android.support.annotation.Nullable;

/**
 * Runs a single primary {@link Request} until it completes and then a fallback error request only
 * if the single primary request fails.
 */
public final class ErrorRequestCoordinator implements RequestCoordinator, Request {

    @Nullable
    private final RequestCoordinator parent;
    private Request primary;
    private Request error;

    public ErrorRequestCoordinator(@Nullable RequestCoordinator parent) {
        this.parent = parent;
    }

    public void setRequests(Request primary, Request error) {
        this.primary = primary;
        this.error = error;
    }

    @Override
    public void begin() {
        if (!primary.isRunning()) {
            primary.begin();
        }
    }

    @Override
    public void clear() {
        primary.clear();
        // Don't check primary.isFailed() here because it will have been reset by the clear call
        // immediately before this.
        if (error.isRunning()) {
            error.clear();
        }
    }

    @Override
    public boolean isRunning() {
        return primary.isFailed() ? error.isRunning() : primary.isRunning();
    }

    @Override
    public boolean isComplete() {
        return primary.isFailed() ? error.isComplete() : primary.isComplete();
    }

    @Override
    public boolean isResourceSet() {
        return primary.isFailed() ? error.isResourceSet() : primary.isResourceSet();
    }

    @Override
    public boolean isCleared() {
        return primary.isFailed() ? error.isCleared() : primary.isCleared();
    }

    @Override
    public boolean isFailed() {
        return primary.isFailed() && error.isFailed();
    }

    @Override
    public void recycle() {
        primary.recycle();
        error.recycle();
    }

    @Override
    public boolean isEquivalentTo(Request o) {
        if (o instanceof ErrorRequestCoordinator) {
            ErrorRequestCoordinator other = (ErrorRequestCoordinator) o;
            return primary.isEquivalentTo(other.primary) && error.isEquivalentTo(other.error);
        }
        return false;
    }

    @Override
    public boolean canSetImage(Request request) {
        return parentCanSetImage() && isValidRequest(request);
    }

    private boolean parentCanSetImage() {
        return parent == null || parent.canSetImage(this);
    }

    @Override
    public boolean canNotifyStatusChanged(Request request) {
        return parentCanNotifyStatusChanged() && isValidRequest(request);
    }

    @Override
    public boolean canNotifyCleared(Request request) {
        return parentCanNotifyCleared() && isValidRequest(request);
    }

    private boolean parentCanNotifyCleared() {
        return parent == null || parent.canNotifyCleared(this);
    }

    private boolean parentCanNotifyStatusChanged() {
        return parent == null || parent.canNotifyStatusChanged(this);
    }

    private boolean isValidRequest(Request request) {
        return request.equals(primary) || (primary.isFailed() && request.equals(error));
    }

    @Override
    public boolean isAnyResourceSet() {
        return parentIsAnyResourceSet() || isResourceSet();
    }

    private boolean parentIsAnyResourceSet() {
        return parent != null && parent.isAnyResourceSet();
    }

    @Override
    public void onRequestSuccess(Request request) {
        if (parent != null) {
            parent.onRequestSuccess(this);
        }
    }

    @Override
    public void onRequestFailed(Request request) {
        if (!request.equals(error)) {
            if (!error.isRunning()) {
                error.begin();
            }
            return;
        }

        if (parent != null) {
            parent.onRequestFailed(this);
        }
    }
}
