// Copyright 2010 Google Inc. All Rights Reserved.
package org.waveprotocol.wave.model.document;

import org.waveprotocol.wave.model.util.StringMap;


public interface AnnotationBehaviour {
  /** Bias priority for 'container' elements, which bias inwards. */
  public static double ELEMENT_PRIORITY = 5.0;

  /** Bias priority for the default behaviour, placing it behind elements. */
  public static double DEFAULT_PRIORITY = 1.0;

  /** Cursor movements which may affect bias. */
  public enum CursorDirection {
    /** Last movement was to the left. */
    FROM_LEFT,
    /** Last movement was to the right. */
    FROM_RIGHT,
    /** Last movement was unknown or doesn't affect bias. */
    NEUTRAL;

    /** Converts the last cursor movement into a default bias. */
    public static BiasDirection toBiasDirection(CursorDirection cursor) {
      switch (cursor) {
        case FROM_LEFT:
          return BiasDirection.LEFT;
        case FROM_RIGHT:
          return BiasDirection.RIGHT;
      }
      return BiasDirection.NEITHER;
    }
  }

  /** Which 'side' of the gap the cursor is in. */
  public enum BiasDirection {
    /** A)  B -- default = assoicated with the previous character */
    LEFT,
    /** A  (B -- associated with the next character. */
    RIGHT,
    /** A | B -- right in the middle = unknown. */
    NEITHER;
  }

  /** Which 'side' of the cursor to inherit the annotation from. */
  public enum InheritDirection {
    /** inherit the annotation from the side the cursor is biassed. */
    INSIDE,
    /** inherit the annotation from the side other side to which the cursor is biassed. */
    OUTSIDE,
    /** do not inherit annotation (null is used instead). */
    NEITHER;
  }

  /** If required, indicates what type of content is being inserted and may require annotations. */
  public enum ContentType {
    /** normal text, unstyled. */
    PLAIN_TEXT,
    /** rich text with its own stylings. */
    RICH_TEXT,
  }

  /**
   * Shows the priority of this behaviour - behaviours with lower priority value get precedence
   * in setting the bias direction.
   */
  double getPriority();

  /**
   * Defines the desired bias of the cursor given the current state of annotations.
   *
   * @param left Key-Value mappings for annotations to the left of the cursor.
   * @param right Key-Value mappings for annotations to the right of the cursor.
   * @param cursor last known value for the cursor movement.
   * @return Desired bias direction.
   */
  BiasDirection getBias(StringMap<Object> left, StringMap<Object> right, CursorDirection cursor);

  /**
   * Defines which side of the cursor to inherit annotations from, given the current state of
   * annotations and some information about what the annotations are being set over.
   * Note that in the case of ranged selections being replaced, the cursor is considered to have
   * the same annotations as the first character of the selected range.
   *
   * @param inside Key-Value mappings for annotations inside the cursor.
   * @param outside Key-Value mappings for annotations outside the cursor.
   * @param type Type of content being replaced
   * @return Desired inheritence behaviour.
   */
  InheritDirection replace(StringMap<Object> inside, StringMap<Object> outside, ContentType type);

  /**
   * Defines the default model behaviour for annotations - that is, does not specify a bias,
   * replacement always comes from inside the cursor, and is prioritised behind elements.
   */
  public static class DefaultAnnotationBehaviour implements AnnotationBehaviour {
    @Override
    public BiasDirection getBias(StringMap<Object> left, StringMap<Object> right,
        CursorDirection cursor) {
      return BiasDirection.NEITHER;
    }
    @Override
    public double getPriority() {
      return DEFAULT_PRIORITY;
    }
    @Override
    public InheritDirection replace(StringMap<Object> inside, StringMap<Object> outside,
        ContentType type) {
      // Default behaviour: inherit, unless rich text in which case leave formatting as-is
      return type == ContentType.RICH_TEXT ? InheritDirection.NEITHER : InheritDirection.INSIDE;
    }
  }
}