// Establishes key-code definitions.
/// <reference path="codes.ts" />
// Defines our generalized "KeyEvent" class.
/// <reference path="keyEvent.ts" />

namespace com.keyman.text {
  export enum EmulationKeystrokes {
    Space = ' ',
    Enter = '\n',
    Backspace = '\b'
  }

  /**
   * Defines a collection of static library functions that define KeymanWeb's default (implied) keyboard rule behaviors.
   */
  export class DefaultOutput {
    private constructor() {
    }

    static codeForEvent(Lkc: KeyEvent) {
      return Codes.keyCodes[Lkc.kName] || Lkc.Lcode;;
    }

    /**
     * Serves as a default keycode lookup table.  This may be referenced safely by mnemonic handling without fear of side-effects.
     * Also used by Processor.defaultRuleBehavior to generate output after filtering for special cases.
     */
    public static forAny(Lkc: KeyEvent, isMnemonic: boolean) {
      var char = '';

      // A pretty simple table of lookups, corresponding VERY closely to the original defaultKeyOutput.
      if((char = DefaultOutput.forSpecialEmulation(Lkc)) != null) {
        return char;
      } else if(!isMnemonic && ((char = DefaultOutput.forNumpadKeys(Lkc)) != null)) {
        return char;
      } else if((char = DefaultOutput.forUnicodeKeynames(Lkc)) != null) {
        return char;
      } else if((char = DefaultOutput.forBaseKeys(Lkc)) != null) {
        return char;
      } else {
        // // For headless and embeddded, we may well allow '\t'.  It's DOM mode that has other uses.
        // // Not originally defined for text output within defaultKeyOutput.
        // // We can't enable it yet, as it'll cause hardware keystrokes in the DOM to output '\t' rather
        // // than rely on the browser-default handling.
        let code = DefaultOutput.codeForEvent(Lkc);
        switch(code) {
        //   case Codes.keyCodes['K_TAB']:
        //   case Codes.keyCodes['K_TABBACK']:
        //   case Codes.keyCodes['K_TABFWD']:
        //     return '\t';
          default:
           return '';
        }
      }
    }

    /**
     * isCommand - returns a boolean indicating if a non-text event should be triggered by the keystroke.
     */
    public static isCommand(Lkc: KeyEvent): boolean {
      let code = DefaultOutput.codeForEvent(Lkc);

      switch(code) {
        // Should we ever implement them:
        // case Codes.keyCodes['K_LEFT']:  // would not output text, but would alter the caret's position in the context.
        // case Codes.keyCodes['K_RIGHT']:
        //   return true;
        default:
          return false;
      }
    }

    /**
     * Used when a RuleBehavior represents a non-text "command" within the Engine.  This will generally 
     * trigger events that require context reset - often by moving the caret or by moving what OutputTarget
     * the caret is in.  However, we let those events perform the actual context reset.
     * 
     * Note:  is extended by DOM-aware KeymanWeb code.
     */
    public static applyCommand(Lkc: KeyEvent): void {
      // Notes for potential default-handling extensions:
      // 
      // switch(code) {
        // // Problem:  clusters, and doing them right.
        // // The commented-out code below should be a decent starting point, but clusters make it complex.
        // // Mostly based on pre-12.0 code, but the general idea should be relatively clear.
        //
        // case Codes.keyCodes['K_LEFT']:
        //   if(touchAlias) {
        //     var caretPos = keymanweb.getTextCaret(Lelem);
        //     keymanweb.setTextCaret(Lelem, caretPos - 1 >= 0 ? caretPos - 1 : 0);
        //   }
        //   break;
        // case Codes.keyCodes['K_RIGHT']:
        //   if(touchAlias) {
        //     var caretPos = keymanweb.getTextCaret(Lelem);
        //     keymanweb.setTextCaret(Lelem, caretPos + 1);
        //   }
        //   if(code == VisualKeyboard.keyCodes['K_RIGHT']) {
        //     break;
        //   }
      // }
      //
      // Note that these would be useful even outside of a DOM context.
    }

    /**
     * Codes matched here generally have default implementations when in a browser but require emulation
     * for 'synthetic' `OutputTarget`s like `Mock`s, which have no default text handling.
     */
    public static forSpecialEmulation(Lkc: KeyEvent): EmulationKeystrokes {
      let code = DefaultOutput.codeForEvent(Lkc);

      switch(code) {
        case Codes.keyCodes['K_BKSP']:
          return EmulationKeystrokes.Backspace;
        case Codes.keyCodes['K_ENTER']:
          return EmulationKeystrokes.Enter;
        // (Probably) only here for legacy reasons; it's always been handled alongside the other two.
        case Codes.keyCodes['K_SPACE']:
          return EmulationKeystrokes.Space;
        // case Codes.keyCodes['K_DEL']:
        //   return '\u007f'; // 127, ASCII / Unicode control code for DEL.
        default:
          return null;
      }
    }

    // Should not be used for mnenomic keyboards.  forAny()'s use of this method checks first.
    public static forNumpadKeys(Lkc: KeyEvent) {
      // Translate numpad keystrokes into their non-numpad equivalents
      if(Lkc.Lcode >= Codes.keyCodes["K_NP0"]  &&  Lkc.Lcode <= Codes.keyCodes["K_NPSLASH"]) {
        // Number pad, numlock on
        if(Lkc.Lcode < 106) {
          var Lch = Lkc.Lcode-48;
        } else {
          Lch = Lkc.Lcode-64;
        }
        let ch = String._kmwFromCharCode(Lch); //I3319
        return ch;
      } else {
        return null;
      }
    }

    // Test for fall back to U_xxxxxx key id
    // For this first test, we ignore the keyCode and use the keyName
    public static forUnicodeKeynames(Lkc: KeyEvent, ruleBehavior?: RuleBehavior) {
      let keyName = Lkc.kName;

      // Test for fall back to U_xxxxxx key id
      // For this first test, we ignore the keyCode and use the keyName
      if(!keyName || keyName.substr(0,2) != 'U_') {
        return null;
      }
    
      var codePoint = parseInt(keyName.substr(2,6), 16);
      if (((0x0 <= codePoint) && (codePoint <= 0x1F)) || ((0x80 <= codePoint) && (codePoint <= 0x9F))) {
        // Code points [U_0000 - U_001F] and [U_0080 - U_009F] refer to Unicode C0 and C1 control codes.
        // Check the codePoint number and do not allow output of these codes via U_xxxxxx shortcuts.
        if(ruleBehavior) {
          ruleBehavior.errorLog = ("Suppressing Unicode control code: U_00" + codePoint.toString(16));
        }
        return null;
      } else {
        // String.fromCharCode() is inadequate to handle the entire range of Unicode
        // Someday after upgrading to ES2015, can use String.fromCodePoint()
        return String.kmwFromCharCode(codePoint);
      }
    }

    // Test for otherwise unimplemented keys on the the base default & shift layers.
    // Those keys must be blocked by keyboard rules if intentionally unimplemented; otherwise, this function will trigger.
    public static forBaseKeys(Lkc: KeyEvent, ruleBehavior?: RuleBehavior) {
      let n = Lkc.Lcode;
      let keyShiftState = Lkc.Lmodifiers;

      // check if exact match to SHIFT's code.  Only the 'default' and 'shift' layers should have default key outputs.
      // TODO:  Extend to allow AltGr as well - better mnemonic support.
      if(keyShiftState == Codes.modifierCodes['SHIFT']) {
        keyShiftState = 1;
      } else if(keyShiftState != 0) {
        if(ruleBehavior) {
          ruleBehavior.warningLog = "KMW only defines default key output for the 'default' and 'shift' layers!";
        }
        return null;
      }

      // Now that keyShiftState is either 0 or 1, we can use the following structure to determine the default output.
      try {
        if(n >= Codes.keyCodes['K_0'] && n <= Codes.keyCodes['K_9']) { // The number keys.
          return Codes.codesUS[keyShiftState][0][n-Codes.keyCodes['K_0']];
        } else if(n >= Codes.keyCodes['K_A'] && n <= Codes.keyCodes['K_Z']) { // The base letter keys
          return String.fromCharCode(n+(keyShiftState?0:32));  // 32 is the offset from uppercase to lowercase.
        } else if(n >= Codes.keyCodes['K_COLON'] && n <= Codes.keyCodes['K_BKQUOTE']) {
          return Codes.codesUS[keyShiftState][1][n-Codes.keyCodes['K_COLON']];
        } else if(n >= Codes.keyCodes['K_LBRKT'] && n <= Codes.keyCodes['K_QUOTE']) {
          return Codes.codesUS[keyShiftState][2][n-Codes.keyCodes['K_LBRKT']];
        }
      } catch (e) {
        if(ruleBehavior) {
          ruleBehavior.errorLog = "Error detected with default mapping for key:  code = " + n + ", shift state = " + (keyShiftState == 1 ? 'shift' : 'default');
        }
      }

      return null;
    }
  }
}