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package com.litongjava.tio.boot.paranamer;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * Default implementation of Paranamer reads from a post-compile added field
 * called '__PARANAMER_DATA'
 *
 * @author Paul Hammant
 * @author Mauro Talevi
 * @author Guilherme Silveira
 */
public class DefaultParanamer implements Paranamer {

  private static final String COMMA = ",";
  private static final String SPACE = " ";

  public static final String __PARANAMER_DATA = "v1.0 \n" + "lookupParameterNames java.lang.AccessibleObject methodOrConstructor \n"
      + "lookupParameterNames java.lang.AccessibleObject,boolean methodOrCtor,throwExceptionIfMissing \n"
      + "getParameterTypeName java.lang.Class cls\n";

  public DefaultParanamer() {
  }

  public String[] lookupParameterNames(AccessibleObject methodOrConstructor) {
    return lookupParameterNames(methodOrConstructor, true);
  }

  public String[] lookupParameterNames(AccessibleObject methodOrCtor, boolean throwExceptionIfMissing) {
    // Oh for some commonality between Constructor and Method !!
    Class[] types = null;
    Class declaringClass = null;
    String name = null;
    if (methodOrCtor instanceof Method) {
      Method method = (Method) methodOrCtor;
      types = method.getParameterTypes();
      name = method.getName();
      declaringClass = method.getDeclaringClass();
    } else {
      Constructor constructor = (Constructor) methodOrCtor;
      types = constructor.getParameterTypes();
      declaringClass = constructor.getDeclaringClass();
      name = "";
    }

    if (types.length == 0) {
      return EMPTY_NAMES;
    }
    final String parameterTypeNames = getParameterTypeNamesCSV(types);
    final String[] names = getParameterNames(declaringClass, parameterTypeNames, name + SPACE);
    if (names == null) {
      if (throwExceptionIfMissing) {
        throw new ParameterNamesNotFoundException(
            "No parameter names found for class '" + declaringClass + "', methodOrCtor " + name + " and parameter types " + parameterTypeNames);
      } else {
        return Paranamer.EMPTY_NAMES;
      }
    }
    return names;
  }

  private static String[] getParameterNames(Class declaringClass, String parameterTypes, String prefix) {
    String data = getParameterListResource(declaringClass);
    String line = findFirstMatchingLine(data, prefix + parameterTypes + SPACE);
    String[] parts = line.split(SPACE);
    // assumes line structure: constructorName parameterTypes parameterNames
    if (parts.length == 3 && parts[1].equals(parameterTypes)) {
      String parameterNames = parts[2];
      return parameterNames.split(COMMA);
    }
    return Paranamer.EMPTY_NAMES;
  }

  static String getParameterTypeNamesCSV(Class[] parameterTypes) {
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < parameterTypes.length; i++) {
      sb.append(getParameterTypeName(parameterTypes[i]));
      if (i < parameterTypes.length - 1) {
        sb.append(COMMA);
      }
    }
    return sb.toString();
  }

  private static String getParameterListResource(Class declaringClass) {
    try {
      Field field = declaringClass.getDeclaredField("__PARANAMER_DATA");
      // TODO create acc test which finds field?
      // TODO create acc test which does not find field?
      // TODO create acc test what to do with private? access anyway?
      // TODO create acc test with non static field?
      // TODO create acc test with another type of field?
      if (!Modifier.isStatic(field.getModifiers()) || !field.getType().equals(String.class)) {
        return null;
      }
      return (String) field.get(null);
    } catch (NoSuchFieldException e) {
      return null;
    } catch (IllegalAccessException e) {
      return null;
    }
  }

  /**
   * Filter the mappings and only return lines matching the prefix passed in.
   * 
   * @param data   the data encoding the mappings
   * @param prefix the String prefix
   * @return A list of lines that match the prefix
   */
  private static String findFirstMatchingLine(String data, String prefix) {
    if (data == null) {
      return "";
    }
    int ix = data.indexOf(prefix);
    if (ix >= 0) {
      int iy = data.indexOf("\n", ix);
      if (iy > 0) {
        return data.substring(ix, iy);
      }
    }
    return "";
  }

  private static String getParameterTypeName(Class cls) {
    String parameterTypeNameName = cls.getName();
    parameterTypeNameName = parameterTypeNameName.replace("[J", "[Xlong").replace("[I", "[Xint").replace("[Z", "[Xboolean").replace("[S", "[Xshort")
        .replace("[F", "[Xfloat").replace("[D", "[Xdouble").replace("[B", "[Xbyte").replace("[C", "[Xchar");
    int arrayNestingDepth = 0;
    int ix = parameterTypeNameName.indexOf("[");
    while (ix > -1) {
      arrayNestingDepth++;
      parameterTypeNameName = parameterTypeNameName.replaceFirst("(\\[\\w)|(\\[)", "");
      ix = parameterTypeNameName.indexOf("[");
    }
    parameterTypeNameName = parameterTypeNameName.replaceFirst(";", "");
    for (int k = 0; k < arrayNestingDepth; k++) {
      parameterTypeNameName = parameterTypeNameName + "[]";
    }
    return parameterTypeNameName;

  }
}