package daikon.config;

import java.io.InputStream;
import java.io.Serializable;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.checker.signature.qual.ClassGetName;
import org.plumelib.reflection.ReflectionPlume;
import org.plumelib.util.EntryReader;

/**
 * This class applies settings from a configuration file that lists variable names and values (see
 * "example-settings.txt" in this directory for an example). Multiple configuration files can be
 * read, and the results can be re-written to a new configuration file.
 *
 * <p>Important note: classes that have fields set via this Configuration (dkconfig) interface may
 * not reference daikon.Global in their static initializers, since Global loads the default
 * configuration, which classloads that class, and we would have a classloading circularity.
 */
public final class Configuration implements Serializable {
  /** If you add or remove fields, change this number to the current date. */
  static final long serialVersionUID = 20020122L;

  // ============================== REPRESENTATION ==============================

  /** The statements that set the configuration. */
  @SuppressWarnings("serial")
  private List<String> statements = new ArrayList<>();

  // ============================== STATIC COMPONENT ==============================

  static final String PREFIX = "dkconfig_";

  private static final Class<String> STRING_CLASS;

  static {
    try {
      @SuppressWarnings("unchecked")
      Class<String> STRING_CLASS_tmp = (Class<String>) Class.forName("java.lang.String");
      STRING_CLASS = STRING_CLASS_tmp;
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Returns the singleton instance of this class.
   *
   * @return the singleton instance of this class
   */
  public static Configuration getInstance() {
    return instance;
  }

  /** The singleton instance of this class. */
  private static volatile Configuration instance = new Configuration();

  /**
   * This used to read a file containing all of the configurable options so that when the options
   * were saved, they would reflect not only those options specified, but the default values as
   * well. This would guarantee that changes to the default options would be overridden by the file.
   *
   * <p>Unfortunately, that required maintaining a list of all of the configuration variables by
   * hand. This list quickly became out of date and it seemed that the random results were better
   * than no attempt at all. The file has thus been removed. If a configuration is changed it only
   * contains those items specified, not the default values of unspecified options.
   */
  private Configuration() {}

  /** Lets callers differentiate between configuration problems and all others. */
  public static class ConfigException extends RuntimeException {
    public ConfigException(String s, Throwable t) {
      super(s, t);
    }

    public ConfigException(String s) {
      super(s);
    }

    public ConfigException() {
      super();
    }

    // We are Serializable, so we specify a version to allow changes to
    // method signatures without breaking serialization.  If you add or
    // remove fields, you should change this number to the current date.
    static final long serialVersionUID = 20020130L;
  }

  // ============================== REPLAY ==============================

  public void replay() {
    // Make a copy of the statements, since apply mutates the list.
    List<String> copy = new ArrayList<>(statements);
    for (String statement : copy) {
      apply(statement);
    }
    statements = copy;
  }

  /**
   * Take the settings given in the argument and call this.apply(String) for each of them. This
   * essentially overlaps the settings given in the argument over this (appending them to this in
   * the process). This method is intended for loading a saved configuration from a file, since
   * calling this method with the Configuration singleton makes no sense.
   */
  public void overlap(Configuration config) {
    assert config != null;
    for (String statement : config.statements) {
      this.apply(statement);
    }
  }

  // ============================== ADT COMPONENT ==============================

  /**
   * Apply the settings in the given InputStream.
   *
   * @param input the commands to set confiuration
   */
  public void apply(InputStream input) {
    assert input != null;
    for (String line : new EntryReader(input)) {
      line = line.trim();
      if (line.length() == 0) continue; // skip blank lines
      if (line.charAt(0) == '#') continue; // skip # comment lines
      apply(line);
    }
  }

  /**
   * Apply the setting in the given InputStream.
   *
   * @param line the command to set confiuration
   */
  public void apply(String line) {
    assert line != null;

    int eq = line.indexOf('=');
    if (eq <= 0) {
      throw new ConfigException("Error, configuration setting must contain \"=\": " + line);
    }

    String name = line.substring(0, eq).trim();
    String value = line.substring(eq + 1).trim();

    apply(name, value);
  }

  /**
   * Set the given setting to the given value.
   *
   * @param name the setting to modify
   * @param value the setting's new value
   */
  public void apply(String name, String value) {
    assert name != null;
    assert value != null;

    int dot = name.lastIndexOf('.');
    if (dot == -1) {
      throw new daikon.Daikon.UserError(
          "Configuration option name must contain a period (.): " + name);
    }

    @SuppressWarnings("signature") // substring operation
    @ClassGetName String classname = name.substring(0, dot);
    String fieldname = name.substring(dot + 1);

    apply(classname, fieldname, value);
  }

  public void apply(@ClassGetName String classname, String fieldname, String value) {
    assert classname != null;
    assert fieldname != null;
    assert value != null;

    // Use ReflectionPlume version of class.forName so that we can refer to
    // inner classes using '.' as well as '$'
    Class<?> clazz;
    try {
      clazz = ReflectionPlume.classForName(classname);
    } catch (ClassNotFoundException e) {
      throw new ConfigException(
          String.format(
              "Configuration option %s=%s attempts to use nonexistent class %s",
              fieldname, value, classname),
          e);
    } catch (LinkageError e) {
      throw new ConfigException(
          String.format(
              "Configuration option %s=%s attempts to use class with linkage error %s",
              fieldname, value, classname),
          e);
    }

    apply(clazz, fieldname, value);
  }

  public void apply(Class<?> clazz, String fieldname, String value) {
    assert clazz != null;
    assert fieldname != null;
    assert value != null;

    Field field;
    try {
      field = clazz.getDeclaredField(PREFIX + fieldname);
    } catch (SecurityException e) {
      throw new ConfigException(
          "Configuration option " + clazz.getName() + "." + fieldname + " is inaccessible");
    } catch (NoSuchFieldException e) {
      throw new ConfigException(
          "Unknown configuration option " + clazz.getName() + "." + fieldname);
    }

    apply(field, value);
  }

  private void apply(Field field, String unparsed) {
    assert field != null;
    assert unparsed != null;

    Object value; // typed version of value
    Class<?> type = field.getType();

    if (type.equals(Boolean.TYPE)) {
      if (unparsed.equals("1") || unparsed.equalsIgnoreCase("true")) {
        value = Boolean.TRUE;
      } else if (unparsed.equals("0") || unparsed.equalsIgnoreCase("false")) {
        value = Boolean.FALSE;
      } else {
        throw new ConfigException(
            "Badly formatted boolean argument "
                + unparsed
                + " for configuration option "
                + field.getName());
      }
    } else if (type.equals(Integer.TYPE)) {
      try {
        // decode instead of valueOf to handle "0x" and other styles
        value = Integer.decode(unparsed);
      } catch (NumberFormatException e) {
        throw new ConfigException(
            "Badly formatted argument "
                + unparsed
                + " for configuration option "
                + field.getName());
      }
    } else if (type.equals(Long.TYPE)) {
      try {
        // decode instead of valueOf to handle "0x" and other styles
        value = Long.decode(unparsed);
      } catch (NumberFormatException e) {
        throw new ConfigException(
            "Badly formatted argument "
                + unparsed
                + " for configuration option "
                + field.getName());
      }
    } else if (type.equals(Float.TYPE)) {
      try {
        value = Float.valueOf(unparsed);
      } catch (NumberFormatException e) {
        throw new ConfigException(
            "Badly formatted argument "
                + unparsed
                + " for configuration option "
                + field.getName());
      }
    } else if (type.equals(Double.TYPE)) {
      // assert Double.class == Double.TYPE;
      try {
        value = Double.valueOf(unparsed);
      } catch (NumberFormatException e) {
        throw new ConfigException(
            "Badly formatted argument "
                + unparsed
                + " for configuration option "
                + field.getName());
      }
    } else if (type.equals(STRING_CLASS)) {
      value = unparsed;
      if ((unparsed.startsWith("\"") && unparsed.endsWith("\""))
          || (unparsed.startsWith("'") && unparsed.endsWith("'"))) {
        value = unparsed.substring(1, unparsed.length() - 1);
      }
      value = ((String) value).intern();
      // System.out.printf("setting %s to '%s'%n", field, value);
    } else if ((type.getSuperclass() != null)
        && type.getSuperclass().getName().equals("java.lang.Enum")) {
      try {
        java.lang.reflect.Method valueOf =
            type.getDeclaredMethod("valueOf", new Class<?>[] {STRING_CLASS});
        if (valueOf == null) {
          // Can't happen, so RuntimeException instead of ConfigException
          throw new RuntimeException("Didn't find valueOf in " + type);
        }
        try {
          @SuppressWarnings("nullness") // static method, so null first arg is OK: valueOf()
          Object tmp_value = valueOf.invoke(null, unparsed);
          value = tmp_value;
        } catch (IllegalArgumentException e) {
          throw new ConfigException(
              "Badly formatted argument "
                  + unparsed
                  + " for configuration option "
                  + field.getName()
                  + ": "
                  + e.getMessage());
        }
      } catch (NoSuchMethodException e) {
        // Can't happen, so RuntimeException instead of ConfigException
        throw new RuntimeException(e);
      } catch (IllegalAccessException e) {
        // Can't happen, so RuntimeException instead of ConfigException
        throw new RuntimeException(e);
      } catch (java.lang.reflect.InvocationTargetException e) {
        // Can't happen, so RuntimeException instead of ConfigException
        throw new RuntimeException(e);
      }
    } else {
      throw new ConfigException(
          "Internal error: Unsupported type "
              + type.getName()
              + " for configuration option "
              + field.toString());
    }

    try {
      setStaticField(field, value);
    } catch (IllegalAccessException e) {
      throw new ConfigException("Inaccessible configuration option " + field.toString());
    }

    // record the application
    String classname = field.getDeclaringClass().getName();
    String fieldname = field.getName();
    assert fieldname.startsWith(PREFIX); // remove the prefix
    fieldname = fieldname.substring(PREFIX.length());
    addRecord(classname, fieldname, unparsed);
  }

  private void addRecord(String classname, String fieldname, String unparsed) {
    assert !fieldname.startsWith(PREFIX); // must not have prefix
    String record = classname + "." + fieldname + " = " + unparsed;
    statements.add(record);
  }

  /**
   * Set a static field to the given value.
   *
   * @param field a field; must be static
   * @param value the value to set the field to
   * @throws IllegalAccessException if {@code field} is enforcing Java language access control and
   *     the underlying field is either inaccessible or final.
   */
  // This method exists to reduce the scope of the warning suppression.
  @SuppressWarnings({
    "nullness:argument", // field is static, so object may be null
    "interning:argument" // interning is not necessary for how this method is used
  })
  private static void setStaticField(Field field, @Nullable Object value)
      throws IllegalAccessException {
    field.set(null, value);
  }
}