package org.kuali.common.util.spring.env;

import java.io.File;
import java.util.Properties;

import org.kuali.common.util.Assert;
import org.kuali.common.util.ModeUtils;
import org.kuali.common.util.spring.env.model.EnvironmentServiceContext;

/**
 * <p>
 * By default, an exception is thrown if a value cannot be located (unless a default value has been supplied).
 * </p>
 * 
 * <p>
 * By default, an exception is thrown if any placeholders cannot be resolved in any string values.
 * </p>
 * 
 * <p>
 * By default, string values are resolved before being returned
 * </p>
 * 
 * <p>
 * By default, environment variables are automatically checked if a normal property value cannot be found.
 * 
 * For example, given the key <code>db.vendor</code> the service will also automatically check <code>env.DB_VENDOR</code>
 * </p>
 */
public final class BasicEnvironmentService implements EnvironmentService {

        private final EnvironmentServiceContext context;

        /**
         * Uses system properties / environment variables to resolve values
         */
        public BasicEnvironmentService() {
                this(new EnvironmentServiceContext.Builder().build());
        }

        /**
         * Uses <code>properties</code> to resolve values
         */
        public BasicEnvironmentService(Properties properties) {
                this(new EnvironmentServiceContext.Builder().env(properties).build());
        }

        /**
         * Uses <code>context</code> to resolve values
         */
        public BasicEnvironmentService(EnvironmentServiceContext context) {
                Assert.noNulls(context);
                this.context = context;
        }

        @Override
        public boolean containsProperty(String key) {
                Assert.noBlanks(key);
                return context.getEnv().containsProperty(key);
        }

        @Override
        public <T> T getProperty(EnvContext<T> context) {

                // If context is null, we have issues
                Assert.noNulls(context);

                // Extract a value from Spring's Environment abstraction
                T springValue = getSpringValue(context.getKey(), context.getType());

                // If that value is null, use whatever default value they gave us (this might also be null)
                T returnValue = (springValue == null) ? context.getDefaultValue() : springValue;

                // If we could not locate a value, we may need to error out
                if (returnValue == null) {
                        ModeUtils.validate(this.context.getMissingPropertyMode(), getMissingPropertyMessage(context.getKey()));
                }

                // Return the value we've located
                return returnValue;
        }

        @Override
        public <T> T getProperty(String key, Class<T> type, T provided) {
                return getProperty(EnvContext.newCtx(key, type, provided));
        }

        @Override
        public <T> T getProperty(String key, Class<T> type) {
                return getProperty(EnvContext.newCtx(key, type, null));
        }

        protected String getMissingPropertyMessage(String key) {
                if (context.isCheckEnvironmentVariables()) {
                        String envKey = EnvUtils.getEnvironmentVariableKey(key);
                        return "No value for [" + key + "] or [" + envKey + "]";
                } else {
                        return "No value for [" + key + "]";
                }
        }

        protected <T> T getSpringValue(String key, Class<T> type) {
                T value = context.getEnv().getProperty(key, type);
                if (value == null && context.isCheckEnvironmentVariables()) {
                        String envKey = EnvUtils.getEnvironmentVariableKey(key);
                        return context.getEnv().getProperty(envKey, type);
                } else {
                        return value;
                }
        }

        protected <T> Class<T> getSpringValueAsClass(String key, Class<T> type) {
                Class<T> value = context.getEnv().getPropertyAsClass(key, type);
                if (value == null && context.isCheckEnvironmentVariables()) {
                        String envKey = EnvUtils.getEnvironmentVariableKey(key);
                        return context.getEnv().getPropertyAsClass(envKey, type);
                } else {
                        return value;
                }
        }

        @Override
        public <T> Class<T> getClass(String key, Class<T> type) {
                return getClass(key, type, null);
        }

        @Override
        public <T> Class<T> getClass(String key, Class<T> type, Class<T> defaultValue) {
                Class<T> springValue = getSpringValueAsClass(key, type);
                Class<T> returnValue = (springValue == null) ? defaultValue : springValue;

                // If we could not locate a value, we may need to error out
                if (returnValue == null) {
                        ModeUtils.validate(context.getMissingPropertyMode(), getMissingPropertyMessage(key));
                }

                // Return what we've got
                return returnValue;
        }

        @Override
        public String getString(String key) {
                return getString(key, null);
        }

        @Override
        public String getString(String key, String defaultValue) {
                String string = getProperty(EnvContext.newString(key, defaultValue));
                if (context.isResolveStrings()) {
                        return context.getEnv().resolveRequiredPlaceholders(string);
                } else {
                        return string;
                }
        }

        @Override
        public Boolean getBoolean(String key) {
                return getBoolean(key, null);
        }

        @Override
        public Boolean getBoolean(String key, Boolean defaultValue) {
                return getProperty(EnvContext.newBoolean(key, defaultValue));
        }

        @Override
        public File getFile(String key) {
                return getFile(key, null);
        }

        @Override
        public File getFile(String key, File defaultValue) {
                return getProperty(EnvContext.newFile(key, defaultValue));
        }

        @Override
        public Integer getInteger(String key, Integer defaultValue) {
                return getProperty(EnvContext.newInteger(key, defaultValue));
        }

        @Override
        public Integer getInteger(String key) {
                return getInteger(key, null);
        }

        public EnvironmentServiceContext getContext() {
                return context;
        }

}