package org.unix4j.unix.head;

import java.util.List;
import java.util.Map;
import java.util.Arrays;

import org.unix4j.command.Arguments;
import org.unix4j.context.ExecutionContext;
import org.unix4j.convert.ValueConverter;
import org.unix4j.option.DefaultOptionSet;
import org.unix4j.util.ArgsUtil;
import org.unix4j.util.ArrayUtil;
import org.unix4j.variable.Arg;
import org.unix4j.variable.VariableContext;

import org.unix4j.unix.Head;

/**
 * Arguments and options for the {@link Head head} command.
 */
public final class HeadArguments implements Arguments<HeadArguments> {
        
        private final HeadOptions options;

        
        // operand: <count>
        private long count;
        private boolean countIsSet = false;
        
        // operand: <paths>
        private String[] paths;
        private boolean pathsIsSet = false;
        
        // operand: <files>
        private java.io.File[] files;
        private boolean filesIsSet = false;
        
        // operand: <args>
        private String[] args;
        private boolean argsIsSet = false;
        
        /**
         * Constructor to use if no options are specified.
         */
        public HeadArguments() {
                this.options = HeadOptions.EMPTY;
        }

        /**
         * Constructor with option set containing the selected command options.
         * 
         * @param options the selected options
         * @throws NullPointerException if the argument is null
         */
        public HeadArguments(HeadOptions options) {
                if (options == null) {
                        throw new NullPointerException("options argument cannot be null");
                }
                this.options = options;
        }
        
        /**
         * Returns the options set containing the selected command options. Returns
         * an empty options set if no option has been selected.
         * 
         * @return set with the selected options
         */
        public HeadOptions getOptions() {
                return options;
        }

        /**
         * Constructor string arguments encoding options and arguments, possibly
         * also containing variable expressions. 
         * 
         * @param args string arguments for the command
         * @throws NullPointerException if args is null
         */
        public HeadArguments(String... args) {
                this();
                this.args = args;
                this.argsIsSet = true;
        }
        private Object[] resolveVariables(VariableContext context, String... unresolved) {
                final Object[] resolved = new Object[unresolved.length];
                for (int i = 0; i < resolved.length; i++) {
                        final String expression = unresolved[i];
                        if (Arg.isVariable(expression)) {
                                resolved[i] = resolveVariable(context, expression);
                        } else {
                                resolved[i] = expression;
                        }
                }
                return resolved;
        }
        private <V> V convertList(ExecutionContext context, String operandName, Class<V> operandType, List<Object> values) {
                if (values.size() == 1) {
                        final Object value = values.get(0);
                        return convert(context, operandName, operandType, value);
                }
                return convert(context, operandName, operandType, values);
        }

        private Object resolveVariable(VariableContext context, String variable) {
                final Object value = context.getValue(variable);
                if (value != null) {
                        return value;
                }
                throw new IllegalArgumentException("cannot resolve variable " + variable + 
                                " in command: head " + this);
        }
        private <V> V convert(ExecutionContext context, String operandName, Class<V> operandType, Object value) {
                final ValueConverter<V> converter = context.getValueConverterFor(operandType);
                final V convertedValue;
                if (converter != null) {
                        convertedValue = converter.convert(value);
                } else {
                        if (HeadOptions.class.equals(operandType)) {
                                convertedValue = operandType.cast(HeadOptions.CONVERTER.convert(value));
                        } else {
                                convertedValue = null;
                        }
                }
                if (convertedValue != null) {
                        return convertedValue;
                }
                throw new IllegalArgumentException("cannot convert --" + operandName + 
                                " value '" + value + "' into the type " + operandType.getName() + 
                                " for head command");
        }
        
        @Override
        public HeadArguments getForContext(ExecutionContext context) {
                if (context == null) {
                        throw new NullPointerException("context cannot be null");
                }
                if (!argsIsSet || args.length == 0) {
                        //nothing to resolve
                        return this;
                }

                //check if there is at least one variable
                boolean hasVariable = false;
                for (final String arg : args) {
                        if (arg != null && arg.startsWith("$")) {
                                hasVariable = true;
                                break;
                        }
                }
                //resolve variables
                final Object[] resolvedArgs = hasVariable ? resolveVariables(context.getVariableContext(), this.args) : this.args;
                
                //convert now
                final List<String> defaultOperands = Arrays.asList("paths");
                final Map<String, List<Object>> map = ArgsUtil.parseArgs("options", defaultOperands, resolvedArgs);
                final HeadOptions.Default options = new HeadOptions.Default();
                final HeadArguments argsForContext = new HeadArguments(options);
                for (final Map.Entry<String, List<Object>> e : map.entrySet()) {
                        if ("count".equals(e.getKey())) {
                                        
                                final long value = convertList(context, "count", long.class, e.getValue());  
                                argsForContext.setCount(value);
                        } else if ("paths".equals(e.getKey())) {
                                        
                                final String[] value = convertList(context, "paths", String[].class, e.getValue());  
                                argsForContext.setPaths(value);
                        } else if ("files".equals(e.getKey())) {
                                        
                                final java.io.File[] value = convertList(context, "files", java.io.File[].class, e.getValue());  
                                argsForContext.setFiles(value);
                        } else if ("args".equals(e.getKey())) {
                                throw new IllegalStateException("invalid operand '" + e.getKey() + "' in head command args: " + Arrays.toString(args));
                        } else if ("options".equals(e.getKey())) {
                                        
                                final HeadOptions value = convertList(context, "options", HeadOptions.class, e.getValue());  
                                options.setAll(value);
                        } else {
                                throw new IllegalStateException("invalid operand '" + e.getKey() + "' in head command args: " + Arrays.toString(args));
                        }
                }
                return argsForContext;
        }
        
        /**
         * Returns the {@code <count>} operand value: The first {@code count} lines of each input file are
                        copied to standard output, starting from 1 (characters instead of 
                        lines if the {@code -c} option is specified). Must be a non-negative 
                        integer or an exception is thrown. If {@code count} is greater than 
                        the number number of lines (characters) in the input, the
                        application will not error and send the whole file to the output.
         * 
         * @return the {@code <count>} operand value (variables are not resolved)
         * @throws IllegalStateException if this operand has never been set
         * 
         */
        public long getCount() {
                if (countIsSet) {
                        return count;
                }
                throw new IllegalStateException("operand has not been set: " + count);
        }

        /**
         * Returns true if the {@code <count>} operand has been set. 
         * <p>
         * Note that this method returns true even if {@code null} was passed to the
         * {@link #setCount(long)} method.
         * 
         * @return      true if the setter for the {@code <count>} operand has 
         *                      been called at least once
         */
        public boolean isCountSet() {
                return countIsSet;
        }
        /**
         * Sets {@code <count>}: The first {@code count} lines of each input file are
                        copied to standard output, starting from 1 (characters instead of 
                        lines if the {@code -c} option is specified). Must be a non-negative 
                        integer or an exception is thrown. If {@code count} is greater than 
                        the number number of lines (characters) in the input, the
                        application will not error and send the whole file to the output.
         * 
         * @param count the value for the {@code <count>} operand
         */
        public void setCount(long count) {
                this.count = count;
                this.countIsSet = true;
        }
        /**
         * Returns the {@code <paths>} operand value: Pathnames of the input files to be filtered; wildcards * and ? are 
                        supported; relative paths are resolved on the basis of the current 
                        working directory.
         * 
         * @return the {@code <paths>} operand value (variables are not resolved)
         * @throws IllegalStateException if this operand has never been set
         * 
         */
        public String[] getPaths() {
                if (pathsIsSet) {
                        return paths;
                }
                throw new IllegalStateException("operand has not been set: " + paths);
        }

        /**
         * Returns true if the {@code <paths>} operand has been set. 
         * <p>
         * Note that this method returns true even if {@code null} was passed to the
         * {@link #setPaths(String[])} method.
         * 
         * @return      true if the setter for the {@code <paths>} operand has 
         *                      been called at least once
         */
        public boolean isPathsSet() {
                return pathsIsSet;
        }
        /**
         * Sets {@code <paths>}: Pathnames of the input files to be filtered; wildcards * and ? are 
                        supported; relative paths are resolved on the basis of the current 
                        working directory.
         * 
         * @param paths the value for the {@code <paths>} operand
         */
        public void setPaths(String... paths) {
                this.paths = paths;
                this.pathsIsSet = true;
        }
        /**
         * Returns the {@code <files>} operand value: The input files to be filtered; relative paths are not resolved (use 
                        the string paths argument to enable relative path resolving based on 
                        the current working directory).
         * 
         * @return the {@code <files>} operand value (variables are not resolved)
         * @throws IllegalStateException if this operand has never been set
         * 
         */
        public java.io.File[] getFiles() {
                if (filesIsSet) {
                        return files;
                }
                throw new IllegalStateException("operand has not been set: " + files);
        }

        /**
         * Returns true if the {@code <files>} operand has been set. 
         * <p>
         * Note that this method returns true even if {@code null} was passed to the
         * {@link #setFiles(java.io.File[])} method.
         * 
         * @return      true if the setter for the {@code <files>} operand has 
         *                      been called at least once
         */
        public boolean isFilesSet() {
                return filesIsSet;
        }
        /**
         * Sets {@code <files>}: The input files to be filtered; relative paths are not resolved (use 
                        the string paths argument to enable relative path resolving based on 
                        the current working directory).
         * 
         * @param files the value for the {@code <files>} operand
         */
        public void setFiles(java.io.File... files) {
                this.files = files;
                this.filesIsSet = true;
        }
        /**
         * Returns the {@code <args>} operand value: String arguments defining the options and operands for the command. 
                        Options can be specified by acronym (with a leading dash "-") or by 
                        long name (with two leading dashes "--"). Operands other than the
                        default "--paths" operand have to be prefixed with the operand 
                        name (e.g. "--count" for a subsequent count operand value).
         * 
         * @return the {@code <args>} operand value (variables are not resolved)
         * @throws IllegalStateException if this operand has never been set
         * 
         */
        public String[] getArgs() {
                if (argsIsSet) {
                        return args;
                }
                throw new IllegalStateException("operand has not been set: " + args);
        }

        /**
         * Returns true if the {@code <args>} operand has been set. 
         * 
         * @return      true if the setter for the {@code <args>} operand has 
         *                      been called at least once
         */
        public boolean isArgsSet() {
                return argsIsSet;
        }
        
        /**
         * Returns true if the {@code --}{@link HeadOption#chars chars} option
         * is set. The option is also known as {@code -}c option.
         * <p>
         * Description: The {@code count} argument is in units of characters instead of 
                        lines. Starts from 1 and includes line ending characters.
         * 
         * @return true if the {@code --chars} or {@code -c} option is set
         */
        public boolean isChars() {
                return getOptions().isSet(HeadOption.chars);
        }
        /**
         * Returns true if the {@code --}{@link HeadOption#suppressHeaders suppressHeaders} option
         * is set. The option is also known as {@code -}q option.
         * <p>
         * Description: Suppresses printing of headers when multiple files are being
                        examined.
         * 
         * @return true if the {@code --suppressHeaders} or {@code -q} option is set
         */
        public boolean isSuppressHeaders() {
                return getOptions().isSet(HeadOption.suppressHeaders);
        }

        @Override
        public String toString() {
                // ok, we have options or arguments or both
                final StringBuilder sb = new StringBuilder();

                if (argsIsSet) {
                        for (String arg : args) {
                                if (sb.length() > 0) sb.append(' ');
                                sb.append(arg);
                        }
                } else {
                
                        // first the options
                        if (options.size() > 0) {
                                sb.append(DefaultOptionSet.toString(options));
                        }
                        // operand: <count>
                        if (countIsSet) {
                                if (sb.length() > 0) sb.append(' ');
                                sb.append("--").append("count");
                                sb.append(" ").append(toString(getCount()));
                        }
                        // operand: <paths>
                        if (pathsIsSet) {
                                if (sb.length() > 0) sb.append(' ');
                                sb.append("--").append("paths");
                                sb.append(" ").append(toString(getPaths()));
                        }
                        // operand: <files>
                        if (filesIsSet) {
                                if (sb.length() > 0) sb.append(' ');
                                sb.append("--").append("files");
                                sb.append(" ").append(toString(getFiles()));
                        }
                        // operand: <args>
                        if (argsIsSet) {
                                if (sb.length() > 0) sb.append(' ');
                                sb.append("--").append("args");
                                sb.append(" ").append(toString(getArgs()));
                        }
                }
                
                return sb.toString();
        }
        private static String toString(Object value) {
                if (value != null && value.getClass().isArray()) {
                        return ArrayUtil.toString(value);
                }
                return String.valueOf(value);
        }
}