task 1 done

README.md

@@ -0,0 +1,28 @@
+# au_software_design
+
+##1. Shell
+
+###Command line utility similar to Unix shell.
+
+####Supported features:
+
+* echo command
+* cat command
+* wc command
+* exit command
+* pwd command
+* environment variables 
+* unknown commands are passed to system shell as separate process through Java.Process library.
+
+####Class diagram:
+![shell class diagram](https://www.gliffy.com/go/share/image/smx5dub0j39jxied850w.png?utm_medium=live-embed&utm_source=custom)
+
+####Data flow:
+  * Main: run Shell object.
+  * Shell: Read line from System.in.
+
+   * Preprocessor: Substitute environment variables in input string. E. g. "Hello, $name" -> "Hello, Alex"
+   * Tokeniser: Split string into a list of tokens: words and operators.
+   * Parser: Parse list of tokens as sequence of commands divided by pipes.
+   * Command Executor: Perform chained computation passing output of one comand as input to the next one.
+   * Pass result to System.in and loop again.

shell/build.gradle

@@ -2,13 +2,19 @@ group 'simiyutin'
 version '1.0-SNAPSHOT'
 
 apply plugin: 'java'
+apply plugin: 'application'
+mainClassName = "com.simiyutin.au.shell.core.Main"
 
 sourceCompatibility = 1.8
 
 repositories {
     mavenCentral()
 }
 
+run{
+    standardInput = System.in
+}
+
 dependencies {
     testCompile group: 'junit', name: 'junit', version: '4.11'
 }

shell/src/main/java/com/simiyutin/au/shell/commands/Cat.java

@@ -0,0 +1,54 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.io.IOException;
+import java.nio.charset.MalformedInputException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.Scanner;
+
+/**
+ * Reads file from parameter to stdout or reflects stdin to stdout
+ */
+public class Cat extends Command {
+
+    public static final String NAME = "cat";
+
+    public Cat(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream stream) throws CommandExecutionException {
+
+        if (stream.hasNext()) {
+            return stream;
+        }
+
+        Stream res = new Stream();
+        if (args.isEmpty()) {
+            Scanner sc = new Scanner(System.in);
+            while (true) {
+                System.out.println(sc.nextLine());
+            }
+        } else {
+            String filename = args.get(0);
+            Path file = Paths.get(filename);
+            try {
+                List<String> lines = Files.readAllLines(file);
+                lines.forEach(res::write);
+            } catch (MalformedInputException e) {
+                throw new CommandExecutionException("Cannot determine file encoding");
+            } catch (IOException e) {
+                throw new CommandExecutionException("Error while reading file: " + e.toString());
+            }
+        }
+        return res;
+    }
+}

shell/src/main/java/com/simiyutin/au/shell/commands/Echo.java

@@ -0,0 +1,33 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+
+/**
+ * Prints arguments to output stream
+ */
+public class Echo extends Command {
+
+    public static final String NAME = "echo";
+
+    public Echo(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream ignored) throws CommandExecutionException {
+
+        String toPrint = args.stream().collect(Collectors.joining());
+
+        Stream stream = new Stream();
+        stream.write(toPrint);
+        return stream;
+    }
+
+}

shell/src/main/java/com/simiyutin/au/shell/commands/Eq.java

@@ -0,0 +1,26 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.util.List;
+
+/**
+ * Puts new variable in context or changes variable value
+ */
+public class Eq extends Command {
+
+    public Eq(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream ignored) throws CommandExecutionException {
+        String var = args.get(0);
+        String val = args.get(1);
+        env.put(var, val);
+        return new Stream();
+    }
+}

shell/src/main/java/com/simiyutin/au/shell/commands/Exit.java

@@ -0,0 +1,26 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.util.List;
+
+/**
+ * Exits shell
+ */
+public class Exit extends Command {
+
+    public static final String NAME = "exit";
+
+    public Exit(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream stream) throws CommandExecutionException {
+        System.exit(0);
+        return null;
+    }
+}

shell/src/main/java/com/simiyutin/au/shell/commands/OutSource.java

@@ -0,0 +1,59 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.io.*;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Passes input arguments and stream to external shell and reads result from its stdout
+ */
+public class OutSource extends Command {
+
+    private String commandName;
+
+    public OutSource(String commandName, List<String> args, Environment env) {
+        super(args, env);
+        this.commandName = commandName;
+    }
+
+    @Override
+    public Stream run(Stream stream) throws CommandExecutionException {
+        String command = commandName + " " + args.stream().collect(Collectors.joining(" "));
+        Stream output = new Stream();
+        try {
+            Process process = Runtime.getRuntime().exec(command);
+            write(process, stream);
+            output = read(process);
+        } catch (IOException | InterruptedException e) {
+            throw new CommandExecutionException("System error: " + e.toString());
+        }
+        return output;
+    }
+
+    private void write(Process process, Stream stream) throws IOException {
+        Writer handle = new PrintWriter(process.getOutputStream());
+        final int lineFeed = 10;
+        while (stream.hasNext()) {
+            handle.write(stream.read());
+            handle.write(lineFeed);
+        }
+        handle.close();
+    }
+
+    private Stream read(Process process) throws IOException, InterruptedException {
+        Stream output = new Stream();
+        BufferedReader reader =
+                new BufferedReader(new InputStreamReader(process.getInputStream()));
+        String line;
+        while ((line = reader.readLine()) != null) {
+            output.write(line);
+        }
+        process.waitFor();
+        return output;
+    }
+}

shell/src/main/java/com/simiyutin/au/shell/commands/Pwd.java

@@ -0,0 +1,31 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+
+/**
+ * Prints current directory
+ */
+public class Pwd extends Command {
+
+    public static final String NAME = "pwd";
+
+    public Pwd(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream ignored) throws CommandExecutionException {
+        Path currentRelativePath = Paths.get("");
+        String currentDir = currentRelativePath.toAbsolutePath().toString();
+        Stream stream = new Stream();
+        stream.write(currentDir);
+        return stream;
+    }
+}

shell/src/main/java/com/simiyutin/au/shell/commands/Wc.java

@@ -0,0 +1,88 @@
+package com.simiyutin.au.shell.commands;
+
+import com.simiyutin.au.shell.core.exceptions.CommandExecutionException;
+import com.simiyutin.au.shell.core.Command;
+import com.simiyutin.au.shell.core.Environment;
+import com.simiyutin.au.shell.core.Stream;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Collectors;
+
+/**
+ * Counts lines, words and bytes in given file or input stream
+ */
+public class Wc extends Command {
+
+    public static final String NAME = "wc";
+
+    public Wc(List<String> args, Environment env) {
+        super(args, env);
+    }
+
+    @Override
+    public Stream run(Stream stream) throws CommandExecutionException {
+        if (!args.isEmpty()) {
+            return handleFile();
+        } else if (stream.hasNext()) {
+            return handleInputStream(stream);
+        } else {
+            handleStdIn();
+            return new Stream();
+        }
+    }
+
+    private Stream handleFile() {
+        String fileName = args.get(0);
+        Path file = Paths.get(fileName);
+        try {
+            List<String> lines = Files.readAllLines(file);
+            return parseLines(lines);
+        } catch (IOException e) {
+            e.printStackTrace();
+            return new Stream();
+        }
+    }
+
+    private Stream handleInputStream(Stream stream) {
+        List<String> lines = new ArrayList<>();
+        while (stream.hasNext()) {
+            lines.add(stream.read());
+        }
+        return parseLines(lines);
+    }
+
+    private void handleStdIn() {
+        Scanner sc = new Scanner(System.in);
+        while (true) {
+            List<String> lines = Collections.singletonList(sc.nextLine());
+            Stream result = parseLines(lines);
+            System.out.println(result.read());
+        }
+    }
+
+    private Stream parseLines(List<String> lines) {
+        int linesCount = lines.size();
+        char[] concatenated = lines.stream().collect(Collectors.joining(" ")).toCharArray();
+        long wordCount = 0;
+        for (char c : concatenated) {
+            if (c == ' ') {
+                wordCount++;
+            }
+        }
+        wordCount++;
+
+        long byteCount = concatenated.length;
+
+        String result = String.format("    %d    %d    %d", linesCount, wordCount, byteCount);
+        Stream stream = new Stream();
+        stream.write(result);
+        return stream;
+    }
+}