Implementing a new Stack type

server/server/errors.go

@@ -2,25 +2,39 @@ package server
 
 import "errors"
 
-// InputError will be raised when the input is not right.
+// InputError will be raised when the input given to the parser by the client is not right.
 type InputError struct {
 	// The operation that caused the error.
-	Op  string
+	Op string
 	// The error that occurred during the operation.
 	Err error
 }
 
-func (e *InputError) Error() string { return "Error: " + e.Op + ": " + e.Err.Error() }
+func (e InputError) Error() string { return "Error: " + e.Op + ": " + e.Err.Error() }
 
 // Input Errors
 var (
-	UnknownError     = errors.New("Unknown Error.")
+	InputUnknownError     = errors.New("Unknown Error.")
-	InvalidCommand   = errors.New("Invalid command.")
+	InputInvalidCommand   = errors.New("Invalid command.")
-	TooManyArguments = errors.New("Too many arguments.")
+	InputTooManyArguments = errors.New("Too many arguments.")
-	TooFewArguments  = errors.New("Too few arguments.")
+	InputTooFewArguments  = errors.New("Too few arguments.")
 )
 
-// Command Errors
+// Command Errors represent errors that occur when the server is executing commands
 var (
 	GetNoBitsError = errors.New("The file/directory contains zero bits!")
-)
+)
+
+type StackError struct {
+	ErrorName string
+	Err       error
+}
+
+func (e StackError) Error() string { return e.ErrorName + ": " + e.Err.Error() }
+
+// Stack Errors
+var (
+	StackInvalidTypeError = StackError{"InvalidTypeError", errors.New("Invalid item type for the Stack")}
+	StackOverflowError    = StackError{"StackOverflowError", errors.New("Stack capacity exceeded!")}
+	StackUnderflowError    = StackError{"StackUnderflowError", errors.New("Stack is empty!")}
+)

server/server/parser.go

@@ -8,9 +8,9 @@ import (
 // checkArgumentsLength returns an error if length is not equal to expected.
 func checkArgumentsLength(length int, expected int) error {
 	if length > expected {
-		return TooManyArguments
+		return InputTooManyArguments
 	} else if length < expected {
-		return TooFewArguments
+		return InputTooFewArguments
 	}
 	return nil
 }
@@ -81,7 +81,7 @@ func ProcessInput(c net.Conn, text string) error {
 
 		c.Close()
 	default:
-		return &InputError{thisCommand, InvalidCommand}
+		return &InputError{thisCommand, InputInvalidCommand}
 	}
 
 	return nil

server/server/stack.go

@@ -0,0 +1,77 @@
+package server
+
+// Stack interface
+type Stack interface {
+	// Push pushes an item to the stack. Returns an error if it fails.
+	Push(item interface{})
+	// Pop retrieves an item from the stack and removes it.
+	Pop() interface{}
+	// Top peeks at an item from the stack.
+	Top() interface{}
+	// IsEmpty returns bool indicating if the stack is empty.
+	IsEmpty() bool
+	// Capacity returns the capacity of the stack.
+	Capacity() int
+	// Size returns the size of the stack
+	Size() int
+}
+
+// StringStack is a stack that holds string objects
+type StringStack struct {
+	index    int
+	capacity int
+	items    []string
+}
+
+func MakeStringStack(capacity int) *StringStack {
+	st := StringStack{}
+
+	st.capacity = capacity
+	st.index = 0
+	st.items = make([]string, capacity, capacity)
+
+	return &st
+}
+
+func (st *StringStack) Push(item interface{}) {
+	if st.index == st.Capacity() {
+		panic(StackOverflowError)
+	}
+
+	value, ok := item.(string)
+
+	if ok == false {
+		panic(StackInvalidTypeError)
+	}
+
+	st.items[st.index] = value
+	st.index++
+
+}
+
+func (st *StringStack) Pop() interface{} {
+	if st.Size() == 0 {
+		panic(StackUnderflowError)
+	}
+	st.index--
+	return st.items[st.index]
+}
+
+func (st *StringStack) Top() interface{} {
+	if st.Size() == 0 {
+		panic(StackUnderflowError)
+	}
+	return st.items[st.index-1]
+}
+
+func (st *StringStack) IsEmpty() bool {
+	return st.Size() == 0
+}
+
+func (st *StringStack) Capacity() int {
+	return st.capacity
+}
+
+func (st *StringStack) Size() int {
+	return st.index
+}

server/server/stack_test.go

@@ -0,0 +1,159 @@
+package server
+
+import (
+	"testing"
+	"math/rand"
+)
+
+func TestMakeStringStack(t *testing.T) {
+	st := MakeStringStack(10)
+
+	if st == nil {
+		t.Errorf("MakeStringStack returned null!")
+	}
+
+	if st.Capacity() != 10 {
+		t.Errorf("StringStack: Stack capacity is not ok! Want: 10 Got: %d", st.Capacity())
+	}
+
+	if st.IsEmpty() != true {
+		t.Errorf("StringStack: Newly created stack is not empty!")
+	}
+}
+
+func TestStringStack_CanPush(t *testing.T) {
+	var st Stack = MakeStringStack(10)
+
+	str := "Hello World"
+
+	st.Push(str)
+
+	if st.Top() != str {
+		t.Errorf("StringStack: Push() failed. Want: %s Got: %s", str, st.Top())
+	}
+
+	if st.Size() != 1 {
+		t.Errorf("StringStack: Size is not correct after one push. Want %d Got %d", 1, st.Size())
+	}
+}
+
+func TestStringStack_StackOverflows(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("StringStack: Capacity of 0 doesn't overflow on Push()!")
+		}
+	}()
+
+	st := MakeStringStack(0)
+	st.Push(".")
+}
+
+func TestStringStack_InvalidType(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("StringStack: Push() pushed a non-string type.")
+		}
+	}()
+
+	st := MakeStringStack(1)
+	st.Push(1)
+}
+
+func TestStringStack_Capacity(t *testing.T) {
+	stCap := rand.Intn(100)
+	st := MakeStringStack(stCap)
+
+	if st.Capacity() != stCap {
+		t.Errorf("StringStack: Invalid capacity! Want: %d Got: %d", stCap, st.Capacity())
+	}
+}
+
+func TestStringStack_Size(t *testing.T) {
+	pushes := rand.Intn(10)
+	st := MakeStringStack(15)
+
+	for i := 0; i < pushes; i++ {
+		st.Push("a")
+	}
+
+	if st.Size() != pushes {
+		t.Errorf("StringStack: Invalid size! Want: %d Got %d", pushes, st.Size())
+	}
+}
+
+func TestStringStack_IsEmpty(t *testing.T) {
+	st := MakeStringStack(10)
+
+	if st.IsEmpty() == false {
+		t.Errorf("StringStack: With no push, the stack is not empty!")
+	}
+}
+
+func TestStringStack_IsEmptyAfterPushAndPop(t *testing.T) {
+	st := MakeStringStack(10)
+	pushes := rand.Intn(5)
+
+	for i := 0; i < pushes; i++ {
+		st.Push("a")
+	}
+
+	for i := 0; i < pushes; i++ {
+		st.Pop()
+	}
+
+	if st.IsEmpty() == false {
+		t.Errorf("StringStack: After push and pop, the stack is not empty!")
+	}
+}
+
+func TestStringStack_Top(t *testing.T) {
+	st := MakeStringStack(1)
+
+	st.Push("A")
+
+	if st.Top() != "A" {
+		t.Errorf("StringStack: Top() returned invalid value!")
+	}
+}
+
+func TestStringStack_TopUnderflow(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("StringStack: Top() on empty stack didn't underflow.")
+		}
+	}()
+
+	st := MakeStringStack(1)
+	st.Top()
+}
+
+func TestStringStack_Pop(t *testing.T) {
+	st := MakeStringStack(1)
+
+	st.Push("A")
+
+	if st.Pop() != "A" {
+		t.Errorf("StringStack: Pop() returned invalid value!")
+	}
+}
+
+func TestStringStack_Push(t *testing.T) {
+	st := MakeStringStack(1)
+	st.Push("A")
+}
+
+func TestStringStack_PushAndPop(t *testing.T) {
+	st := MakeStringStack(12)
+	characters := []string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"}
+	pushes := rand.Intn(len(characters))
+
+	for i := 0; i < pushes; i++ {
+		st.Push(characters[i])
+	}
+
+	for i := pushes - 1; i >= 0; i-- {
+		if val := st.Pop(); val != characters[i] {
+			t.Errorf("StringStack: Pop() and Push() don't work correctly. Want %s Got %s", characters[i], val)
+		}
+	}
+}