Managing Document Editing History using Stacks in Go

Introduction

Welcome! Today, we will delve into managing a document's editing history using stacks . Imagine building a text editor; you would need to handle actions like adding text, undoing, and redoing those changes. We will see how these features can be efficiently implemented using stacks. By the end of this lesson, you will possess an in-depth understanding of applying stacks in practical scenarios.

Introducing Methods to Implement

Before starting the coding portion, let's dissect the functions we will implement. These functions will manage a document's edit history, allowing us to apply changes, undo them, and redo them effectively. func (d *DocumentHistory) ApplyChange(change string) : This function applies a change to the document. The change, represented as a string, is stored in a way that allows us to remember the order of applied changes. Any previously undone changes are discarded. func (d *DocumentHistory) Undo() (string, bool) : This function undoes the most recent change and allows us to store it for a possible redo. It returns the change that was undone and a boolean indicating success. If there are no changes available to undo, it returns an empty string and false . func (d *DocumentHistory) Redo() (string, bool) : This function redoes the most recent undone change, making it active again. It returns the change that was redone and a boolean indicating success. If there are no changes available to redo, it returns an empty string and false . func (d *DocumentHistory) GetChanges() []string : This function returns a list of all applied changes in the order they were applied.

Methods Implementation with Stacks

To implement these functions efficiently, we'll use two slices to simulate stack behavior. Slices in Go allow dynamic resizing and efficient element insertion/removal from the end. This LIFO (Last In, First Out) property is ideal for keeping track of applied changes and undone changes. The most recent change is always at the end, making it easy to undo and redo. Let's break down each function's implementation and study how they interact with the slices.

Step 1: Defining the Struct

Let's implement the solution step by step. First, we define our struct and set up the initial state. Go package main type DocumentHistory struct {changesStack []string redoStack []string} Here, DocumentHistory is the struct, and we initialize two slices: changesStack to act as our stack of applied changes and redoStack for undone changes.

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// ... previous code

func (d *DocumentHistory) ApplyChange(change string) {
    d.changesStack = append(d.changesStack, change)
    d.redoStack = d.redoStack[:0] // clear the redo stack
}

// ... previous code

func (d *DocumentHistory) ApplyChange(change string) {
    d.changesStack = append(d.changesStack, change)
    d.redoStack = d.redoStack[:0] // clear the redo stack
}

// ... previous code

func (d *DocumentHistory) Undo() (string, bool) {
    if len(d.changesStack) == 0 {
        return "", false
    }
    change := d.changesStack[len(d.changesStack)-1]
    d.changesStack = d.changesStack[:len(d.changesStack)-1]
    d.redoStack = append(d.redoStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) Undo() (string, bool) {
    if len(d.changesStack) == 0 {
        return "", false
    }
    change := d.changesStack[len(d.changesStack)-1]
    d.changesStack = d.changesStack[:len(d.changesStack)-1]
    d.redoStack = append(d.redoStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) Redo() (string, bool) {
    if len(d.redoStack) == 0 {
        return "", false
    }
    change := d.redoStack[len(d.redoStack)-1]
    d.redoStack = d.redoStack[:len(d.redoStack)-1]
    d.changesStack = append(d.changesStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) Redo() (string, bool) {
    if len(d.redoStack) == 0 {
        return "", false
    }
    change := d.redoStack[len(d.redoStack)-1]
    d.redoStack = d.redoStack[:len(d.redoStack)-1]
    d.changesStack = append(d.changesStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) GetChanges() []string {
    return append([]string(nil), d.changesStack...)
}

// ... previous code

func (d *DocumentHistory) GetChanges() []string {
    return append([]string(nil), d.changesStack...)
}

// ... previous code

func (d *DocumentHistory) ApplyChange(change string) {
    d.changesStack = append(d.changesStack, change)
    d.redoStack = d.redoStack[:0] // clear the redo stack
}

// ... previous code

func (d *DocumentHistory) Undo() (string, bool) {
    if len(d.changesStack) == 0 {
        return "", false
    }
    change := d.changesStack[len(d.changesStack)-1]
    d.changesStack = d.changesStack[:len(d.changesStack)-1]
    d.redoStack = append(d.redoStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) Redo() (string, bool) {
    if len(d.redoStack) == 0 {
        return "", false
    }
    change := d.redoStack[len(d.redoStack)-1]
    d.redoStack = d.redoStack[:len(d.redoStack)-1]
    d.changesStack = append(d.changesStack, change)
    return change, true
}

// ... previous code

func (d *DocumentHistory) GetChanges() []string {
    return append([]string(nil), d.changesStack...)
}