Replace Value Text Over Multiple Lines-CodePudding

I have multiple text files and I need to replace a string inside with something else. The text files can have up to 500 of this reoccurrences .

The example below I need to replace everything after Synopsis with whatever string I choose such as not available.

I can read the file and I even tried to make 2 markers start and end but not working:

List of all books

Romance

Book number: 1
Title : Something Title
Author : Some Author
ISBN: 45425425423
Written Date : Some date
Release Date: Some date
Characters: Blah Blah
Genre: Romance
Synopsis : Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah


Book number: 2
Title : Something Title
Author : Some Author
ISBN: 45425425423
Written Date : Some date
Release Date: Some date
Characters: Blah Blah
Genre: Romance
Synopsis : Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah

Book number: 3
Title : Something Title
Author : Some Author
ISBN: 45425425423
Written Date : Some date
Release Date: Some date
Characters: Blah Blah
Genre: Romance
Synopsis : Blah Blah Blah Blah Blah Blah Blah Blah
       Blah Blah Blah Blah Blah Blah Blah Blah

Comedy

Book number: 1
Title : Something Title
Author : Some Author
ISBN: 45425425423
Written Date : Some date
Release Date: Some date
Characters: Blah Blah
Genre: Romance
Synopsis : Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah
        Blah Blah Blah Blah Blah Blah Blah Blah

This is the code i tried so far.

string[] filelines = File.ReadAllLines(@"file.txt", Enconding.UTF8)

string markS = "Synopsis :"

string MarkE = "Book number:"

for (int i = 0; i < fileLines.Length; i  )
{
    string line = fileLines[i];
   
    int start = line.IndexOf(markS);

    int end = line.LastIndexOf(markE);
    Console.WriteLine(start   " "   end);
    // if (start >= 0 && end >= 0)
    if (start >= 0 && end >= 0)
    {
        Console.WriteLine(line);
        int length = line.IndexOf(markE)   markE.Length - start;
        //include the markers in the substring
        //in case the substring occurs elsewhere without the markers
        var textToReplace = line.Substring(start, length);

        //add the markers to the relacement
        string replacement = markS   replacedText   markE;
        var result = line.Replace(textToReplace, replacement);
        fileLines[i] = result;

    }
    File.WriteAllLines(@"test2.txt", fileLines);`your text`
}

CodePudding user response：

Using regular expressions and Regex.Replace we can replace the text as so:

var pattern = @"(^Synopsis\s:)(. ?)(^Book\snumber|\Z)";

var replacements = 
      Regex.Replace(text, 
                    pattern, 
                    $"$1 Jabberwocky {Environment.NewLine}$3", 
                    RegexOptions.Multiline | RegexOptions.Singleline);

The above code will replace the multline "Synopsis" value with "Jabberwocky".

You may need to tweak the (^Book\snumber|\Z) capture with the section headers like (^Book\snumber|Romance|Comedy|\Z). But I leave that up to you to work out since it's your data.

CodePudding user response：

Your post states that you need to replace a string inside with something else and you could consider the entire file as "one long string" and do some processing on that. The Regex solution is probably a great way to go in that case.

But I read your code carefully from the perspective of what you're actually trying to do. Ok, so my crystal ball isn't 100% but I believe that if we meet back up a few weeks from now, it will have occurred to you want certain elements:

A class that represents a Book.
A serialization method (like Json) that can take a file and turn it into a Book and vice versa.
A way to search the books (like SQLite) based on the properties in the Book class.

Having a Book class would simplify the substitution that you want to do because the Synopsis property would already be separated out. Then you could perform a standard string.Replace in a targeted way.

Book class

class Book
{
    public string? BookNumber { get; set; }
    public string? Title { get; set; }
    public string? Author { get; set; }
    public string? ISBN { get; set; }
    public string? Written { get; set; }
    public string? Release { get; set; }
    public string? Characters { get; set; }
    public string? Genre { get; set; }
    public string? Synopsis { get; set; }
    // Display
    public override string ToString()
    {
        return
            $"Book number : {BookNumber}{Environment.NewLine}"  
            $"Title : {Title}{Environment.NewLine}"  
            $"Author : {Author}{Environment.NewLine}"  
            $"ISBN : {ISBN}{Environment.NewLine}"  
            $"Written Date : {Written}{Environment.NewLine}"  
            $"Release Date : {Release}{Environment.NewLine}"  
            $"Characters : {Characters}{Environment.NewLine}"  
            $"Genre : {Genre}{Environment.NewLine}"  
            $"Synopsis : {Synopsis}{Environment.NewLine}";
    }
}

Replace:

book.Synopsis = book.Synopsis.Replace("Blah", "Marklar");

Serialization - The hard way

You stated that the .txt files are on disk. Here's a method that uses the string representations in your post to turn a "file" into a Book.

public Book(string file)
{
    var synopsis = new StringBuilder();
    foreach (var line in File.ReadAllLines(file))
    {
        var parse = line.Split(':').Select(_ => _.Trim()).ToArray();
        if (parse.Length == 1)
        {
            synopsis.Append("\t"   parse[0]   Environment.NewLine);
        }
        else
        {
            var property = parse[0];
            switch (property)
            {
                case "Book number": BookNumber = parse[1]; break;
                case "Title": Title = parse[1]; break;
                case "Author": Author = parse[1]; break;
                case "ISBN": ISBN = parse[1]; break;
                case "Written Date": Written = parse[1]; break;
                case "Release Date": Release = parse[1]; break;
                case "Characters": Characters = parse[1]; break;
                case "Genre": Genre = parse[1]; break;
                case "Synopsis": synopsis.Append(parse[1]   Environment.NewLine); break;
                default: Debug.Assert(false, $"Error reading '{property}'"); break;
            }
        }
    }
    Synopsis = synopsis.ToString();
}

That's a lot of work, but now you can replace value over multiple lines starting with a raw file:

book = new Book("492C9F2A7E73.txt");
book.Synopsis = book.Synopsis.Replace("Blah", "Marklar");

Serialization - An easier way

But also please consider using something like the Newtonsoft.Json NuGet to simplify your serialization. It still writes the file in plain text and you'll even see the ':' character used in a similar way to your file listings. But the format lets Json reconstruct a Book object directly.

SAVE

var path = Path.Combine(dir, $"{book.ISBN}.json");
File.WriteAllText(path, JsonConvert.SerializeObject(book));

Result in file (this is after doing the replacement):

{
  "BookNumber": "2",
  "Title": "Something Title",
  "Author": "Some Author",
  "ISBN": "7E092CB94CCD",
  "Written": "Some date",
  "Release": "Some date",
  "Characters": "Blah Blah",
  "Genre": "Romance",
  "Synopsis": "Marklar Marklar Marklar Marklar Marklar Marklar Marklar Marklar\r\n\tMarklar Marklar Marklar Marklar Marklar Marklar Marklar Marklar\r\n\tMarklar Marklar Marklar Marklar Marklar Marklar Marklar Marklar\r\n\tMarklar Marklar Marklar Marklar Marklar Marklar Marklar Marklar\r\n"
}

LOAD

var book = JsonConvert.DeserializeObject<Book>(File.ReadAllText("492C9F2A7E73.json"));

QUERY

var romanceBooks = database.Query<Book>("SELECT * FROM books WHERE Genre='Romance'");

There's more than one way to do what you asked. The benefit of doing something like this is to set you up going forward for a search engine using the Book class.