Gophercises - 4 - Link

Problem

• https://github.com/gophercises/link
• https://gophercises.com/exercises/link

Solutions

• link: link package.
• main: Use link package to extract links from HTML.

Lessons Learned

/x/net/html

• Read the package example: https://godoc.org/golang.org/x/net/html
• Token struct:

  type Token struct {
      Type     TokenType
      DataAtom atom.Atom
      Data     string
      Attr     []Attribute
  }
  

• Type can give us information about what kind of token it is. Important ones for this exercise are:
  • StartTagToken: <a href>
  • EndTagToken: </a>
  • TextToken: Text in between. Using text nodes will skip other elements inside the link.
• Data contains the data in the node.
  • Anchor tags: a.
  • Text nodes: The actual text of the node.
• Attribute is of type:

  type Attribute struct {
      Namespace, Key, Val string
  }
  

• Key is the name of the attribute and Value is the value.
  • <a href="example.net">: key = href and value = example.net.

Parse

Parse is easy.

• Go through the nodes. If you reach a start anchor tag, set the capturing flag to start capturing. Store the href.
• While capturing, add the text of every text node (trim all white space but add a space between nodes).
• After reaching the end anchor tag, stop capturing and store the link.
• Add link to the links slice.

Issues:

• Nested links are ignored. Child links are not stored and their text is stored as part of the parent link.
  • For an example run go run main.go -f ex5.html.

strings.Builder

• Example: https://golang.org/pkg/strings/#example_Builder

var sb strings.Builder  // Create the builder.
sb.WriteString("whatever")  // Write to it. We can use fmt.Sprintf as param too.
return sb.String()  // Get the final string.