Lesson 01 · The URI value and a bare path

The URI value and a bare path

Every URI, however complex, decomposes into the same five components. Today you define the result type that holds all five and give the library its public Parse entry point, starting with the simplest input of all - a bare path with nothing else around it.

The goal

Define the URI struct with all five components and parse an input that is just a path.

Start here - the target

TO DO

Scenario: Parsing a bare path

Giventhe input string "foo/bar"

WhenParse is called on it

Thenthe result has Path equal to "foo/bar"

AndScheme is empty, HasAuthority is false, HasQuery is false, and HasFragment is false

Background

RFC 3986 describes every URI with one generic syntax: scheme://authority/path?query#fragment. Not every URI has all five parts, but every URI is some subset of exactly these five components, always in this order. The parser’s whole job is to find the boundaries between them, so the natural shape for the result is a struct with a field per component.

A few of those components can be absent rather than merely empty, and that difference will matter later - a URI with no query is not the same as one with an empty query. So alongside the string fields you carry Has... booleans for the parts that can be present-but-empty. Define the entire struct now, even though most fields stay zero today; every later lesson fills in one more boundary. Start at the far end of the grammar: an input with no scheme, no //, no ?, and no # is nothing but a path, so Parse sets Path to the whole string and leaves the rest empty.

Make it work

// the whole library grows around this one result type
type URI struct {
  Scheme                   string
  Authority                string
  HasAuthority             bool
  Userinfo                 string
  HasUserinfo              bool
  Host, Port               string
  HasPort                  bool
  Path                     string
  Query                    string
  HasQuery                 bool
  Fragment                 string
  HasFragment              bool
}
func Parse(s string) *URI { return &URI{Path: s} }

CheckpointDONE

You have an importable Parse that returns a typed URI whose Path holds the whole input. Commit and stop here.