Route methods and canonical paths deliberately

A router answers two questions: does this path name a route, and does that route support this method? Keep those questions separate. GET /missing is 404. PUT /notes is 405 with an Allow header because /notes is a real collection route.

This API’s small route table is written out. Health supports GET/HEAD, the collection supports GET/POST, and an item supports GET/DELETE. A numeric path does not prove a stored note exists; the repository decides that later.

The parser is supplied in this exercise; complete the method dispatch. Use equality, not substring containment. HTTP method names are case-sensitive.

For item IDs, conversion and validation are different. Atoi can parse 01 or +1, but this route admits only the canonical positive decimal spelling from 1 through 1,000,000. A round trip through Itoa rejects aliases.

package main
import ("fmt";"strconv")
func main(){
for _,raw:=range []string{"1","01","+1","0"}{n,err:=strconv.Atoi(raw);ok:=err==nil&&n>0&&n<=1000000&&strconv.Itoa(n)==raw;fmt.Println(raw,ok)}
}

The handler passes URL.EscapedPath to the router. That preserves a spelling such as /notes/%31 instead of silently turning it into /notes/1. This is a deliberate teaching API policy; other APIs can choose a different normalization contract, but all layers must agree.

No slash cleaning, redirects or fallback page is part of this service. Paths with trailing or extra segments fail. A query string does not change the URL path. Method failures preserve an exact, stable Allow list for clients and tests.

Routing returns a decision rather than writing the response or mutating storage. This makes the table straightforward to test and keeps responsibilities visible in the final handler.

package main
import ("fmt";"net/url")
func main(){
u,_:=url.Parse("http://example.test/notes/12?view=short");fmt.Println(u.EscapedPath(),u.RawQuery)
}

Complete the dispatch and test every allowed method, several wrong methods, leading zeros, encoded digits and oversized IDs. Do not query the repository from the router.

Next we define a bounded request-body schema before any note can be created.