BASE_URL.md

Base URL and Endpoint Resolution

tinywasm/fetch allows you to simplify your requests by using a base URL and providing only the endpoint.

Priority Resolution

When building the final URL, the following priority is used:

1. Absolute URL: If the endpoint passed to Get, Post, etc., starts with http:// or https://, it is used directly.
2. Request BaseURL: If .BaseURL("...") is called on the request builder.
3. Global BaseURL: If fetch.SetBaseURL("...") was called previously.
4. WASM Origin: In WebAssembly environments (browsers), it defaults to location.origin.
5. Error: If none of the above are available, the request will fail with an error.

Global Base URL

You can set a global base URL once at the start of your application:

import "github.com/tinywasm/fetch"

func check() {
    fetch.SetBaseURL("https://api.example.com")

    // Request to https://api.example.com/users
    fetch.Get("/users").Send(...)
}

Per-Request Base URL

You can override the global base URL for a specific request:

fetch.Get("/data").
    BaseURL("https://other-api.com").
    Send(...)

Automatic WASM Origin

In a browser, if you don't set a base URL, it automatically uses the current origin:

// In browser at https://myapp.com
// Request to https://myapp.com/api/v1/status
fetch.Get("/api/v1/status").Send(...)

Endpoint Provider Interface

You can pass structures that implement the EndpointProvider interface directly:

type User struct {
    ID string
}

func (u User) HandlerName() string {
    return "/users"
}

func main() {
    user := User{ID: "123"}
    
    // Automatically uses "/users" as the endpoint
    fetch.Get(user).Send(...)
}

This is useful for creating type-safe API clients where the structure itself knows its endpoint.