Resource loader: fetch and decode HTML pages #73

Phase 8 — Resource Loading + Character Encoding + Real Page Loading#

Implement the core resource loading infrastructure that fetches URLs and decodes their content.

Requirements#

• ResourceLoader struct that wraps the net crate's HttpClient
• Fetch a URL: given a URL string, resolve it, fetch via HTTP/HTTPS, and return the decoded body
• Content-Type handling: parse the response Content-Type to determine MIME type and charset
• Text decoding: use the encoding crate to decode response bytes to text (for HTML, CSS, etc.)
• Binary resources: return raw bytes for images and other binary content
• Error handling: network errors, DNS failures, TLS errors, HTTP errors (4xx, 5xx)
• Base URL tracking: track the document's base URL for resolving relative URLs

API#

pub struct ResourceLoader {
    client: HttpClient,
}

pub enum Resource {
    Html { text: String, base_url: Url, encoding: Encoding },
    Css { text: String, url: Url },
    Image { data: Vec<u8>, mime_type: String, url: Url },
    Other { data: Vec<u8>, mime_type: String, url: Url },
}

impl ResourceLoader {
    pub fn new() -> Self;
    pub fn fetch(&mut self, url: &Url) -> Result<Resource, LoadError>;
}

Acceptance Criteria#

• Can fetch HTML pages over HTTP and HTTPS
• Content-Type parsing extracts MIME type and charset
• Text resources are decoded using detected/specified encoding
• Binary resources (images) returned as raw bytes
• Relative URL resolution works with base URL
• Error types cover network, protocol, and HTTP status errors
• No external dependencies, no unsafe
• Integration tests (can be skipped in CI if no network)

Dependencies#

Depends on: Encoding sniffing (for charset detection), net crate (already complete)