use std::path::{Component, Path, PathBuf};

use axum::http::{StatusCode, header};
use axum::response::{IntoResponse, Response};

use crate::smart::error::{SmartError, SmartResult};

pub async fn serve(bare: &Path, request_path: &str) -> SmartResult<Response> {
    let file = resolve_within_root(bare, request_path)?;
    match tokio::fs::read(&file).await {
        Ok(bytes) => {
            tracing::debug!(path = %request_path, bytes = bytes.len(), "serving dumb http object");
            Ok((
                StatusCode::OK,
                [(header::CONTENT_TYPE, guess_content_type(request_path))],
                bytes,
            )
                .into_response())
        }
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Err(SmartError::NotFound(format!(
            "file not found: {request_path}"
        ))),
        Err(e) => Err(SmartError::Io(e)),
    }
}

fn resolve_within_root(root: &Path, request_path: &str) -> SmartResult<PathBuf> {
    let mut base = root.to_path_buf();
    for component in Path::new(request_path).components() {
        match component {
            Component::Normal(part) => base.push(part),
            Component::CurDir => {}
            Component::ParentDir | Component::RootDir | Component::Prefix(_) => {
                tracing::warn!(path = %request_path, "dumb http path traversal denied");
                return Err(SmartError::Forbidden("path traversal denied".into()));
            }
        }
    }
    let canonical = base
        .canonicalize()
        .map_err(|_| SmartError::NotFound("file not found".into()))?;
    let root_canonical = root
        .canonicalize()
        .map_err(|_| SmartError::NotFound("repository not found".into()))?;
    if canonical.starts_with(&root_canonical) {
        Ok(canonical)
    } else {
        tracing::warn!(path = %request_path, "dumb http path escapes repository root");
        Err(SmartError::Forbidden("path escapes repository root".into()))
    }
}

fn guess_content_type(path: &str) -> &'static str {
    if path.ends_with("/info/refs") || path.ends_with("info/refs") {
        "text/plain; charset=utf-8"
    } else {
        "application/octet-stream"
    }
}