package mcpclient

import (
	"flag"
	"net/http"
)

func httpClientWithHeaders(headers map[string]string) *http.Client {
	base := http.DefaultTransport
	if isolated := mcpHTTPClient(); isolated != nil {
		base = isolated.Transport
	}
	if len(headers) == 0 {
		return &http.Client{Transport: base}
	}
	return &http.Client{Transport: &headerRoundTripper{
		base:    base,
		headers: headers,
	}}
}

type headerRoundTripper struct {
	base    http.RoundTripper
	headers map[string]string
}

func (h *headerRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	clone := req.Clone(req.Context())
	for k, v := range h.headers {
		clone.Header.Set(k, v)
	}
	return h.base.RoundTrip(clone)
}

// mcpHTTPClient returns an isolated *http.Client when running
// inside tests, or nil for production. During tests,
// httptest.Server.Close() calls
// http.DefaultTransport.CloseIdleConnections(), which disrupts
// any MCP client sharing that transport. When DefaultTransport
// is a *http.Transport it is cloned; otherwise a minimal
// transport with ProxyFromEnvironment is created as a fallback.
func mcpHTTPClient() *http.Client {
	if flag.Lookup("test.v") == nil {
		return nil
	}
	if dt, ok := http.DefaultTransport.(*http.Transport); ok {
		return &http.Client{Transport: dt.Clone()}
	}
	return &http.Client{Transport: &http.Transport{
		Proxy: http.ProxyFromEnvironment,
	}}
}