package llamaswap

import (
	"context"
	"fmt"
	"io"
	"net/http"
)

// Health reports whether the llama-swap instance is reachable (GET
// {base}/health, which answers "OK" without touching any model). A nil error
// means the proxy itself is up — it says nothing about how long a subsequent
// request will take (a cold model swap can still block for minutes). Bound
// the probe with a short context deadline; the client has no timeout by
// design.
func (p *Provider) Health(ctx context.Context) error {
	if p.baseURL == "" {
		return fmt.Errorf("llama-swap provider %q: no base URL configured (set one via WithBaseURL or an LLM_* env DSN)", p.name)
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, p.baseURL+"/health", nil)
	if err != nil {
		return fmt.Errorf("llama-swap: build request: %w", err)
	}
	if p.token != "" {
		req.Header.Set("Authorization", "Bearer "+p.token)
	}
	resp, err := p.client.Do(req)
	if err != nil {
		return fmt.Errorf("llama-swap: health probe: %w", err)
	}
	defer resp.Body.Close()
	_, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, 1<<10))
	if resp.StatusCode/100 != 2 {
		return &apiHealthError{status: resp.StatusCode}
	}
	return nil
}

// apiHealthError distinguishes "reachable but unhealthy" from transport
// failure without pulling in the llm error taxonomy for a probe.
type apiHealthError struct{ status int }

func (e *apiHealthError) Error() string {
	return fmt.Sprintf("llama-swap: health endpoint returned status %d", e.status)
}