package wing

// Sample is one backtest observation: the human-decided wing of an existing
// page, and what the two independent opinions said about it with the wing
// label removed.
type Sample struct {
	Truth      string
	Suggested  string // classifier's wing, "" if it abstained or failed
	Confidence float64
	ScorerTop  string // scorer's single best wing, "" if no clear opinion
}

// Result is the policy outcome at one threshold.
type Result struct {
	N         int
	Auto      int     // placed without a human
	Correct   int     // of Auto, matching Truth
	Coverage  float64 // Auto / N
	Precision float64 // Correct / Auto; 0 when Auto == 0
}

// Evaluate applies the Resolver's classified-path rule (confident, and the
// scorer agrees) to recorded samples. Eligibility is not modelled: callers
// backtest only on wings they would allow.
func Evaluate(samples []Sample, threshold float64) Result {
	r := Result{N: len(samples)}
	for _, s := range samples {
		if s.Suggested == "" || s.Confidence < threshold || s.ScorerTop != s.Suggested {
			continue
		}
		r.Auto++
		if s.Suggested == s.Truth {
			r.Correct++
		}
	}
	if r.N > 0 {
		r.Coverage = float64(r.Auto) / float64(r.N)
	}
	if r.Auto > 0 {
		r.Precision = float64(r.Correct) / float64(r.Auto)
	}
	return r
}