package iace

import "github.com/google/uuid"

// ScreenResult is the deterministic GT verdict for one proposed supersession.
type ScreenResult struct {
	RecallBefore float64 `json:"recall_before"`
	RecallAfter  float64 `json:"recall_after"`
	KeepGT       string  `json:"keep_gt,omitempty"` // GT entry the keeper credits (if any)
	DropGT       string  `json:"drop_gt,omitempty"` // GT entry the drop credits (if any)
	DistinctGT   bool    `json:"distinct_gt"`       // keep & drop credit DIFFERENT GT entries -> distinct hazards
	Safe         bool    `json:"safe"`              // recall preserved AND not distinct
}

// ScreenSupersession is the WALL between "propose" and "decide". A proposal is
// safe only if BOTH deterministic checks pass:
//
//  1. RECALL is not reduced when the drop-hazard (and its mitigations) is removed
//     — otherwise the drop is load-bearing for GT coverage.
//  2. The two hazards do NOT credit DIFFERENT ground-truth entries. Recall alone
//     is necessary but not sufficient: two genuinely distinct hazards that share
//     the same measures (e.g. hot boiler surface vs hot ware on unloading) keep
//     recall at 100% when one is dropped, yet must NOT be merged. If keep and
//     drop each match a different GT entry, they are distinct.
//
// Whatever survives both is still only RECALL-SAFE — a candidate for a human (and
// in slice 2, an LLM) to confirm semantically. Deterministic; reuses
// CompareBenchmark; touches neither the library nor the runtime.
func ScreenSupersession(gt *GroundTruth, hazards []Hazard, mits []Mitigation, keepHazardName, dropHazardName string) ScreenResult {
	before := CompareBenchmark(gt, hazards, mits)

	gtOf := map[string]string{}
	for _, p := range before.MatchedPairs {
		gtOf[p.EngineHazard.Name] = p.GTEntry.Nr
	}
	keepGT, dropGT := gtOf[keepHazardName], gtOf[dropHazardName]
	distinct := keepGT != "" && dropGT != "" && keepGT != dropGT

	kept := make([]Hazard, 0, len(hazards))
	dropped := map[uuid.UUID]bool{}
	for _, h := range hazards {
		if h.Name == dropHazardName {
			dropped[h.ID] = true
			continue
		}
		kept = append(kept, h)
	}
	keptMits := make([]Mitigation, 0, len(mits))
	for _, m := range mits {
		if !dropped[m.HazardID] {
			keptMits = append(keptMits, m)
		}
	}
	after := CompareBenchmark(gt, kept, keptMits)

	return ScreenResult{
		RecallBefore: before.CoverageScore, RecallAfter: after.CoverageScore,
		KeepGT: keepGT, DropGT: dropGT, DistinctGT: distinct,
		Safe: after.CoverageScore >= before.CoverageScore && !distinct,
	}
}