package validators

import (
	"math"

	"gitea.maximumdirect.net/eric/audita/v3/internal/core/schema"
	"gitea.maximumdirect.net/eric/audita/v3/internal/framework/proposals"
)

// SectionLookup indexes the immutable source section shared by validation
// and revalidation. Application checks its own, changing transcript.
type SectionLookup struct {
	segments  []schema.Segment
	positions map[int]int
}

func NewSectionLookup(transcript *schema.Transcript) *SectionLookup {
	section := &SectionLookup{}
	if transcript != nil {
		section.segments = transcript.Segments
		section.positions = make(map[int]int, len(section.segments))
		for i, segment := range section.segments {
			section.positions[segment.ID] = i
		}
	}
	return section
}

func (s *SectionLookup) Position(id int) (int, bool) {
	position, ok := s.positions[id]
	return position, ok
}

func (r Request) sectionLookup() *SectionLookup {
	if r.Section != nil {
		return r.Section
	}
	return NewSectionLookup(r.WorkingTranscript)
}

// Preview reuses the replacement preview for this proposal index within one
// validation pass. A revision starts a new pass with its own preview map.
func (r Request) Preview(candidate proposals.EnrichedCorrectionProposal) proposals.SegmentPreviewResult {
	if preview, ok := r.Previews[candidate.ProposalIndex]; ok {
		return preview
	}
	section := r.sectionLookup()
	var segment *schema.Segment
	if position, ok := section.Position(candidate.TargetSegmentID); ok {
		segment = &section.segments[position]
	}
	correction := candidate.CorrectionProposal
	if r.IndependentEvidence && (math.IsNaN(correction.Confidence) || correction.Confidence < 0 || correction.Confidence > 1) {
		correction.Confidence = 0.5
	}
	preview := proposals.PreviewProposalForSegment(segment, correction, r.ReplacementPolicy)
	if r.Previews != nil {
		r.Previews[candidate.ProposalIndex] = preview
	}
	return preview
}