package validators

import (
	"context"
	"fmt"
	"strings"

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

type ProposalShapeValidator struct{}

func (v ProposalShapeValidator) Name() string { return "proposal_shape" }

func (v ProposalShapeValidator) Validate(_ context.Context, req Request) (Result, error) {
	decisions := make([]Decision, 0, len(req.CandidateProposal))
	for _, c := range req.CandidateProposal {
		switch {
		case c.TargetSegmentID <= 0:
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonInvalidTargetSegment, "proposal target segment id must be positive"))
		case c.OriginalText == "":
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonEmptyOriginalText, "proposal original_text must not be empty"))
		case c.Confidence < 0.0 || c.Confidence > 1.0:
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonInvalidConfidence, "proposal confidence must be between 0.0 and 1.0"))
		default:
			decisions = append(decisions, approval(c.ProposalIndex))
		}
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: v.Name(), Decisions: decisions}, nil
}

type ConfidenceThresholdValidator struct{}

func (v ConfidenceThresholdValidator) Name() string { return "confidence_threshold" }

func (v ConfidenceThresholdValidator) Validate(_ context.Context, req Request) (Result, error) {
	threshold := req.Settings.ConfidenceThreshold
	decisions := make([]Decision, 0, len(req.CandidateProposal))
	for _, c := range req.CandidateProposal {
		if c.Confidence < threshold {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonLowConfidence, fmt.Sprintf("confidence %.4f below threshold %.4f", c.Confidence, threshold)))
			continue
		}
		decisions = append(decisions, approval(c.ProposalIndex))
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: v.Name(), Decisions: decisions}, nil
}

type OriginalTextPresenceValidator struct{}

func (v OriginalTextPresenceValidator) Name() string { return "original_text_presence" }

func (v OriginalTextPresenceValidator) Validate(_ context.Context, req Request) (Result, error) {
	section := req.sectionLookup()

	decisions := make([]Decision, 0, len(req.CandidateProposal))
	for _, c := range req.CandidateProposal {
		position, ok := section.Position(c.TargetSegmentID)
		if !ok {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonMissingTargetSegment, "target segment was not found"))
			continue
		}
		if !strings.Contains(section.segments[position].Text, c.OriginalText) {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonMissingOriginalText, "original_text was not found in current segment text"))
			continue
		}
		decisions = append(decisions, approval(c.ProposalIndex))
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: v.Name(), Decisions: decisions}, nil
}

type NonEmptyResultingSegmentValidator struct{}

func (v NonEmptyResultingSegmentValidator) Name() string { return "non_empty_resulting_segment" }

func (v NonEmptyResultingSegmentValidator) Validate(_ context.Context, req Request) (Result, error) {
	req.Section = req.sectionLookup()

	decisions := make([]Decision, 0, len(req.CandidateProposal))
	for _, c := range req.CandidateProposal {
		preview := req.Preview(c)
		if preview.SkipReason == proposals.SkipReasonEmptyResultingText {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonEmptyResultingText, "proposal would leave the segment empty"))
			continue
		}
		decisions = append(decisions, approval(c.ProposalIndex))
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: v.Name(), Decisions: decisions}, nil
}

type NoEffectValidator struct{}

func (v NoEffectValidator) Name() string { return "no_effect" }

func (v NoEffectValidator) Validate(_ context.Context, req Request) (Result, error) {
	decisions := make([]Decision, 0, len(req.CandidateProposal))
	for _, c := range req.CandidateProposal {
		if c.OriginalText == c.CorrectedText {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonNoEffect, "original_text and corrected_text are identical"))
			continue
		}
		decisions = append(decisions, approval(c.ProposalIndex))
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: v.Name(), Decisions: decisions}, nil
}

func ValidateProtectedTerms(req Request) (Result, error) {
	var vocab ProtectedVocabulary
	if req.GlossaryView != nil {
		vocab = req.GlossaryView.Protection
	} else {
		vocab = NewProtectedVocabulary(req.ProtectedTerms)
	}
	decisions := make([]Decision, 0, len(req.CandidateProposal))
	glossaryStage := req.ModuleKey == modulecatalog.KeyGlossary
	for _, c := range req.CandidateProposal {
		reason := vocab.violationReason(c.OriginalText, c.CorrectedText)
		repetitionCleanup := reason != "" && req.ModuleKey == modulecatalog.KeySpokenWord
		if vocab.pattern != nil && (glossaryStage || repetitionCleanup) {
			req.Section = req.sectionLookup()
			if position, ok := req.Section.Position(c.TargetSegmentID); ok {
				segment := &req.Section.segments[position]
				preview := req.Preview(c)
				if preview.Applicable || (req.IndependentEvidence && preview.SkipReason == proposals.SkipReasonEmptyResultingText) {
					if glossaryStage {
						// A correction span may sit inside a longer exempt name.
						reason = vocab.violationReason(segment.Text, preview.CorrectedSegmentText)
					} else if vocab.preservesRepeatedIdentities(segment.Text, preview.CorrectedSegmentText) {
						reason = ""
					}
				}
			}
		}
		if reason != "" {
			decisions = append(decisions, rejection(c.ProposalIndex, ReasonProtectedGlossaryTerm, reason))
			continue
		}
		decisions = append(decisions, approval(c.ProposalIndex))
	}
	if err := EnforceDecisionCardinality(req.CandidateProposal, decisions); err != nil {
		return Result{}, err
	}
	return Result{ValidatorName: "protected_terms", Decisions: decisions}, nil
}