package npcs

import (
	"fmt"
	"sort"
	"strconv"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/npcs/identity"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared/diagnostics"
)

type proposalAssessment struct {
	safeGroups      []safeProposalGroup
	discardedGroups int
	issues          []string
}

type safeProposalGroup struct {
	members   []int
	canonical int
}

type assessedProposalGroup struct {
	members      []int
	canonical    int
	locallyValid bool
	conflicting  bool
}

func assessProposal(response normalizeProposalResponse, records []normalizedRecord, candidatePositions []int) proposalAssessment {
	positionsByKey := make(map[string][]int, len(candidatePositions))
	for _, position := range candidatePositions {
		if position < 0 || position >= len(records) {
			continue
		}
		key := identity.ComparisonKey(records[position].npc.Name)
		if key != "" {
			positionsByKey[key] = append(positionsByKey[key], position)
		}
	}
	groups := make([]assessedProposalGroup, len(response.DuplicateGroups))
	issues := make([]string, 0)
	owners := make(map[int][]int)

	for groupIndex, proposal := range response.DuplicateGroups {
		group, groupIssues := assessProposalGroup(proposal, positionsByKey)
		groups[groupIndex] = group
		for _, position := range group.members {
			owners[position] = append(owners[position], groupIndex)
		}
		for _, issue := range groupIssues {
			issues = append(issues, proposalIssue(groupIndex, issue))
		}
	}
	for groupIndex := range groups {
		for _, position := range groups[groupIndex].members {
			if len(owners[position]) > 1 {
				groups[groupIndex].conflicting = true
				break
			}
		}
		if groups[groupIndex].conflicting {
			issues = append(issues, proposalIssue(groupIndex, "overlapping_member"))
		}
	}

	assessment := proposalAssessment{issues: issues}
	for _, group := range groups {
		if !group.locallyValid || group.conflicting {
			assessment.discardedGroups++
			continue
		}
		assessment.safeGroups = append(assessment.safeGroups, safeProposalGroup{members: group.members, canonical: group.canonical})
	}
	return assessment
}

func assessProposalGroup(proposal normalizeProposalGroup, positionsByKey map[string][]int) (assessedProposalGroup, []string) {
	issues := make([]string, 0)
	members := make([]int, 0, len(proposal.Members))
	seenMembers := make(map[int]struct{}, len(proposal.Members))
	for _, name := range proposal.Members {
		position, issue := resolveCandidate(name, positionsByKey)
		if issue != "" {
			issues = append(issues, "member_"+issue)
			continue
		}
		if _, exists := seenMembers[position]; exists {
			issues = append(issues, "repeated_member")
			continue
		}
		seenMembers[position] = struct{}{}
		members = append(members, position)
	}
	canonical, canonicalIssue := resolveCandidate(proposal.CanonicalName, positionsByKey)
	if canonicalIssue != "" {
		issues = append(issues, "canonical_"+canonicalIssue)
	}
	if len(members) < 2 {
		issues = append(issues, "fewer_than_two_members")
	}
	if canonicalIssue == "" && !containsPosition(members, canonical) {
		issues = append(issues, "canonical_not_member")
	}
	sort.Ints(members)
	return assessedProposalGroup{
		members: members, canonical: canonical, locallyValid: len(issues) == 0,
	}, issues
}

func resolveCandidate(name string, positionsByKey map[string][]int) (position int, issue string) {
	key := identity.ComparisonKey(name)
	if key == "" {
		return 0, "blank"
	}
	positions := positionsByKey[key]
	if len(positions) == 0 {
		return 0, "unknown"
	}
	if len(positions) != 1 {
		return 0, "ambiguous"
	}
	return positions[0], ""
}

func containsPosition(positions []int, want int) bool {
	for _, position := range positions {
		if position == want {
			return true
		}
	}
	return false
}

func proposalIssue(groupIndex int, category string) string {
	return "group " + strconv.Itoa(groupIndex) + ": " + category
}

func applySafeGroups(records []normalizedRecord, groups []safeProposalGroup, order shared.SourceRefOrder) ([]normalizedRecord, []contracts.Warning) {
	byMember := make(map[int]safeProposalGroup, len(groups)*2)
	for _, group := range groups {
		for _, member := range group.members {
			byMember[member] = group
		}
	}
	output := make([]normalizedRecord, 0, len(records)-len(groups))
	warnings := make([]contracts.Warning, 0, len(groups))
	for index, record := range records {
		group, grouped := byMember[index]
		if !grouped {
			output = append(output, cloneRecord(record))
			continue
		}
		if group.members[0] != index {
			continue
		}
		consolidated := consolidateSemanticGroup(records, group, order)
		output = append(output, consolidated)
		warnings = append(warnings, semanticDuplicateWarning(consolidated, records[group.canonical]))
	}
	return output, warnings
}

func consolidateSemanticGroup(records []normalizedRecord, group safeProposalGroup, order shared.SourceRefOrder) normalizedRecord {
	output := cloneRecord(records[group.members[0]])
	output.npc.Name = records[group.canonical].npc.Name
	for _, member := range group.members[1:] {
		output.npc.SourceRefs = append(output.npc.SourceRefs, records[member].npc.SourceRefs...)
		output.inputIndexes = append(output.inputIndexes, records[member].inputIndexes...)
		if records[member].earliest < output.earliest {
			output.earliest = records[member].earliest
		}
	}
	output.inputIndexes = sortedUniqueIndexes(output.inputIndexes)
	output.npc.SourceRefs = order.Canonicalize(output.npc.SourceRefs)
	output.npc.ID = identity.DeriveID(output.npc.Name)
	return output
}

func semanticDuplicateWarning(record normalizedRecord, canonical normalizedRecord) contracts.Warning {
	details := make([]string, 0, len(record.inputIndexes)+1)
	for _, inputIndex := range record.inputIndexes {
		details = append(details, fmt.Sprintf("input index %d", inputIndex))
	}
	if canonical.earliest != record.earliest {
		details = append(details, fmt.Sprintf("canonical display name from input index %d", canonical.earliest))
	}
	return contracts.Warning{
		Scope:      npcScope(record.earliest),
		ReasonCode: ReasonCodeDuplicateNPCCollapsed,
		Message:    diagnostics.Aggregate("semantic duplicate consolidation", details),
	}
}