package domain

import (
	"sort"
	"strings"

	"git.cin.su/m/Assistant/contracts/interaction"
)

const (
	gen2ContextMaxCandidates = 4
	gen2ContextMaxBytes      = 2048
)

type ContextFragment struct {
	UtteranceID interaction.HumanUtteranceID
	Text        string
	ScopeRef    string
	Relevance   int
	Historical  bool
}

type ContextProjection struct {
	Text                       string
	Source                     string
	UsedPersonalMemoryFallback bool
	Fragments                  []ContextFragment
	Historical                 []ContextFragment
}

// BuildGen2Context is a read-side projection over canonical utterance history.
// PersonalMemory remains a compatibility fallback and is never written here.
func BuildGen2Context(history []interaction.HumanUtterance) ContextProjection {
	return BuildScopedGen2Context(history, "")
}

// BuildScopedGen2Context is the Gen2 retrieval boundary for household
// context. The caller supplies already-authorized history; this defensive
// filter prevents accidental cross-principal projection when a mixed source
// is passed during degraded operation.
func BuildScopedGen2Context(history []interaction.HumanUtterance, principalID string) ContextProjection {
	return BuildScopedGen2ContextForQuery(history, nil, principalID, "", "")
}

// BuildScopedGen2ContextForQuery projects bounded, explicit human assertions
// from the canonical Interaction history. Principal and typed project refs are
// hard filters before relevance ranking. Older values remain lineage in
// Historical and are never represented as the current value.
func BuildScopedGen2ContextForQuery(history []interaction.HumanUtterance, references []interaction.ProjectReference, principalID, focusProjectID, query string) ContextProjection {
	if principalID != "" {
		scoped := make([]interaction.HumanUtterance, 0, len(history))
		for _, item := range history {
			if item.PrincipalID == "" || string(item.PrincipalID) == principalID {
				scoped = append(scoped, item)
			}
		}
		history = scoped
	}
	projectRefs := make(map[interaction.HumanUtteranceID][]interaction.ProjectReference, len(references))
	for _, ref := range references {
		projectRefs[ref.UtteranceID] = append(projectRefs[ref.UtteranceID], ref)
	}
	assertions := explicitAssertionCandidates(history, projectRefs, focusProjectID, query)
	if len(assertions) > 0 {
		current, historical := selectCurrentAssertions(assertions)
		return contextProjectionFromAssertions(current, historical)
	}
	text := CompilePersonalMemory(history).ContextText()
	if text != "" {
		return ContextProjection{Text: text, Source: "retrieval:interaction-utterances"}
	}
	return ContextProjection{Text: text, Source: "personal-memory-v1-fallback", UsedPersonalMemoryFallback: true}
}

type assertionCandidate struct {
	fragment ContextFragment
	subject  string
	observed int64
	corrects interaction.HumanUtteranceID
}

func explicitAssertionCandidates(history []interaction.HumanUtterance, projectRefs map[interaction.HumanUtteranceID][]interaction.ProjectReference, focusProjectID, query string) []assertionCandidate {
	queryTokens := significantContextTokens(query)
	result := make([]assertionCandidate, 0)
	for _, utterance := range history {
		subject, value, ok := explicitAssertion(utterance.Content)
		if !ok {
			continue
		}
		refs := projectRefs[utterance.ID]
		scopeRef := ""
		if focusProjectID != "" {
			matched := false
			for _, ref := range refs {
				if string(ref.ProjectID) == focusProjectID {
					matched = true
					scopeRef = focusProjectID
					break
				}
			}
			if !matched {
				continue
			}
		} else if len(refs) == 1 {
			scopeRef = string(refs[0].ProjectID)
		}
		relevance := contextRelevance(subject, queryTokens)
		if len(queryTokens) > 0 && relevance == 0 {
			continue
		}
		result = append(result, assertionCandidate{
			fragment: ContextFragment{UtteranceID: utterance.ID, Text: subject + " = " + value, ScopeRef: scopeRef, Relevance: relevance},
			subject:  normalizedContextSubject(subject),
			observed: utterance.ReceivedAtUnixMillis,
			corrects: utterance.CorrectsUtteranceID,
		})
	}
	return result
}

func selectCurrentAssertions(candidates []assertionCandidate) ([]ContextFragment, []ContextFragment) {
	latest := make(map[string]assertionCandidate)
	for _, candidate := range candidates {
		current, exists := latest[candidate.subject]
		if !exists || supersedesAssertion(candidate, current) {
			latest[candidate.subject] = candidate
		}
	}
	current := make([]ContextFragment, 0, len(latest))
	historical := make([]ContextFragment, 0, len(candidates)-len(latest))
	for _, candidate := range candidates {
		selected := latest[candidate.subject]
		if candidate.fragment.UtteranceID == selected.fragment.UtteranceID {
			current = append(current, candidate.fragment)
			continue
		}
		candidate.fragment.Historical = true
		historical = append(historical, candidate.fragment)
	}
	sort.SliceStable(current, func(i, j int) bool {
		if current[i].Relevance != current[j].Relevance {
			return current[i].Relevance > current[j].Relevance
		}
		return current[i].UtteranceID > current[j].UtteranceID
	})
	return current, historical
}

// supersedesAssertion first respects an explicit correction relation, then
// uses observation time only as a deterministic tie-breaker. Applicability is
// already established by principal and typed Scope filtering before this step.
func supersedesAssertion(candidate, current assertionCandidate) bool {
	if candidate.corrects == current.fragment.UtteranceID {
		return true
	}
	if current.corrects == candidate.fragment.UtteranceID {
		return false
	}
	return candidate.observed > current.observed || candidate.observed == current.observed && candidate.fragment.UtteranceID > current.fragment.UtteranceID
}

func contextProjectionFromAssertions(current, historical []ContextFragment) ContextProjection {
	selected := make([]ContextFragment, 0, len(current))
	text := make([]string, 0, len(current))
	usedBytes := 0
	for _, candidate := range current {
		if len(selected) == gen2ContextMaxCandidates {
			break
		}
		bytes := len([]byte(candidate.Text))
		if bytes == 0 || usedBytes+bytes > gen2ContextMaxBytes {
			continue
		}
		usedBytes += bytes
		selected = append(selected, candidate)
		text = append(text, candidate.Text)
	}
	if len(selected) == 0 {
		return ContextProjection{Source: "retrieval:interaction-assertions", Historical: historical}
	}
	return ContextProjection{Text: strings.Join(text, "\n"), Source: "retrieval:interaction-assertions", Fragments: selected, Historical: historical}
}

func explicitAssertion(message string) (string, string, bool) {
	text := strings.TrimSpace(StripAssistantVocative(message))
	if text == "" || strings.Contains(text, "?") {
		return "", "", false
	}
	lower := strings.ToLower(text)
	if index := strings.Index(lower, "запомни:"); index >= 0 {
		text = strings.TrimSpace(text[index+len("запомни:"):])
		lower = strings.ToLower(text)
	}
	for _, prefix := range []string{"запомни:", "запомни", "помни:"} {
		if strings.HasPrefix(lower, prefix) {
			text = strings.TrimSpace(text[len(prefix):])
			break
		}
	}
	for _, separator := range []string{"=", "—"} {
		subject, value, found := strings.Cut(text, separator)
		if !found {
			continue
		}
		subject, value = strings.TrimSpace(subject), strings.TrimSpace(value)
		if subject != "" && value != "" && len([]rune(subject)) <= 160 && len([]rune(value)) <= 512 {
			return subject, value, true
		}
	}
	return "", "", false
}

func normalizedContextSubject(subject string) string {
	return strings.Join(significantContextTokens(subject), " ")
}

func significantContextTokens(value string) []string {
	ignored := map[string]struct{}{"какой": {}, "какая": {}, "какое": {}, "какие": {}, "текущий": {}, "текущая": {}, "текущее": {}, "я": {}, "ты": {}, "назвал": {}, "назвала": {}, "сообщил": {}, "сообщила": {}}
	result := make([]string, 0)
	seen := make(map[string]struct{})
	for _, token := range semanticTokens(value) {
		if len([]rune(token)) < 3 {
			continue
		}
		if _, skip := ignored[token]; skip {
			continue
		}
		if _, duplicate := seen[token]; duplicate {
			continue
		}
		seen[token] = struct{}{}
		result = append(result, token)
	}
	return result
}

func contextRelevance(subject string, queryTokens []string) int {
	if len(queryTokens) == 0 {
		return 1
	}
	subjectTokens := significantContextTokens(subject)
	matched := 0
	for _, query := range queryTokens {
		for _, token := range subjectTokens {
			if query == token {
				matched++
				break
			}
		}
	}
	return matched
}