package engine

import (
	"sort"

	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
)

type collectionPolicyScope struct {
	collections map[string]collectionPolicyEntry
}

type collectionPolicyEntry struct {
	destination Path
	policy      collectionPolicy
}

type collectionRecordPolicy struct {
	owner *collectionRecordOwner
	scope collectionPolicyScope
}

// The nonzero field ensures simultaneously live record owners have distinct
// addresses. The token is per-record ownership, not a source or identity key.
type collectionRecordOwner struct {
	marker byte
}

type projectedCollectionPolicy struct {
	path   Path
	policy collectionPolicy
}

func newCollectionRecordPolicy() collectionRecordPolicy {
	return collectionRecordPolicy{owner: &collectionRecordOwner{marker: 1}}
}

func retainedCollectionRecordPolicy(record collectionRecordPolicy) collectionRecordPolicy {
	return collectionRecordPolicy{
		owner: record.owner,
		scope: cloneCollectionPolicyScope(record.scope),
	}
}

func replacedCollectionRecordPolicy() collectionRecordPolicy {
	return newCollectionRecordPolicy()
}

func (policy *collectionPolicy) setRecordPolicy(record collectionRecordPolicy) {
	if record.owner == nil {
		record.owner = newCollectionRecordPolicy().owner
	}
	if policy.recordPolicies == nil {
		policy.recordPolicies = make(map[*collectionRecordOwner]collectionPolicyScope)
	}
	if _, exists := policy.recordPolicies[record.owner]; !exists {
		policy.recordOrder = append(policy.recordOrder, record.owner)
	}
	policy.recordPolicies[record.owner] = cloneCollectionPolicyScope(record.scope)
}

func (policy *collectionPolicy) setRecordPolicyAt(index int, record collectionRecordPolicy) {
	if index < 0 {
		return
	}
	if record.owner == nil {
		record.owner = newCollectionRecordPolicy().owner
	}
	if policy.recordPolicies == nil {
		policy.recordPolicies = make(map[*collectionRecordOwner]collectionPolicyScope)
	}
	for len(policy.recordOrder) <= index {
		owner := newCollectionRecordPolicy().owner
		policy.recordOrder = append(policy.recordOrder, owner)
		policy.recordPolicies[owner] = collectionPolicyScope{}
	}
	delete(policy.recordPolicies, policy.recordOrder[index])
	policy.recordOrder[index] = record.owner
	policy.recordPolicies[record.owner] = cloneCollectionPolicyScope(record.scope)
}

func (policy collectionPolicy) recordPolicyAt(index int) (collectionRecordPolicy, bool) {
	if index < 0 || index >= len(policy.recordOrder) {
		return collectionRecordPolicy{}, false
	}
	owner := policy.recordOrder[index]
	scope, ok := policy.recordPolicies[owner]
	if !ok {
		return collectionRecordPolicy{}, false
	}
	return collectionRecordPolicy{owner: owner, scope: cloneCollectionPolicyScope(scope)}, true
}

func collectionPolicyForReplacement(lower *collectionPolicy, current collectionPolicy) collectionPolicy {
	result := cloneCollectionPolicy(current)
	if !current.explicitModePresent && lower != nil && lower.explicitModePresent {
		result.explicitMode = lower.explicitMode
		result.explicitModePresent = true
		result.modeLocation = cloneLocation(lower.modeLocation)
	}
	return result
}

// collectionPolicyWithoutValue keeps identity and record ownership because no
// collection value was replaced. A key-only declaration can remain pending
// when no sequence is present, or validate the retained sequence immediately.
func collectionPolicyWithoutValue(
	lower *collectionPolicy,
	current collectionPolicy,
	retainedValue *document.Node,
	path Path,
) (collectionPolicy, []Diagnostic) {
	result := collectionPolicy{}
	if lower != nil {
		result = cloneCollectionPolicy(*lower)
	}
	if lower != nil && lower.identityPresent && current.identityPresent && !equalSequenceIdentityFields(lower.identityFields, current.identityFields) {
		return collectionPolicy{}, []Diagnostic{collectionPolicyConflictDiagnostic(
			path, current.identityLocation, lower.identityLocation,
			"collection identity declaration conflicts with retained identity",
		)}
	}
	if current.identityPresent {
		result.identityFields = cloneStrings(current.identityFields)
		result.identityPresent = true
		result.identityLocation = cloneLocation(current.identityLocation)
	}
	if current.explicitModePresent {
		result.explicitMode = current.explicitMode
		result.explicitModePresent = true
		result.modeLocation = cloneLocation(current.modeLocation)
	}
	if current.identityPresent && retainedValue != nil && retainedValue.Kind == document.Sequence {
		_, diagnostics := validateSequenceIdentity(retainedValue, path, result.identityFields, sequenceIdentityDiagnosticCodes{
			invalid: CodeSequenceInvalid, conflict: CodeSequenceConflict,
		})
		if len(diagnostics) != 0 {
			return collectionPolicy{}, diagnostics
		}
	}
	return result, nil
}

func (scope *collectionPolicyScope) set(destination Path, policy collectionPolicy) {
	if scope.collections == nil {
		scope.collections = make(map[string]collectionPolicyEntry)
	}
	scope.collections[destination.String()] = collectionPolicyEntry{
		destination: destination.clone(), policy: cloneCollectionPolicy(policy),
	}
}

func (scope collectionPolicyScope) at(destination Path) (collectionPolicy, bool) {
	entry, ok := scope.collections[destination.String()]
	if !ok {
		return collectionPolicy{}, false
	}
	return cloneCollectionPolicy(entry.policy), true
}

// retireCollectionPoliciesAtOrBelow clears YAML identity and record-owned state
// below a replaced ancestor while retaining independently scoped explicit modes.
func (scope *collectionPolicyScope) retireCollectionPoliciesAtOrBelow(ancestor Path) {
	if scope == nil {
		return
	}
	for key, entry := range scope.collections {
		if !pathHasPrefix(entry.destination, ancestor) {
			continue
		}
		clearCollectionIdentity(&entry.policy)
		scope.collections[key] = entry
	}
}

func projectCollectionPolicyScope(scope collectionPolicyScope, prefix Path) []projectedCollectionPolicy {
	keys := make([]string, 0, len(scope.collections))
	for key := range scope.collections {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	var projected []projectedCollectionPolicy
	for _, key := range keys {
		entry := scope.collections[key]
		concrete := appendDestination(prefix, entry.destination)
		projected = append(projected, projectedCollectionPolicy{path: concrete, policy: cloneCollectionPolicy(entry.policy)})
		for index, owner := range entry.policy.recordOrder {
			if recordScope, ok := entry.policy.recordPolicies[owner]; ok {
				projected = append(projected, projectCollectionPolicyScope(recordScope, concrete.Index(index))...)
			}
		}
	}
	return projected
}

func cloneCollectionPolicyScope(scope collectionPolicyScope) collectionPolicyScope {
	if scope.collections == nil {
		return collectionPolicyScope{}
	}
	cloned := collectionPolicyScope{collections: make(map[string]collectionPolicyEntry, len(scope.collections))}
	for key, entry := range scope.collections {
		cloned.collections[key] = collectionPolicyEntry{
			destination: entry.destination.clone(), policy: cloneCollectionPolicy(entry.policy),
		}
	}
	return cloned
}

func cloneCollectionPolicyScopeForInheritance(scope collectionPolicyScope) collectionPolicyScope {
	if scope.collections == nil {
		return collectionPolicyScope{}
	}
	cloned := collectionPolicyScope{collections: make(map[string]collectionPolicyEntry, len(scope.collections))}
	for key, entry := range scope.collections {
		cloned.collections[key] = collectionPolicyEntry{
			destination: entry.destination.clone(), policy: cloneCollectionPolicyForInheritance(entry.policy),
		}
	}
	return cloned
}

func cloneCollectionPolicy(policy collectionPolicy) collectionPolicy {
	cloned := policy
	cloned.identityFields = cloneStrings(policy.identityFields)
	cloned.identityLocation = cloneLocation(policy.identityLocation)
	cloned.modeLocation = cloneLocation(policy.modeLocation)
	if policy.recordOrder != nil {
		cloned.recordOrder = append([]*collectionRecordOwner(nil), policy.recordOrder...)
	}
	if policy.recordPolicies != nil {
		cloned.recordPolicies = make(map[*collectionRecordOwner]collectionPolicyScope, len(policy.recordPolicies))
		for owner, scope := range policy.recordPolicies {
			cloned.recordPolicies[owner] = cloneCollectionPolicyScope(scope)
		}
	}
	return cloned
}

func cloneCollectionPolicyForInheritance(policy collectionPolicy) collectionPolicy {
	cloned := policy
	cloned.identityFields = cloneStrings(policy.identityFields)
	cloned.identityLocation = cloneLocation(policy.identityLocation)
	cloned.modeLocation = cloneLocation(policy.modeLocation)
	if policy.recordOrder != nil {
		cloned.recordOrder = make([]*collectionRecordOwner, 0, len(policy.recordOrder))
	}
	if policy.recordPolicies != nil {
		cloned.recordPolicies = make(map[*collectionRecordOwner]collectionPolicyScope, len(policy.recordPolicies))
		for _, sourceOwner := range policy.recordOrder {
			owner := newCollectionRecordPolicy().owner
			cloned.recordOrder = append(cloned.recordOrder, owner)
			if sourceScope, ok := policy.recordPolicies[sourceOwner]; ok {
				cloned.recordPolicies[owner] = cloneCollectionPolicyScopeForInheritance(sourceScope)
			}
		}
	}
	return cloned
}