package configkit

import (
	"reflect"
	"strconv"

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

// Validation collects safe application diagnostics during a supported callback.
// A callback must not retain the context or use it concurrently.
type Validation struct {
	state *validationState
}

type validationState struct {
	active      bool
	errorCode   Code
	warningCode Code
	invalidPath Code
	schema      *schemaDescriptor
	document    *document.Node
	diagnostics []Diagnostic
}

// Error reports a value-free application error at path. Related paths are
// resolved to source locations when possible.
func (v *Validation) Error(path Path, message string, related ...Path) {
	v.report(SeverityError, path, message, related)
}

// Warning reports a value-free application warning at path. Related paths are
// resolved to source locations when possible.
func (v *Validation) Warning(path Path, message string, related ...Path) {
	v.report(SeverityWarning, path, message, related)
}

func (v *Validation) report(severity Severity, path Path, message string, related []Path) {
	if v == nil || v.state == nil || !v.state.active {
		panic(closedCallbackContextMessage)
	}
	code := v.state.errorCode
	if severity == SeverityWarning {
		code = v.state.warningCode
	}
	diagnostic := Diagnostic{Code: code, Severity: severity, Path: path.clone(), Message: message}
	if !path.valid() {
		invalidCode := v.state.invalidPath
		if invalidCode == "" {
			invalidCode = v.state.errorCode
		}
		diagnostic.Severity = SeverityError
		diagnostic.Code = invalidCode
		diagnostic.Path = Path{}
		diagnostic.Message = "application reported an invalid configuration path"
	} else if v.state.schema != nil {
		if _, ok := resolveSchemaPath(v.state.schema, path); !ok {
			diagnostic.Severity = SeverityError
			diagnostic.Code = v.state.invalidPath
			diagnostic.Message = "application reported a path outside the configuration schema"
			v.state.diagnostics = append(v.state.diagnostics, diagnostic)
			return
		}
		if location, ok := nearestDocumentLocation(v.state.document, path); ok {
			diagnostic.Primary = documentLocationPointer(location)
		}
	} else if location, ok := nearestDocumentLocation(v.state.document, path); ok {
		diagnostic.Primary = documentLocationPointer(location)
	}
	for _, relatedPath := range related {
		if !relatedPath.valid() {
			invalidCode := v.state.invalidPath
			if invalidCode == "" {
				invalidCode = v.state.errorCode
			}
			v.state.diagnostics = append(v.state.diagnostics, Diagnostic{
				Code: invalidCode, Severity: SeverityError,
				Message: "application reported an invalid related configuration path",
			})
			continue
		}
		if v.state.schema != nil {
			if _, ok := resolveSchemaPath(v.state.schema, relatedPath); !ok {
				v.state.diagnostics = append(v.state.diagnostics, Diagnostic{
					Code: v.state.invalidPath, Severity: SeverityError, Path: relatedPath.clone(),
					Message: "application reported a related path outside the configuration schema",
				})
				continue
			}
		}
		if location, ok := nearestDocumentLocation(v.state.document, relatedPath); ok {
			diagnostic.Related = append(diagnostic.Related, Location{
				SourceID: location.SourceID, Line: location.Line, Column: location.Column,
			})
		}
	}
	v.state.diagnostics = append(v.state.diagnostics, diagnostic)
}

func runValidation[T any](configuration *T, validator func(*T, *Validation), schema *schemaDescriptor, before, input *document.Node, lookups map[string]secretLookupResult) []Diagnostic {
	state := &validationState{
		active: true, errorCode: CodeValidateError, warningCode: CodeValidateWarning,
		invalidPath: CodeValidateInvalidPath, schema: schema, document: input,
	}
	context := &Validation{state: state}
	validator(configuration, context)
	state.active = false
	after, issue := projectConfiguration(schema, reflect.ValueOf(*configuration), defaultProjectionLimits())
	if issue != nil {
		state.diagnostics = append(state.diagnostics, validationMutationDiagnostic(issue.path))
		return canonicalDiagnostics(state.diagnostics)
	}
	state.diagnostics = append(state.diagnostics, validationValueMutations(before, after)...)
	for _, path := range changedSecretStates(reflect.ValueOf(*configuration), schema.root, lookups) {
		state.diagnostics = append(state.diagnostics, validationMutationDiagnostic(path))
	}
	return canonicalDiagnostics(state.diagnostics)
}

func validationMutationDiagnostic(path Path) Diagnostic {
	return Diagnostic{
		Code: CodeValidateMutation, Severity: SeverityError, Path: path.clone(),
		Message: "application validation mutated the configuration",
	}
}

func nearestDocumentLocation(root *document.Node, path Path) (document.Location, bool) {
	if root == nil || !path.valid() {
		return document.Location{}, false
	}
	current := root
	nearest := current.Location
	for _, segment := range path.segments {
		switch current.Kind {
		case document.Mapping:
			if segment.kind == pathSegmentIndex {
				return nearest, locationKnown(nearest)
			}
			found := false
			for _, entry := range current.Mapping {
				if entry.Key == segment.key {
					current = entry.Value
					nearest = current.Location
					found = true
					break
				}
			}
			if !found {
				return nearest, locationKnown(nearest)
			}
		case document.Sequence:
			index, ok := schemaIndex(segment)
			if !ok || index >= len(current.Sequence) {
				return nearest, locationKnown(nearest)
			}
			current = current.Sequence[index]
			nearest = current.Location
		default:
			return nearest, locationKnown(nearest)
		}
	}
	return nearest, locationKnown(nearest)
}

func locationKnown(location document.Location) bool {
	return location.SourceID != "" || location.Line != 0 || location.Column != 0
}

// validationValueMutations combines value and sensitivity changes; resolved
// secret state is audited separately because it never enters projected trees.
func validationValueMutations(before, after *document.Node) []Diagnostic {
	var diagnostics []Diagnostic
	for _, delta := range compareConfigurationValues(before, after) {
		diagnostics = append(diagnostics, validationMutationDiagnostic(delta.path))
	}
	beforeSensitivity := projectedSensitivity(before)
	afterSensitivity := projectedSensitivity(after)
	for pointer, path := range beforeSensitivity {
		if _, exists := afterSensitivity[pointer]; !exists {
			diagnostics = append(diagnostics, validationMutationDiagnostic(path))
		}
	}
	for pointer, path := range afterSensitivity {
		if _, exists := beforeSensitivity[pointer]; !exists {
			diagnostics = append(diagnostics, validationMutationDiagnostic(path))
		}
	}
	return diagnostics
}

func checkVersion(rule *VersionRule, root *document.Node) []Diagnostic {
	if rule == nil {
		return nil
	}
	version := Version{}
	node, present := documentAtPath(root, rule.Path)
	if present {
		version.Present = true
		switch node.Kind {
		case document.Null:
			version.Null = true
		case document.String:
			version.Text = node.Text
		case document.Number:
			if isIntegerVersion(node) {
				version.Text = node.Text
				break
			}
			fallthrough
		default:
			location, _ := nearestDocumentLocation(root, rule.Path)
			primary := documentLocationPointer(location)
			return []Diagnostic{{
				Code: CodeVersionType, Severity: SeverityError, Path: rule.Path.clone(),
				Message: "schema version must be a string, integer, or null", Primary: primary,
			}}
		}
	}
	state := &validationState{
		active: true, errorCode: CodeVersionError, warningCode: CodeVersionWarning,
		invalidPath: CodeVersionError, document: root,
	}
	validation := &Validation{state: state}
	err := rule.Check(version, validation)
	state.active = false
	if err != nil && !hasErrors(state.diagnostics) {
		location, _ := nearestDocumentLocation(root, rule.Path)
		state.diagnostics = append(state.diagnostics, Diagnostic{
			Code: CodeVersionHookFailed, Severity: SeverityError, Path: rule.Path.clone(),
			Message: "schema-version check failed", Primary: documentLocationPointer(location),
		})
	}
	return canonicalDiagnostics(state.diagnostics)
}

func isIntegerVersion(node *document.Node) bool {
	return node != nil && node.Kind == document.Number && integerPattern.MatchString(node.Text)
}

func pathMatches(configured *Path, current Path) bool {
	if configured == nil || !configured.valid() || !current.valid() || len(configured.segments) != len(current.segments) {
		return false
	}
	for i, expected := range configured.segments {
		actual := current.segments[i]
		if expected.kind == pathSegmentParsed {
			if actual.kind == pathSegmentIndex {
				if expected.key != strconv.Itoa(actual.index) {
					return false
				}
			} else if expected.key != actual.key {
				return false
			}
			continue
		}
		if expected.kind != actual.kind || expected.key != actual.key || expected.index != actual.index {
			return false
		}
	}
	return true
}

func documentLocationPointer(location document.Location) *Location {
	if !locationKnown(location) {
		return nil
	}
	return &Location{SourceID: location.SourceID, Line: location.Line, Column: location.Column}
}