package artifactpolicy

import (
	"errors"
	"fmt"
	"regexp"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/artifactmodel"
	"gitea.maximumdirect.net/eric/narratio/internal/pathsafe"
)

const (
	SourceBoundsSession = "narratio.bounds.session"

	configuredSourcePrefix      = "narratio.artifact."
	previousConfiguredSrcPrefix = "narratio.previous_session.artifact."
)

var configuredSourceRE = regexp.MustCompile(`^narratio\.artifact\.([a-z][a-z0-9_]*)$`)
var previousSourceRE = regexp.MustCompile(`^narratio\.previous_session\.artifact\.([a-z][a-z0-9_]*)$`)

var (
	ErrUnsupportedScriptoriumInputSource = errors.New("unsupported scriptorium input source")
	ErrInvalidPreviousSessionSource      = errors.New("invalid previous-session source format")
)

type SourceKind string

const (
	SourceKindBuiltIn            SourceKind = "built_in"
	SourceKindConfiguredArtifact SourceKind = "configured_artifact"
	SourceKindPreviousArtifact   SourceKind = "previous_session_configured_artifact"
)

// Source describes one normalized artifact source identifier.
type Source struct {
	ID            string
	Kind          SourceKind
	ConfiguredKey string
}

// ScriptoriumInputSourceDescriptor describes one validated Scriptorium input source.
type ScriptoriumInputSourceDescriptor struct {
	Source          Source
	PreviousSession *PreviousSessionSourceDescriptor
}

// PreviousSessionSourceDescriptor describes one canonical previous-session input source.
type PreviousSessionSourceDescriptor struct {
	SourceID           string
	ConfiguredKey      string
	ConfiguredSourceID string
}

// UnknownConfiguredArtifactError reports a source that references an undefined configured artifact key.
type UnknownConfiguredArtifactError struct {
	ConfiguredKey string
}

func (e *UnknownConfiguredArtifactError) Error() string {
	return fmt.Sprintf("references unknown artifact %q", e.ConfiguredKey)
}

// ConfiguredSourceID converts a configured artifact key into source id form.
func ConfiguredSourceID(key string) string {
	return configuredSourcePrefix + strings.TrimSpace(key)
}

// PreviousSessionSourceID converts a configured artifact key into previous-session source id form.
func PreviousSessionSourceID(key string) string {
	return previousConfiguredSrcPrefix + strings.TrimSpace(key)
}

// ParseConfiguredSource extracts configured key from narratio.artifact.<key>.
func ParseConfiguredSource(source string) (string, bool) {
	matches := configuredSourceRE.FindStringSubmatch(strings.TrimSpace(source))
	if len(matches) != 2 {
		return "", false
	}
	return matches[1], true
}

// ParsePreviousSessionSource extracts configured key from narratio.previous_session.artifact.<key>.
func ParsePreviousSessionSource(source string) (string, bool) {
	matches := previousSourceRE.FindStringSubmatch(strings.TrimSpace(source))
	if len(matches) != 2 {
		return "", false
	}
	return matches[1], true
}

// ClassifySource classifies a source id as built-in, configured, or previous-session configured.
func ClassifySource(source string) (Source, error) {
	trimmed := strings.TrimSpace(source)
	if trimmed == "" {
		return Source{}, fmt.Errorf("artifact source is required")
	}
	if _, ok := artifactmodel.LookupRuntimeTranscriptArtifact(trimmed); ok {
		return Source{ID: trimmed, Kind: SourceKindBuiltIn}, nil
	}
	if trimmed == SourceBoundsSession {
		return Source{ID: trimmed, Kind: SourceKindBuiltIn}, nil
	}
	if key, ok := ParseConfiguredSource(trimmed); ok {
		return Source{ID: trimmed, Kind: SourceKindConfiguredArtifact, ConfiguredKey: key}, nil
	}
	if key, ok := ParsePreviousSessionSource(trimmed); ok {
		return Source{ID: trimmed, Kind: SourceKindPreviousArtifact, ConfiguredKey: key}, nil
	}
	return Source{}, fmt.Errorf("unsupported artifact source %q", source)
}

// DescribeScriptoriumInputSource classifies one input source and returns descriptor
// metadata used by config validation, analyze input resolution, and previous-cache planning.
func DescribeScriptoriumInputSource(source string) (ScriptoriumInputSourceDescriptor, error) {
	trimmed := strings.TrimSpace(source)
	if trimmed == "" {
		return ScriptoriumInputSourceDescriptor{}, ErrUnsupportedScriptoriumInputSource
	}
	if strings.HasPrefix(trimmed, "narratio.previous_session.artifact") {
		descriptor, err := DescribePreviousSessionSource(trimmed)
		if err != nil {
			return ScriptoriumInputSourceDescriptor{}, err
		}
		return ScriptoriumInputSourceDescriptor{
			Source: Source{
				ID:            descriptor.SourceID,
				Kind:          SourceKindPreviousArtifact,
				ConfiguredKey: descriptor.ConfiguredKey,
			},
			PreviousSession: &descriptor,
		}, nil
	}

	classified, err := ClassifySource(trimmed)
	if err != nil {
		return ScriptoriumInputSourceDescriptor{}, ErrUnsupportedScriptoriumInputSource
	}
	return ScriptoriumInputSourceDescriptor{Source: classified}, nil
}

// DescribePreviousSessionSource validates a canonical previous-session source id
// and returns both previous and configured-source vocabulary descriptors.
func DescribePreviousSessionSource(source string) (PreviousSessionSourceDescriptor, error) {
	configuredKey, ok := ParsePreviousSessionSource(source)
	if !ok {
		return PreviousSessionSourceDescriptor{}, ErrInvalidPreviousSessionSource
	}
	return PreviousSessionSourceDescriptor{
		SourceID:           PreviousSessionSourceID(configuredKey),
		ConfiguredKey:      configuredKey,
		ConfiguredSourceID: ConfiguredSourceID(configuredKey),
	}, nil
}

// PreviousSessionSourceDescriptorForConfiguredKey derives a previous-session source descriptor
// from a configured artifact key.
func PreviousSessionSourceDescriptorForConfiguredKey(configuredKey string) (PreviousSessionSourceDescriptor, error) {
	return DescribePreviousSessionSource(PreviousSessionSourceID(configuredKey))
}

// ValidateInputConfiguredReference checks that configured/previous-session sources
// reference configured artifacts known to the current Scriptorium config.
func ValidateInputConfiguredReference(
	descriptor ScriptoriumInputSourceDescriptor,
	configured map[string]struct{},
) error {
	switch descriptor.Source.Kind {
	case SourceKindConfiguredArtifact, SourceKindPreviousArtifact:
		if _, ok := configured[descriptor.Source.ConfiguredKey]; !ok {
			return &UnknownConfiguredArtifactError{ConfiguredKey: descriptor.Source.ConfiguredKey}
		}
	}
	return nil
}

// ValidatePublishSource validates that a source is publish-compatible and references a known configured artifact.
func ValidatePublishSource(source string, configured map[string]string) (Source, error) {
	classified, err := ClassifySource(source)
	if err != nil {
		return Source{}, fmt.Errorf("must be a built-in source id or narratio.artifact.<name>")
	}
	if classified.Kind == SourceKindPreviousArtifact {
		return Source{}, fmt.Errorf("must be a built-in source id or narratio.artifact.<name>")
	}
	if classified.Kind == SourceKindConfiguredArtifact {
		if configured == nil {
			return Source{}, fmt.Errorf("configured artifact %q is not defined in pipeline.scriptorium.artifacts", classified.ConfiguredKey)
		}
		if _, ok := configured[classified.ConfiguredKey]; !ok {
			return Source{}, fmt.Errorf("configured artifact %q is not defined in pipeline.scriptorium.artifacts", classified.ConfiguredKey)
		}
	}
	return classified, nil
}

// DeriveDefaultPublishedDestination returns the default publish destination for one source.
func DeriveDefaultPublishedDestination(source Source, configured map[string]string) (string, error) {
	switch source.Kind {
	case SourceKindBuiltIn:
		if spec, ok := artifactmodel.LookupRuntimeTranscriptArtifact(source.ID); ok {
			return pathsafe.NormalizeRelativeDestination(spec.CanonicalRelPath)
		}
		if source.ID == SourceBoundsSession {
			return pathsafe.NormalizeRelativeDestination("artifacts/session_bounds.json")
		}
		return "", fmt.Errorf("unsupported built-in source %q", source.ID)
	case SourceKindConfiguredArtifact:
		if configured == nil {
			return "", fmt.Errorf("configured artifact %q is not defined in pipeline.scriptorium.artifacts", source.ConfiguredKey)
		}
		outputPath, ok := configured[source.ConfiguredKey]
		if !ok {
			return "", fmt.Errorf("configured artifact %q is not defined in pipeline.scriptorium.artifacts", source.ConfiguredKey)
		}
		if strings.TrimSpace(outputPath) == "" {
			return "", fmt.Errorf("pipeline.scriptorium.artifacts.%s.output_path is empty", source.ConfiguredKey)
		}
		return pathsafe.NormalizeRelativeDestination(outputPath)
	default:
		return "", fmt.Errorf("publish destination cannot be derived from source %q", source.ID)
	}
}

// ResolvePublishedDestination validates and normalizes an explicit destination,
// or derives one when omitted.
func ResolvePublishedDestination(sourceID, explicitDest string, configured map[string]string) (string, error) {
	source, err := ValidatePublishSource(sourceID, configured)
	if err != nil {
		return "", err
	}
	if strings.TrimSpace(explicitDest) != "" {
		return pathsafe.NormalizeRelativeDestination(explicitDest)
	}
	return DeriveDefaultPublishedDestination(source, configured)
}