package artifactpolicy

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

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
}

// 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)
}

// 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)
}