package diagnostics

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"gitea.maximumdirect.net/eric/notarius/internal/core/artifacts"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
)

const defaultWorkDir = "/tmp/notarius"

// RunDirectory represents a per-run diagnostics directory.
type RunDirectory struct {
	path      string
	retention RetentionMode
	createdAt time.Time
}

type RetentionMode string

const (
	RetentionAuto   RetentionMode = "auto"
	RetentionAlways RetentionMode = "always"
	RetentionNever  RetentionMode = "never"
)

type RetentionDecisionInput struct {
	RetentionMode RetentionMode
	RunSucceeded  bool
	HasWarnings   bool
}

// InvocationMetadata captures non-secret invocation details for diagnostics.
type InvocationMetadata struct {
	Operation      string    `json:"operation"`
	PipelineID     string    `json:"pipeline_id,omitempty"`
	PipelineDigest string    `json:"pipeline_digest,omitempty"`
	InputPath      string    `json:"input_path,omitempty"`
	ConfigPath     string    `json:"config_path,omitempty"`
	ConfigSource   string    `json:"config_source,omitempty"`
	OnlyLanes      []string  `json:"only_lanes,omitempty"`
	RunID          string    `json:"run_id"`
	StartedAt      time.Time `json:"started_at"`
}

func ShouldRetainRunDirectory(input RetentionDecisionInput) bool {
	if !input.RunSucceeded {
		return true
	}

	switch input.RetentionMode {
	case RetentionAlways:
		return true
	case RetentionNever:
		return false
	case RetentionAuto, "":
		return input.HasWarnings
	default:
		return true
	}
}

func NewRunDirectory(workDir string, retention RetentionMode) (*RunDirectory, error) {
	if strings.TrimSpace(workDir) == "" {
		workDir = defaultWorkDir
	}
	if retention == "" {
		retention = RetentionAuto
	}

	if err := os.MkdirAll(workDir, 0o755); err != nil {
		return nil, fmt.Errorf("create diagnostics work directory %q: %w", workDir, err)
	}

	createdAt := time.Now().UTC()
	runID := fmt.Sprintf("run-%d", createdAt.UnixNano())
	runPath := filepath.Join(workDir, runID)
	if err := os.Mkdir(runPath, 0o755); err != nil {
		return nil, fmt.Errorf("create diagnostics run directory %q: %w", runPath, err)
	}

	return &RunDirectory{
		path:      runPath,
		retention: retention,
		createdAt: createdAt,
	}, nil
}

func (r *RunDirectory) Path() string {
	if r == nil {
		return ""
	}
	return r.path
}

func (r *RunDirectory) RunID() string {
	if r == nil {
		return ""
	}
	return filepath.Base(r.path)
}

func (r *RunDirectory) WriteInvocationMetadata(metadata InvocationMetadata) error {
	if r == nil {
		return fmt.Errorf("run directory must not be nil")
	}
	if metadata.RunID == "" {
		metadata.RunID = r.RunID()
	}
	if metadata.StartedAt.IsZero() {
		metadata.StartedAt = r.createdAt
	}
	return r.WriteJSONArtifact(ArtifactInvocationMetadata, metadata)
}

func (r *RunDirectory) WriteRedactedEffectiveConfig(payload any) error {
	return r.WriteJSONArtifact(ArtifactEffectiveConfig, payload)
}

func (r *RunDirectory) WriteResolvedPipeline(payload any) error {
	return r.WriteJSONArtifact(ArtifactResolvedPipeline, payload)
}

func (r *RunDirectory) WriteSourceDocument(payload any) error {
	return r.WriteJSONArtifact(ArtifactSourceDocument, payload)
}

func (r *RunDirectory) WriteRunManifest(manifest artifacts.RunManifest) error {
	return r.WriteJSONArtifact(ArtifactRunManifest, manifest)
}

func (r *RunDirectory) WriteRunReport(payload any) error {
	return r.WriteJSONArtifact(ArtifactRunReport, payload)
}

func (r *RunDirectory) WriteWarnings(warnings []contracts.Warning) error {
	return r.WriteJSONArtifact(ArtifactWarnings, warnings)
}

func (r *RunDirectory) WriteErrorLog(errorMessage string) error {
	if r == nil {
		return fmt.Errorf("run directory must not be nil")
	}
	path, err := r.artifactPath(ArtifactErrorLog)
	if err != nil {
		return err
	}
	if err := os.WriteFile(path, []byte(errorMessage+"\n"), 0o644); err != nil {
		return fmt.Errorf("write diagnostics artifact %q: %w", ArtifactErrorLog, err)
	}
	return nil
}

func (r *RunDirectory) WriteJSONArtifact(name string, payload any) error {
	if r == nil {
		return fmt.Errorf("run directory must not be nil")
	}
	path, err := r.artifactPath(name)
	if err != nil {
		return err
	}

	data, err := json.MarshalIndent(payload, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal diagnostics artifact %q: %w", name, err)
	}
	data = append(data, '\n')
	if err := os.WriteFile(path, data, 0o644); err != nil {
		return fmt.Errorf("write diagnostics artifact %q: %w", name, err)
	}
	return nil
}

func (r *RunDirectory) ApplyRetention(input RetentionDecisionInput) error {
	if r == nil {
		return fmt.Errorf("run directory must not be nil")
	}
	decision := input
	if decision.RetentionMode == "" {
		decision.RetentionMode = r.retention
	}
	if ShouldRetainRunDirectory(decision) {
		return nil
	}
	if err := os.RemoveAll(r.path); err != nil {
		return fmt.Errorf("remove diagnostics run directory %q: %w", r.path, err)
	}
	return nil
}

func (r *RunDirectory) artifactPath(name string) (string, error) {
	name = strings.TrimSpace(name)
	if name == "" {
		return "", fmt.Errorf("diagnostics artifact name must not be empty")
	}
	if filepath.IsAbs(name) {
		return "", fmt.Errorf("diagnostics artifact name %q must not be absolute", name)
	}
	if name != filepath.Base(name) || strings.Contains(name, "/") || strings.Contains(name, `\`) {
		return "", fmt.Errorf("diagnostics artifact name %q must not contain path separators", name)
	}

	runPath, err := filepath.Abs(r.path)
	if err != nil {
		return "", fmt.Errorf("resolve diagnostics run directory %q: %w", r.path, err)
	}
	artifactPath, err := filepath.Abs(filepath.Join(runPath, name))
	if err != nil {
		return "", fmt.Errorf("resolve diagnostics artifact %q: %w", name, err)
	}
	if filepath.Dir(artifactPath) != runPath {
		return "", fmt.Errorf("diagnostics artifact name %q resolves outside run directory", name)
	}
	return artifactPath, nil
}