package state

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

	"gitea.maximumdirect.net/eric/weatherreporter/internal/config"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/fileutil"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/module"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/promptinput"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
)

type FilesystemStore struct {
	root             string
	snapshotsDir     string
	reportsDir       string
	dataPackagesDir  string
	preflightDir     string
	notificationsDir string
}

type ArtifactPaths struct {
	ModuleSnapshot   string `json:"moduleSnapshot"`
	Metadata         string `json:"metadata"`
	DataPackage      string `json:"dataPackage"`
	Preparation      string `json:"preparation,omitempty"`
	Execution        string `json:"execution,omitempty"`
	Notification     string `json:"notification,omitempty"`
	RenderedReport   string `json:"renderedReport,omitempty"`
	GeneratedTextRaw string `json:"generatedTextRaw,omitempty"`
	GeneratedText    string `json:"generatedText,omitempty"`
	RenderContext    string `json:"renderContext,omitempty"`
}

type ReportRecord struct {
	RunID        string    `json:"runId"`
	ReportID     report.ID `json:"reportId"`
	Variant      string    `json:"variant,omitempty"`
	PromptID     string    `json:"promptId"`
	GeneratedAt  string    `json:"generatedAt"`
	ValidStart   string    `json:"validStart"`
	ValidEnd     string    `json:"validEnd"`
	MetadataPath string    `json:"metadataPath"`
	ReportPath   string    `json:"reportPath,omitempty"`
	Warnings     int       `json:"warnings"`
	metadata     Metadata
}

func NewFilesystemStore(cfg config.WorkspaceConfig) (*FilesystemStore, error) {
	if cfg.Root == "" {
		return nil, fmt.Errorf("workspace root is required")
	}
	for name, value := range map[string]string{
		"snapshots_dir":     cfg.SnapshotsDir,
		"reports_dir":       cfg.ReportsDir,
		"data_packages_dir": cfg.DataPackagesDir,
		"preflight_dir":     cfg.PreflightDir,
		"notifications_dir": cfg.NotificationsDir,
	} {
		if err := validateRelativeDir(name, value); err != nil {
			return nil, err
		}
	}
	return &FilesystemStore{
		root:             filepath.Clean(cfg.Root),
		snapshotsDir:     filepath.Clean(cfg.SnapshotsDir),
		reportsDir:       filepath.Clean(cfg.ReportsDir),
		dataPackagesDir:  filepath.Clean(cfg.DataPackagesDir),
		preflightDir:     filepath.Clean(cfg.PreflightDir),
		notificationsDir: filepath.Clean(cfg.NotificationsDir),
	}, nil
}

func (s *FilesystemStore) Paths(resolved report.Resolved) (ArtifactPaths, error) {
	if s == nil {
		return ArtifactPaths{}, fmt.Errorf("state store is required")
	}
	metadata := resolved.Metadata()
	if err := validatePathSegment("run id", metadata.RunID); err != nil {
		return ArtifactPaths{}, err
	}
	group := resolved.Definition.ArtifactGroup
	if group == "" {
		return ArtifactPaths{}, fmt.Errorf("report %q has no artifact group", resolved.Definition.ID)
	}
	validDate := resolved.ValidPeriod.Start.Format("2006-01-02")
	return ArtifactPaths{
		ModuleSnapshot:   s.join(s.snapshotsDir, group, validDate, "modules."+metadata.RunID+".json"),
		Metadata:         s.join(s.snapshotsDir, group, validDate, "metadata."+metadata.RunID+".json"),
		DataPackage:      s.join(s.dataPackagesDir, group, validDate, "data_package."+metadata.RunID+".yaml"),
		Preparation:      s.join(s.preflightDir, group, validDate, "prompt_preparation."+metadata.RunID+".json"),
		Execution:        s.join(s.snapshotsDir, group, validDate, "prompt_execution."+metadata.RunID+".json"),
		Notification:     s.join(s.notificationsDir, group, validDate, "distributor."+metadata.RunID+".json"),
		RenderedReport:   s.join(s.reportsDir, group, validDate, "report."+metadata.RunID+".md"),
		GeneratedTextRaw: s.join(s.snapshotsDir, group, validDate, "generated_text_raw."+metadata.RunID+".json"),
		GeneratedText:    s.join(s.snapshotsDir, group, validDate, "generated_text."+metadata.RunID+".json"),
		RenderContext:    s.join(s.snapshotsDir, group, validDate, "render_context."+metadata.RunID+".json"),
	}, nil
}

func (s *FilesystemStore) SaveModuleSnapshot(_ context.Context, resolved report.Resolved, snapshot module.Snapshot) (string, error) {
	if err := snapshot.Validate(); err != nil {
		return "", err
	}
	return s.saveResolvedJSON(resolved, func(paths ArtifactPaths) string {
		return paths.ModuleSnapshot
	}, snapshot)
}

func (s *FilesystemStore) SaveDataPackage(ctx context.Context, resolved report.Resolved, pkg promptinput.Package) (string, error) {
	data, err := promptinput.MarshalYAML(pkg)
	if err != nil {
		return "", err
	}
	return s.SaveDataPackageBytes(ctx, resolved, data)
}

func (s *FilesystemStore) SaveDataPackageBytes(_ context.Context, resolved report.Resolved, data []byte) (string, error) {
	paths, err := s.Paths(resolved)
	if err != nil {
		return "", err
	}
	if err := fileutil.WriteFileAtomic(paths.DataPackage, data); err != nil {
		return "", err
	}
	return paths.DataPackage, nil
}

func (s *FilesystemStore) SavePromptPreparation(_ context.Context, resolved report.Resolved, artifact PromptPreparationArtifact) (string, error) {
	if artifact.SchemaVersion == "" {
		artifact.SchemaVersion = PromptPreparationSchemaVersion
	}
	if err := artifact.Validate(); err != nil {
		return "", err
	}
	return s.saveResolvedJSON(resolved, func(paths ArtifactPaths) string {
		return paths.Preparation
	}, artifact)
}

func (s *FilesystemStore) SavePromptExecution(_ context.Context, resolved report.Resolved, artifact PromptExecutionArtifact) (string, error) {
	if artifact.SchemaVersion == "" {
		artifact.SchemaVersion = PromptExecutionSchemaVersion
	}
	if err := artifact.Validate(); err != nil {
		return "", err
	}
	return s.saveResolvedJSON(resolved, func(paths ArtifactPaths) string {
		return paths.Execution
	}, artifact)
}

func (s *FilesystemStore) SaveDistributorNotification(_ context.Context, resolved report.Resolved, artifact DistributorNotificationArtifact) (string, error) {
	if artifact.SchemaVersion == "" {
		artifact.SchemaVersion = DistributorNotificationSchemaVersion
	}
	return s.saveResolvedJSON(resolved, func(paths ArtifactPaths) string {
		return paths.Notification
	}, artifact)
}

func (s *FilesystemStore) BatchDistributorNotificationPath(ref BatchDistributorNotificationRef) (string, error) {
	if s == nil {
		return "", fmt.Errorf("state store is required")
	}
	if err := validateBatchNotificationRef(ref); err != nil {
		return "", err
	}
	localDate := ref.StartedAt.In(ref.Location).Format("2006-01-02")
	return s.join(s.notificationsDir, "batches", ref.Batch, localDate, "distributor."+ref.BatchRunID+".json"), nil
}

func (s *FilesystemStore) SaveBatchDistributorNotification(_ context.Context, ref BatchDistributorNotificationRef, artifact BatchDistributorNotificationArtifact) (string, error) {
	path, err := s.BatchDistributorNotificationPath(ref)
	if err != nil {
		return "", err
	}
	if artifact.SchemaVersion == "" {
		artifact.SchemaVersion = BatchDistributorNotificationSchemaVersion
	}
	artifact.Batch = ref.Batch
	artifact.BatchRunID = ref.BatchRunID
	if err := fileutil.WriteJSONAtomic(path, artifact); err != nil {
		return "", err
	}
	return path, nil
}

func (s *FilesystemStore) SaveGeneratedTextRaw(_ context.Context, resolved report.Resolved, data []byte) (string, error) {
	return s.saveResolvedBytes(resolved, func(paths ArtifactPaths) string {
		return paths.GeneratedTextRaw
	}, data)
}

func (s *FilesystemStore) SaveGeneratedText(_ context.Context, resolved report.Resolved, data []byte) (string, error) {
	return s.saveResolvedBytes(resolved, func(paths ArtifactPaths) string {
		return paths.GeneratedText
	}, data)
}

func (s *FilesystemStore) SaveRenderContext(_ context.Context, resolved report.Resolved, value any) (string, error) {
	return s.saveResolvedJSON(resolved, func(paths ArtifactPaths) string {
		return paths.RenderContext
	}, value)
}

func (s *FilesystemStore) saveResolvedJSON(resolved report.Resolved, selectPath func(ArtifactPaths) string, value any) (string, error) {
	paths, err := s.Paths(resolved)
	if err != nil {
		return "", err
	}
	path := selectPath(paths)
	if err := fileutil.WriteJSONAtomic(path, value); err != nil {
		return "", err
	}
	return path, nil
}

func (s *FilesystemStore) saveResolvedBytes(resolved report.Resolved, selectPath func(ArtifactPaths) string, data []byte) (string, error) {
	paths, err := s.Paths(resolved)
	if err != nil {
		return "", err
	}
	path := selectPath(paths)
	if err := fileutil.WriteFileAtomic(path, data); err != nil {
		return "", err
	}
	return path, nil
}

func (s *FilesystemStore) PrepareRenderedReport(_ context.Context, resolved report.Resolved) (string, error) {
	paths, err := s.Paths(resolved)
	if err != nil {
		return "", err
	}
	if err := os.MkdirAll(filepath.Dir(paths.RenderedReport), 0o755); err != nil {
		return "", fmt.Errorf("create rendered report directory %q: %w", filepath.Dir(paths.RenderedReport), err)
	}
	return paths.RenderedReport, nil
}

func (s *FilesystemStore) SaveMetadata(_ context.Context, metadata Metadata) (string, error) {
	if metadata.SchemaVersion != MetadataSchemaVersion {
		return "", fmt.Errorf("new metadata must use schema version %q", MetadataSchemaVersion)
	}
	if err := metadata.Validate(); err != nil {
		return "", err
	}
	if err := s.validateManagedPath("metadata path", metadata.MetadataPath); err != nil {
		return "", err
	}
	if err := fileutil.WriteJSONAtomic(metadata.MetadataPath, metadata); err != nil {
		return "", err
	}
	return metadata.MetadataPath, nil
}

func (s *FilesystemStore) FindPriorSnapshot(_ context.Context, resolved report.Resolved) (*PriorSnapshot, error) {
	if resolved.Definition.ComparisonStrategy != report.CompareSameValidDate {
		return nil, nil
	}
	group := resolved.Definition.ArtifactGroup
	if group == "" {
		return nil, fmt.Errorf("report %q has no artifact group", resolved.Definition.ID)
	}
	dirs, err := s.metadataDirectories(resolved, group)
	if err != nil {
		return nil, err
	}

	var candidates []Metadata
	for _, dir := range dirs {
		entries, err := os.ReadDir(dir)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			}
			return nil, fmt.Errorf("read snapshot metadata directory %q: %w", dir, err)
		}
		for _, entry := range entries {
			if entry.IsDir() || !isMetadataFilename(entry.Name()) {
				continue
			}
			path := filepath.Join(dir, entry.Name())
			var metadata Metadata
			if err := readJSON(path, &metadata); err != nil {
				return nil, err
			}
			if metadata.RunID == resolved.Metadata().RunID {
				continue
			}
			if !resolved.Definition.CompatibleWithPrior(metadata.ReportID) {
				continue
			}
			if !comparablePeriod(metadata, resolved) {
				continue
			}
			if !metadata.GeneratedAt.Before(resolved.GeneratedAt) {
				continue
			}
			candidates = append(candidates, metadata)
		}
	}
	if len(candidates) == 0 {
		return nil, nil
	}
	sort.Slice(candidates, func(i, j int) bool {
		return candidates[i].GeneratedAt.After(candidates[j].GeneratedAt)
	})
	return &PriorSnapshot{
		Metadata:           candidates[0],
		ModuleSnapshotPath: candidates[0].ModuleSnapshotPath,
	}, nil
}

func (s *FilesystemStore) ListReports(_ context.Context, limit int) ([]ReportRecord, error) {
	if s == nil {
		return nil, fmt.Errorf("state store is required")
	}
	root := s.join(s.snapshotsDir)
	if _, err := os.Stat(root); err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("inspect %q: %w", root, err)
	}
	var records []ReportRecord
	err := filepath.WalkDir(root, func(path string, entry os.DirEntry, err error) error {
		if err != nil {
			return fmt.Errorf("inspect %q: %w", path, err)
		}
		if entry.IsDir() || !isMetadataFilename(entry.Name()) {
			return nil
		}
		record, err := s.reportRecord(path)
		if err != nil {
			return err
		}
		records = append(records, record)
		return nil
	})
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	sort.Slice(records, func(i, j int) bool {
		return records[i].metadata.GeneratedAt.After(records[j].metadata.GeneratedAt)
	})
	if limit > 0 && len(records) > limit {
		records = records[:limit]
	}
	return records, nil
}

func (s *FilesystemStore) LoadMetadataByRunID(ctx context.Context, runID string) (Metadata, string, error) {
	if strings.TrimSpace(runID) == "" {
		return Metadata{}, "", fmt.Errorf("run id is required")
	}
	records, err := s.ListReports(ctx, 0)
	if err != nil {
		return Metadata{}, "", err
	}
	for _, record := range records {
		if record.RunID == runID {
			return record.metadata, record.MetadataPath, nil
		}
	}
	return Metadata{}, "", fmt.Errorf("metadata for run id %q was not found", runID)
}

func (s *FilesystemStore) LoadDataPackage(_ context.Context, path string) (promptinput.Package, error) {
	if path == "" {
		return promptinput.Package{}, fmt.Errorf("data package path is required")
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return promptinput.Package{}, fmt.Errorf("read %q: %w", path, err)
	}
	pkg, err := promptinput.LoadYAML(data)
	if err != nil {
		return promptinput.Package{}, err
	}
	return pkg, nil
}

func (s *FilesystemStore) LoadModuleSnapshot(_ context.Context, path string) (module.Snapshot, error) {
	if path == "" {
		return module.Snapshot{}, fmt.Errorf("module snapshot path is required")
	}
	var snapshot module.Snapshot
	if err := readJSON(path, &snapshot); err != nil {
		return module.Snapshot{}, err
	}
	if err := snapshot.Validate(); err != nil {
		return module.Snapshot{}, err
	}
	return snapshot, nil
}

func (s *FilesystemStore) LoadGeneratedText(_ context.Context, path string) ([]byte, error) {
	if path == "" {
		return nil, fmt.Errorf("generated text path is required")
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read %q: %w", path, err)
	}
	return data, nil
}

func (s *FilesystemStore) LoadPromptPreparation(_ context.Context, path string) (PromptPreparationArtifact, error) {
	if path == "" {
		return PromptPreparationArtifact{}, fmt.Errorf("prompt preparation path is required")
	}
	var artifact PromptPreparationArtifact
	if err := readJSON(path, &artifact); err != nil {
		return PromptPreparationArtifact{}, err
	}
	if err := artifact.Validate(); err != nil {
		return PromptPreparationArtifact{}, err
	}
	return artifact, nil
}

func (s *FilesystemStore) LoadPromptExecution(_ context.Context, path string) (PromptExecutionArtifact, error) {
	if path == "" {
		return PromptExecutionArtifact{}, fmt.Errorf("prompt execution path is required")
	}
	var artifact PromptExecutionArtifact
	if err := readJSON(path, &artifact); err != nil {
		return PromptExecutionArtifact{}, err
	}
	if err := artifact.Validate(); err != nil {
		return PromptExecutionArtifact{}, err
	}
	return artifact, nil
}

func (s *FilesystemStore) LoadRenderContext(_ context.Context, path string, target any) error {
	if path == "" {
		return fmt.Errorf("render context path is required")
	}
	if target == nil {
		return fmt.Errorf("render context target is required")
	}
	return readJSON(path, target)
}

func (s *FilesystemStore) reportRecord(path string) (ReportRecord, error) {
	var metadata Metadata
	if err := readJSON(path, &metadata); err != nil {
		return ReportRecord{}, err
	}
	metadata.MetadataPath = path
	return ReportRecord{
		RunID:        metadata.RunID,
		ReportID:     metadata.ReportID,
		Variant:      metadata.Variant,
		PromptID:     metadata.PromptID,
		GeneratedAt:  metadata.GeneratedAt.Format(time.RFC3339Nano),
		ValidStart:   metadata.ValidPeriod.Start.Format(time.RFC3339Nano),
		ValidEnd:     metadata.ValidPeriod.End.Format(time.RFC3339Nano),
		MetadataPath: path,
		ReportPath:   metadata.RenderedReportPath,
		Warnings:     len(metadata.SourceWarnings),
		metadata:     metadata,
	}, nil
}

func (s *FilesystemStore) metadataDirectories(resolved report.Resolved, group string) ([]string, error) {
	paths, err := s.Paths(resolved)
	if err != nil {
		return nil, err
	}
	return []string{filepath.Dir(paths.Metadata)}, nil
}

func (s *FilesystemStore) join(parts ...string) string {
	all := append([]string{s.root}, parts...)
	return filepath.Join(all...)
}

func (s *FilesystemStore) validateManagedPath(name, path string) error {
	if s == nil {
		return fmt.Errorf("state store is required")
	}
	root, err := filepath.Abs(s.root)
	if err != nil {
		return fmt.Errorf("resolve workspace root: %w", err)
	}
	target, err := filepath.Abs(path)
	if err != nil {
		return fmt.Errorf("resolve %s: %w", name, err)
	}
	relative, err := filepath.Rel(root, target)
	if err != nil {
		return fmt.Errorf("resolve %s relative to workspace root: %w", name, err)
	}
	if relative == "." || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
		return fmt.Errorf("%s must stay within workspace root", name)
	}
	return nil
}

func validateRelativeDir(name string, value string) error {
	if value == "" {
		return fmt.Errorf("%s is required", name)
	}
	if filepath.IsAbs(value) {
		return fmt.Errorf("%s must be relative to workspace root", name)
	}
	cleaned := filepath.Clean(value)
	if cleaned == "." || cleaned == ".." || strings.HasPrefix(cleaned, ".."+string(filepath.Separator)) {
		return fmt.Errorf("%s must stay within workspace root", name)
	}
	return nil
}

func validateBatchNotificationRef(ref BatchDistributorNotificationRef) error {
	if err := validatePathSegment("batch kind", ref.Batch); err != nil {
		return err
	}
	if err := validatePathSegment("batch run id", ref.BatchRunID); err != nil {
		return err
	}
	if ref.StartedAt.IsZero() {
		return fmt.Errorf("batch started time is required")
	}
	if ref.Location == nil {
		return fmt.Errorf("batch location is required")
	}
	return nil
}

func validatePathSegment(name string, value string) error {
	if strings.TrimSpace(value) == "" {
		return fmt.Errorf("%s is required", name)
	}
	if strings.ContainsAny(value, `/\`) {
		return fmt.Errorf("%s must not contain path separators", name)
	}
	if value == "." || value == ".." {
		return fmt.Errorf("%s must be a safe path segment", name)
	}
	return nil
}

func isMetadataFilename(name string) bool {
	if !strings.HasPrefix(name, "metadata.") || !strings.HasSuffix(name, ".json") {
		return false
	}
	runID := strings.TrimSuffix(strings.TrimPrefix(name, "metadata."), ".json")
	return strings.TrimSpace(runID) != "" && !strings.ContainsAny(runID, `/\`) && runID != "." && runID != ".."
}

func readJSON(path string, target any) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("read %q: %w", path, err)
	}
	if err := json.Unmarshal(data, target); err != nil {
		return fmt.Errorf("decode %q: %w", path, err)
	}
	return nil
}

func sameValidDate(metadata Metadata, resolved report.Resolved) bool {
	return metadata.ValidPeriod.Start.Format("2006-01-02") == resolved.ValidPeriod.Start.Format("2006-01-02")
}

func comparablePeriod(metadata Metadata, resolved report.Resolved) bool {
	return resolved.Definition.ComparisonStrategy == report.CompareSameValidDate && sameValidDate(metadata, resolved)
}