package services

// Backup Mode runtime (t-paliad-246 / m/paliad#77 Slice A).
//
// One file because all four pieces are tightly coupled:
//
//   - ArtifactStore interface + LocalDiskStore implementation
//     (storage abstraction; m picked local disk for v1, the interface
//     stays so a future swap to Supabase Storage is one impl away).
//
//   - BackupRunner — the orchestration the on-demand handler and the
//     (Slice B) scheduler share. Wraps the export pipeline:
//        1. INSERT paliad.backups (status='running')
//        2. INSERT paliad.system_audit_log (event_type='backup_created')
//        3. ExportService.WriteOrg → in-memory buffer
//        4. ArtifactStore.Put → file
//        5. UPDATE paliad.backups (status='done', storage_uri, …)
//        6. PATCH paliad.system_audit_log metadata
//
// Design: docs/design-backup-mode-2026-05-25.md.

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/jmoiron/sqlx"
)

// ---------------------------------------------------------------------------
// ArtifactStore interface + LocalDiskStore impl
// ---------------------------------------------------------------------------

// ArtifactStore persists the bytes of a backup artifact. The interface
// is deliberately small so Slice B can drop in a SupabaseStorageStore
// (or any object-store implementation) without changing the runner.
//
// URIs returned by Put are opaque to callers — they round-trip through
// Get/Delete. v1's LocalDiskStore uses `file://<absolute-path>`.
type ArtifactStore interface {
	// Put writes the given body to the store under the given key and
	// returns the URI for later retrieval. Implementations must overwrite
	// an existing object at the same key (catalog rows make keys unique
	// in practice, but the contract is overwrite-on-conflict to keep
	// retries idempotent).
	Put(ctx context.Context, key string, body []byte) (uri string, err error)
	// Get streams the artifact bytes at the given URI.
	Get(ctx context.Context, uri string) (rc io.ReadCloser, size int64, err error)
	// Delete removes the artifact at the given URI. Returns nil if the
	// artifact is already absent (idempotent).
	Delete(ctx context.Context, uri string) error
}

// LocalDiskStore is the v1 ArtifactStore — writes artifacts to a local
// directory specified at construction time. Mode 0700 on the directory
// + 0600 on artifact files keeps the files private to the paliad
// process owner on the Dokploy host.
type LocalDiskStore struct {
	dir string
}

// NewLocalDiskStore creates a LocalDiskStore rooted at dir. Creates the
// directory (0700) if it doesn't exist. Returns an error if dir is
// empty or the mkdir fails.
func NewLocalDiskStore(dir string) (*LocalDiskStore, error) {
	if strings.TrimSpace(dir) == "" {
		return nil, errors.New("LocalDiskStore: empty directory")
	}
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return nil, fmt.Errorf("LocalDiskStore mkdir %q: %w", dir, err)
	}
	abs, err := filepath.Abs(dir)
	if err != nil {
		return nil, fmt.Errorf("LocalDiskStore abs %q: %w", dir, err)
	}
	return &LocalDiskStore{dir: abs}, nil
}

// Put writes body to <dir>/<key>. Returns a file:// URI.
func (s *LocalDiskStore) Put(_ context.Context, key string, body []byte) (string, error) {
	if err := validateKey(key); err != nil {
		return "", err
	}
	full := filepath.Join(s.dir, key)
	if err := os.WriteFile(full, body, 0o600); err != nil {
		return "", fmt.Errorf("LocalDiskStore write %q: %w", full, err)
	}
	return "file://" + full, nil
}

// Get opens the file referenced by uri. Returns a *os.File (io.ReadCloser)
// + the file's size in bytes.
func (s *LocalDiskStore) Get(_ context.Context, uri string) (io.ReadCloser, int64, error) {
	path, err := s.pathFromURI(uri)
	if err != nil {
		return nil, 0, err
	}
	info, err := os.Stat(path)
	if err != nil {
		return nil, 0, fmt.Errorf("LocalDiskStore stat %q: %w", path, err)
	}
	f, err := os.Open(path)
	if err != nil {
		return nil, 0, fmt.Errorf("LocalDiskStore open %q: %w", path, err)
	}
	return f, info.Size(), nil
}

// Delete removes the file referenced by uri. Idempotent — missing file
// is treated as success.
func (s *LocalDiskStore) Delete(_ context.Context, uri string) error {
	path, err := s.pathFromURI(uri)
	if err != nil {
		return err
	}
	if err := os.Remove(path); err != nil && !errors.Is(err, os.ErrNotExist) {
		return fmt.Errorf("LocalDiskStore remove %q: %w", path, err)
	}
	return nil
}

// pathFromURI parses a file:// URI and validates that the resolved
// path is inside this store's directory. Defense-in-depth against a
// malformed catalog row pointing at an arbitrary file.
func (s *LocalDiskStore) pathFromURI(uri string) (string, error) {
	u, err := url.Parse(uri)
	if err != nil {
		return "", fmt.Errorf("LocalDiskStore parse uri %q: %w", uri, err)
	}
	if u.Scheme != "file" {
		return "", fmt.Errorf("LocalDiskStore: unsupported uri scheme %q (want file://)", u.Scheme)
	}
	// url.Parse drops the leading "/" for file:// URIs into u.Path.
	path := u.Path
	if u.Host != "" {
		// "file://host/path" — we don't issue these. Reject.
		return "", fmt.Errorf("LocalDiskStore: file:// uri with host is unsupported (%q)", uri)
	}
	clean := filepath.Clean(path)
	rel, err := filepath.Rel(s.dir, clean)
	if err != nil || strings.HasPrefix(rel, "..") {
		return "", fmt.Errorf("LocalDiskStore: uri %q resolves outside store dir %q", uri, s.dir)
	}
	return clean, nil
}

// validateKey rejects keys that would escape the store dir (path
// separators, "..", absolute paths). Backup runner uses
// "<uuid>.zip" so this is a defensive guard.
func validateKey(key string) error {
	if key == "" {
		return errors.New("ArtifactStore: empty key")
	}
	if strings.ContainsAny(key, "/\\") {
		return fmt.Errorf("ArtifactStore: key %q contains path separator", key)
	}
	if strings.Contains(key, "..") {
		return fmt.Errorf("ArtifactStore: key %q contains traversal", key)
	}
	if filepath.IsAbs(key) {
		return fmt.Errorf("ArtifactStore: key %q is absolute", key)
	}
	return nil
}

// ---------------------------------------------------------------------------
// BackupRunner
// ---------------------------------------------------------------------------

// BackupKind discriminates a scheduled run from an on-demand one.
const (
	BackupKindOnDemand  = "on_demand"
	BackupKindScheduled = "scheduled"
)

// BackupStatus values mirror the paliad.backups status check constraint.
const (
	BackupStatusRunning = "running"
	BackupStatusDone    = "done"
	BackupStatusFailed  = "failed"
)

// SystemActorEmail is the sentinel actor_email written for scheduled
// backups (kind='scheduled'). Matches design §3.4 — we don't seed a
// phantom user, we just stamp the audit row with a stable sentinel.
const SystemActorEmail = "system@paliad"

// BackupActor identifies who requested a backup. For kind='scheduled'
// pass (nil, SystemActorEmail, "Paliad Backup System"). For on-demand
// pass the calling admin's id/email/display_name.
type BackupActor struct {
	ID    *uuid.UUID
	Email string
	Label string
}

// BackupResult is what Run returns to the caller. Empty on failure
// (the error gets the failure detail; the catalog/audit rows are
// already updated).
type BackupResult struct {
	ID         uuid.UUID
	AuditID    uuid.UUID
	StorageURI string
	SizeBytes  int64
	RowCounts  map[string]int
	SheetCount int
}

// BackupRunner orchestrates one backup run. Stateless except for the
// wired dependencies; safe to share across goroutines (the handler
// holds one instance; the Slice B scheduler will hold the same one).
type BackupRunner struct {
	db     *sqlx.DB
	export *ExportService
	store  ArtifactStore
}

// NewBackupRunner wires the runner. All three deps are required; the
// caller (cmd/server/main.go) is responsible for instantiating the
// ArtifactStore from env config.
func NewBackupRunner(db *sqlx.DB, export *ExportService, store ArtifactStore) *BackupRunner {
	return &BackupRunner{db: db, export: export, store: store}
}

// Store returns the configured store. Exposed for the download handler
// to stream artifacts via Get.
func (r *BackupRunner) Store() ArtifactStore { return r.store }

// Run performs one backup. Writes catalog + audit rows, generates the
// bundle via ExportService.WriteOrg, uploads to the configured store,
// patches catalog + audit on success/failure.
//
// On any error after the catalog/audit rows are written, the rows are
// patched to status='failed' / event_type='backup_failed' before
// returning. The returned error is always the export/upload failure —
// catalog-update failures during the failure-recovery path are best-
// effort logged but not surfaced (the real error is the one to bubble).
func (r *BackupRunner) Run(ctx context.Context, kind string, actor BackupActor) (BackupResult, error) {
	if kind != BackupKindOnDemand && kind != BackupKindScheduled {
		return BackupResult{}, fmt.Errorf("BackupRunner.Run: invalid kind %q", kind)
	}
	if actor.Email == "" {
		return BackupResult{}, errors.New("BackupRunner.Run: empty actor email")
	}

	now := time.Now().UTC()
	spec := ExportSpec{
		Scope:       ExportScopeOrg,
		ActorID:     uuid.Nil, // overwritten below when actor.ID != nil
		ActorEmail:  actor.Email,
		ActorLabel:  actor.Label,
		GeneratedAt: now,
	}
	if actor.ID != nil {
		spec.ActorID = *actor.ID
	}

	// Step 1+2: catalog row (status='running') + audit row
	// (event_type='backup_created'). Both happen before the export
	// generation so failure paths can always find them.
	catalogID, err := r.insertCatalogRow(ctx, kind, actor, uuid.Nil, now)
	if err != nil {
		return BackupResult{}, fmt.Errorf("backup catalog insert: %w", err)
	}
	auditID, err := r.insertAuditRow(ctx, kind, actor, catalogID, now)
	if err != nil {
		// Best-effort patch on the catalog row so it doesn't sit
		// "running" forever.
		r.patchCatalogRowFailed(context.Background(), catalogID, fmt.Errorf("audit insert: %w", err))
		return BackupResult{}, fmt.Errorf("backup audit insert: %w", err)
	}
	// Back-link the audit id into the catalog row so the UI can JOIN.
	if err := r.linkAuditID(ctx, catalogID, auditID); err != nil {
		// Non-fatal — the link is for UI convenience, not correctness.
		// The error is logged via the patch path; we keep going.
	}

	// Step 3: generate the bundle into an in-memory buffer. We materialise
	// fully before uploading so a partial upload doesn't strand bytes in
	// the store under a "done" catalog row.
	var buf bytes.Buffer
	meta, err := r.export.WriteOrg(ctx, &buf, spec)
	if err != nil {
		r.failRun(context.Background(), catalogID, auditID, fmt.Errorf("generate: %w", err))
		return BackupResult{}, fmt.Errorf("backup generate: %w", err)
	}

	// Step 4: upload to storage. Key = "<catalog_id>.zip".
	key := catalogID.String() + ".zip"
	uri, err := r.store.Put(ctx, key, buf.Bytes())
	if err != nil {
		r.failRun(context.Background(), catalogID, auditID, fmt.Errorf("upload: %w", err))
		return BackupResult{}, fmt.Errorf("backup upload: %w", err)
	}

	// Step 5+6: patch catalog + audit on success.
	size := int64(buf.Len())
	sheetCount := len(meta.RowCounts)
	if err := r.patchCatalogRowDone(ctx, catalogID, uri, size, sheetCount, meta); err != nil {
		// At this point the artifact is on disk, the audit row was
		// inserted, and the only thing that failed is the catalog
		// flip. Surface as an error so the handler can log; the
		// artifact is recoverable manually via the audit metadata.
		return BackupResult{}, fmt.Errorf("backup catalog patch: %w", err)
	}
	if err := r.patchAuditRowDone(ctx, auditID, uri, size, sheetCount, meta); err != nil {
		// Non-fatal — the catalog row is already authoritative; the
		// audit row is the audit-trail twin. Log via the caller.
	}

	return BackupResult{
		ID:         catalogID,
		AuditID:    auditID,
		StorageURI: uri,
		SizeBytes:  size,
		RowCounts:  meta.RowCounts,
		SheetCount: sheetCount,
	}, nil
}

// RecordDownload writes a paliad.system_audit_log row of
// event_type='backup_downloaded' when an admin downloads a backup
// via /api/admin/backups/{id}/file. Separate row per click — the
// existing 'backup_created' row stays untouched.
func (r *BackupRunner) RecordDownload(ctx context.Context, backupID uuid.UUID, by BackupActor) error {
	if by.Email == "" {
		return errors.New("BackupRunner.RecordDownload: empty actor email")
	}
	meta, _ := json.Marshal(map[string]any{
		"backup_id":            backupID.String(),
		"downloaded_by_email":  by.Email,
		"downloaded_at":        time.Now().UTC().Format(time.RFC3339),
	})
	var actorID any
	if by.ID != nil {
		actorID = *by.ID
	}
	_, err := r.db.ExecContext(ctx,
		`INSERT INTO paliad.system_audit_log
		      (event_type, actor_id, actor_email, scope, scope_root, metadata)
		 VALUES ('backup_downloaded', $1, $2, 'org', NULL, $3::jsonb)`,
		actorID, by.Email, string(meta),
	)
	if err != nil {
		return fmt.Errorf("backup_downloaded audit insert: %w", err)
	}
	return nil
}

// ---------------------------------------------------------------------------
// Catalog read helpers (List + Get for the admin UI)
// ---------------------------------------------------------------------------

// BackupSummary is the row shape returned by ListBackups + GetBackup —
// shaped for the /admin/backups UI. Nullable columns are pointers.
type BackupSummary struct {
	ID                uuid.UUID  `db:"id" json:"id"`
	Kind              string     `db:"kind" json:"kind"`
	Status            string     `db:"status" json:"status"`
	RequestedBy       *uuid.UUID `db:"requested_by" json:"requested_by,omitempty"`
	RequestedByEmail  string     `db:"requested_by_email" json:"requested_by_email"`
	AuditID           *uuid.UUID `db:"audit_id" json:"audit_id,omitempty"`
	StorageURI        *string    `db:"storage_uri" json:"storage_uri,omitempty"`
	SizeBytes         *int64     `db:"size_bytes" json:"size_bytes,omitempty"`
	RowCounts         []byte     `db:"row_counts" json:"row_counts,omitempty"`
	SheetCount        *int       `db:"sheet_count" json:"sheet_count,omitempty"`
	Warnings          []byte     `db:"warnings" json:"warnings,omitempty"`
	Error             *string    `db:"error" json:"error,omitempty"`
	StartedAt         time.Time  `db:"started_at" json:"started_at"`
	FinishedAt        *time.Time `db:"finished_at" json:"finished_at,omitempty"`
	DeletedAt         *time.Time `db:"deleted_at" json:"deleted_at,omitempty"`
}

// ListBackups returns the most recent backups (highest started_at first),
// capped at limit. limit <= 0 means default (100).
func (r *BackupRunner) ListBackups(ctx context.Context, limit int) ([]BackupSummary, error) {
	if limit <= 0 {
		limit = 100
	}
	var rows []BackupSummary
	err := r.db.SelectContext(ctx, &rows,
		`SELECT id, kind, status, requested_by, requested_by_email, audit_id,
		         storage_uri, size_bytes, row_counts, sheet_count, warnings,
		         error, started_at, finished_at, deleted_at
		    FROM paliad.backups
		ORDER BY started_at DESC
		   LIMIT $1`,
		limit,
	)
	if err != nil {
		return nil, fmt.Errorf("list backups: %w", err)
	}
	return rows, nil
}

// GetBackup fetches one backup by id. Returns sql.ErrNoRows when not
// found (caller maps to 404).
func (r *BackupRunner) GetBackup(ctx context.Context, id uuid.UUID) (BackupSummary, error) {
	var row BackupSummary
	err := r.db.GetContext(ctx, &row,
		`SELECT id, kind, status, requested_by, requested_by_email, audit_id,
		         storage_uri, size_bytes, row_counts, sheet_count, warnings,
		         error, started_at, finished_at, deleted_at
		    FROM paliad.backups
		   WHERE id = $1`,
		id,
	)
	if err != nil {
		return BackupSummary{}, err
	}
	return row, nil
}

// ---------------------------------------------------------------------------
// Catalog + audit SQL helpers (private — used by Run + RecordDownload).
// ---------------------------------------------------------------------------

func (r *BackupRunner) insertCatalogRow(ctx context.Context, kind string, actor BackupActor, auditID uuid.UUID, now time.Time) (uuid.UUID, error) {
	var actorID any
	if actor.ID != nil {
		actorID = *actor.ID
	}
	var auditArg any
	if auditID != uuid.Nil {
		auditArg = auditID
	}
	var id uuid.UUID
	err := r.db.QueryRowxContext(ctx,
		`INSERT INTO paliad.backups
		      (kind, status, requested_by, requested_by_email, audit_id, started_at)
		 VALUES ($1, 'running', $2, $3, $4, $5)
		 RETURNING id`,
		kind, actorID, actor.Email, auditArg, now,
	).Scan(&id)
	if err != nil {
		return uuid.Nil, err
	}
	return id, nil
}

func (r *BackupRunner) insertAuditRow(ctx context.Context, kind string, actor BackupActor, catalogID uuid.UUID, now time.Time) (uuid.UUID, error) {
	meta, _ := json.Marshal(map[string]any{
		"kind":                  kind,
		"catalog_id":            catalogID.String(),
		"requested_by_email":    actor.Email,
		"requested_at":          now.Format(time.RFC3339),
	})
	var actorID any
	if actor.ID != nil {
		actorID = *actor.ID
	}
	var id uuid.UUID
	err := r.db.QueryRowxContext(ctx,
		`INSERT INTO paliad.system_audit_log
		      (event_type, actor_id, actor_email, scope, scope_root, metadata)
		 VALUES ('backup_created', $1, $2, 'org', NULL, $3::jsonb)
		 RETURNING id`,
		actorID, actor.Email, string(meta),
	).Scan(&id)
	if err != nil {
		return uuid.Nil, err
	}
	return id, nil
}

func (r *BackupRunner) linkAuditID(ctx context.Context, catalogID, auditID uuid.UUID) error {
	_, err := r.db.ExecContext(ctx,
		`UPDATE paliad.backups SET audit_id = $2 WHERE id = $1`,
		catalogID, auditID,
	)
	return err
}

func (r *BackupRunner) patchCatalogRowDone(ctx context.Context, id uuid.UUID, uri string, size int64, sheetCount int, meta ExportMeta) error {
	rcJSON, _ := json.Marshal(meta.RowCounts)
	warnJSON, _ := json.Marshal(meta.Warnings)
	if meta.Warnings == nil {
		warnJSON = []byte("[]")
	}
	_, err := r.db.ExecContext(ctx,
		`UPDATE paliad.backups
		    SET status      = 'done',
		        storage_uri = $2,
		        size_bytes  = $3,
		        sheet_count = $4,
		        row_counts  = $5::jsonb,
		        warnings    = $6::jsonb,
		        finished_at = now()
		  WHERE id = $1`,
		id, uri, size, sheetCount, string(rcJSON), string(warnJSON),
	)
	return err
}

func (r *BackupRunner) patchCatalogRowFailed(ctx context.Context, id uuid.UUID, runErr error) {
	_, _ = r.db.ExecContext(ctx,
		`UPDATE paliad.backups
		    SET status      = 'failed',
		        error       = $2,
		        finished_at = now()
		  WHERE id = $1`,
		id, runErr.Error(),
	)
}

func (r *BackupRunner) patchAuditRowDone(ctx context.Context, id uuid.UUID, uri string, size int64, sheetCount int, meta ExportMeta) error {
	payload, _ := json.Marshal(map[string]any{
		"row_counts":      meta.RowCounts,
		"file_size_bytes": size,
		"sheet_count":     sheetCount,
		"storage_uri":     uri,
		"warnings":        meta.Warnings,
		"completed_at":    time.Now().UTC().Format(time.RFC3339),
	})
	_, err := r.db.ExecContext(ctx,
		`UPDATE paliad.system_audit_log
		    SET metadata = metadata || $2::jsonb,
		        updated_at = now()
		  WHERE id = $1`,
		id, string(payload),
	)
	return err
}

func (r *BackupRunner) patchAuditRowFailed(ctx context.Context, id uuid.UUID, runErr error) {
	payload, _ := json.Marshal(map[string]any{
		"error":     runErr.Error(),
		"failed_at": time.Now().UTC().Format(time.RFC3339),
	})
	_, _ = r.db.ExecContext(ctx,
		`UPDATE paliad.system_audit_log
		    SET event_type = 'backup_failed',
		        metadata = metadata || $2::jsonb,
		        updated_at = now()
		  WHERE id = $1`,
		id, string(payload),
	)
}

// failRun is the shared failure-recovery path: patch the catalog +
// audit rows to their failed states. Uses a context.Background so the
// patch happens even if the original ctx is already cancelled.
func (r *BackupRunner) failRun(ctx context.Context, catalogID, auditID uuid.UUID, runErr error) {
	r.patchCatalogRowFailed(ctx, catalogID, runErr)
	r.patchAuditRowFailed(ctx, auditID, runErr)
}