package dataexport

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"data-terminal-cloud/internal/audit"
	"data-terminal-cloud/internal/database"
	"data-terminal-cloud/internal/outbox"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

type objectStore interface {
	PutJSON(context.Context, string, []byte, string) (int64, error)
	Remove(context.Context, string) error
}

type Processor struct {
	pool      *pgxpool.Pool
	store     objectStore
	audit     *audit.Repository
	objectTTL time.Duration
}

func NewProcessor(pool *pgxpool.Pool, store objectStore, objectTTL time.Duration) (*Processor, error) {
	if pool == nil || store == nil || objectTTL <= 0 {
		return nil, errors.New("database, object store and positive object TTL are required")
	}
	return &Processor{pool: pool, store: store, audit: audit.NewRepository(), objectTTL: objectTTL}, nil
}

func (p *Processor) Handle(ctx context.Context, event outbox.Event) error {
	if err := p.process(ctx, event.AggregateID); err != nil {
		_, _ = p.pool.Exec(ctx, `UPDATE export_task SET status='FAILED',last_error='export generation failed',updated_at=now() WHERE id=$1::uuid AND status<>'EXPIRED'`, event.AggregateID)
		return err
	}
	return nil
}

func (p *Processor) process(ctx context.Context, taskID string) error {
	var tenantID, tenantPublicID, subjectID, subjectPublicID, taskPublicID, status, subjectStatus string
	var scopeJSON []byte
	found := false
	err := database.Transact(ctx, p.pool, func(tx pgx.Tx) error {
		if err := tx.QueryRow(ctx, `SELECT et.tenant_id::text,t.public_id::text,et.subject_id::text,sp.public_id::text,et.public_id::text,et.status,sp.status,et.scope FROM export_task et JOIN tenant t ON t.id=et.tenant_id JOIN subject_profile sp ON sp.id=et.subject_id WHERE et.id=$1::uuid FOR UPDATE OF et`, taskID).Scan(&tenantID, &tenantPublicID, &subjectID, &subjectPublicID, &taskPublicID, &status, &subjectStatus, &scopeJSON); errors.Is(err, pgx.ErrNoRows) {
			return nil
		} else if err != nil {
			return err
		}
		found = true
		if status == "READY" || status == "EXPIRED" {
			return nil
		}
		if subjectStatus != "active" && subjectStatus != "suspended" {
			_, err := tx.Exec(ctx, `UPDATE export_task SET status='EXPIRED',scope='{}'::jsonb,object_ref=NULL,object_size=NULL,content_digest=NULL,expires_at=NULL,last_error=NULL,updated_at=now() WHERE id=$1::uuid`, taskID)
			status = "EXPIRED"
			return err
		}
		_, err := tx.Exec(ctx, `UPDATE export_task SET status='RUNNING',attempts=attempts+1,last_error=NULL,updated_at=now() WHERE id=$1::uuid`, taskID)
		return err
	})
	if err != nil || !found || status == "READY" || status == "EXPIRED" {
		return err
	}

	categories, err := categoriesFromScope(scopeJSON)
	if err != nil {
		return err
	}
	data := make(map[string]json.RawMessage, len(categories))
	for _, category := range categories {
		value, err := p.collectCategory(ctx, category, tenantID, subjectID)
		if err != nil {
			return fmt.Errorf("collect export category %s: %w", category, err)
		}
		data[category] = value
	}
	document := struct {
		SchemaVersion string                     `json:"schema_version"`
		GeneratedAt   time.Time                  `json:"generated_at"`
		SubjectID     string                     `json:"subject_id"`
		Scope         []string                   `json:"scope"`
		Data          map[string]json.RawMessage `json:"data"`
	}{"subject-export-v1", time.Now().UTC(), subjectPublicID, categories, data}
	content, err := json.MarshalIndent(document, "", "  ")
	if err != nil {
		return err
	}
	digestValue := sha256.Sum256(content)
	digest := hex.EncodeToString(digestValue[:])
	tenantDigest := sha256.Sum256([]byte(tenantID))
	objectRef := fmt.Sprintf("tenants/%s/exports/%s/v1.json", hex.EncodeToString(tenantDigest[:16]), taskPublicID)
	size, err := p.store.PutJSON(ctx, objectRef, content, digest)
	if err != nil {
		return outbox.Retryable(err)
	}
	expiresAt := time.Now().UTC().Add(p.objectTTL)
	finalizeErr := database.Transact(ctx, p.pool, func(tx pgx.Tx) error {
		var currentSubjectStatus string
		if err := tx.QueryRow(ctx, `SELECT status FROM subject_profile WHERE tenant_id=$1::uuid AND id=$2::uuid FOR SHARE`, tenantID, subjectID).Scan(&currentSubjectStatus); err != nil {
			return err
		}
		if currentSubjectStatus != "active" && currentSubjectStatus != "suspended" {
			_, err := tx.Exec(ctx, `UPDATE export_task SET status='EXPIRED',scope='{}'::jsonb,object_ref=NULL,object_size=NULL,content_digest=NULL,expires_at=NULL,last_error=NULL,updated_at=now() WHERE id=$1::uuid`, taskID)
			return err
		}
		tag, err := tx.Exec(ctx, `UPDATE export_task SET status='READY',object_ref=$2,object_size=$3,content_digest=$4,expires_at=$5,completed_at=now(),last_error=NULL,updated_at=now() WHERE id=$1::uuid AND status IN ('RUNNING','FAILED')`, taskID, objectRef, size, digest, expiresAt)
		if err != nil {
			return err
		}
		if tag.RowsAffected() != 1 {
			return errors.New("export task state changed before completion")
		}
		return p.audit.Record(ctx, tx, audit.Event{TenantID: &tenantID, ActorType: "system", Action: "export.ready", ResourceType: "export_task", ResourceID: &taskPublicID, Result: "success", Detail: map[string]any{"tenant_public_id": tenantPublicID, "object_size": size, "content_digest": digest, "expires_at": expiresAt}})
	})
	if finalizeErr != nil {
		_ = p.store.Remove(ctx, objectRef)
		return finalizeErr
	}
	var finalStatus string
	if err := p.pool.QueryRow(ctx, `SELECT status FROM export_task WHERE id=$1::uuid`, taskID).Scan(&finalStatus); err != nil {
		_ = p.store.Remove(ctx, objectRef)
		return err
	}
	if finalStatus != "READY" {
		return p.store.Remove(ctx, objectRef)
	}
	return nil
}

func categoriesFromScope(scopeJSON []byte) ([]string, error) {
	var scope struct {
		Categories []string `json:"categories"`
	}
	if err := json.Unmarshal(scopeJSON, &scope); err != nil {
		return nil, err
	}
	if len(scope.Categories) == 0 {
		return []string{"profile", "consents", "device_bindings", "conversations", "transcripts", "summaries", "stories", "memories"}, nil
	}
	return scope.Categories, nil
}

func (p *Processor) collectCategory(ctx context.Context, category, tenantID, subjectID string) (json.RawMessage, error) {
	queries := map[string]string{
		"profile":         `SELECT jsonb_build_object('id',public_id,'preferred_name',preferred_name,'language',language,'timezone',timezone,'profile_data',profile_data,'conversation_preferences',conversation_preferences,'status',status,'version',profile_version,'created_at',created_at,'updated_at',updated_at) FROM subject_profile WHERE tenant_id=$1::uuid AND id=$2::uuid`,
		"consents":        `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',public_id,'type',consent_type,'scope',scope,'policy_version',policy_version,'notice_digest',notice_digest,'granted_at',granted_at,'expires_at',expires_at,'withdrawn_at',withdrawn_at,'version',version) ORDER BY granted_at,id),'[]'::jsonb) FROM consent_record WHERE tenant_id=$1::uuid AND subject_id=$2::uuid`,
		"device_bindings": `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',db.public_id,'device_id',d.public_id,'model',d.model,'bound_at',db.bound_at,'unbound_at',db.unbound_at,'reason',db.reason) ORDER BY db.bound_at,db.id),'[]'::jsonb) FROM device_binding db JOIN device d ON d.id=db.device_id AND d.tenant_id=db.tenant_id WHERE db.tenant_id=$1::uuid AND db.subject_id=$2::uuid`,
		"conversations":   `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',public_id,'engine_mode',engine_mode,'retention_mode',retention_mode,'status',status,'started_at',started_at,'ended_at',ended_at,'stop_reason',stop_reason,'failure_code',failure_code,'created_at',created_at) ORDER BY created_at,id),'[]'::jsonb) FROM conversation WHERE tenant_id=$1::uuid AND subject_id=$2::uuid`,
		"transcripts":     `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',public_id,'conversation_id',(SELECT public_id FROM conversation WHERE id=conversation_turn.conversation_id),'sequence_no',sequence_no,'speaker',speaker,'start_at',start_at,'end_at',end_at,'final_text',final_text,'interrupted',interrupted,'source_type',source_type) ORDER BY start_at,id),'[]'::jsonb) FROM conversation_turn WHERE tenant_id=$1::uuid AND subject_id=$2::uuid`,
		"summaries":       `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',public_id,'conversation_id',(SELECT public_id FROM conversation WHERE id=conversation_summary.conversation_id),'type',summary_type,'content',content,'source_turn_ids',source_turn_ids,'generation_version',generation_version,'status',status,'created_at',created_at) ORDER BY created_at,id),'[]'::jsonb) FROM conversation_summary WHERE tenant_id=$1::uuid AND subject_id=$2::uuid`,
		"stories":         `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',sd.public_id,'conversation_id',c.public_id,'title',sd.title,'status',sd.status,'sensitivity',sd.sensitivity,'version',sd.version,'content',sr.content,'revision_no',sr.revision_no,'sources',(SELECT COALESCE(jsonb_agg(jsonb_build_object('turn_id',ct.public_id,'sequence_no',ct.sequence_no,'speaker',ss.source_role,'text',ct.final_text) ORDER BY ct.sequence_no),'[]'::jsonb) FROM story_source ss JOIN conversation_turn ct ON ct.id=ss.conversation_turn_id WHERE ss.story_revision_id=sr.id),'facts',(SELECT COALESCE(jsonb_agg(jsonb_build_object('id',fc.public_id,'type',fc.fact_type,'content',fc.content,'basis',fc.statement_basis,'status',fc.status,'source_turn_ids',fc.source_turn_ids) ORDER BY fc.created_at,fc.id),'[]'::jsonb) FROM fact_candidate fc WHERE fc.story_id=sd.id)) ORDER BY sd.created_at,sd.id),'[]'::jsonb) FROM story_draft sd JOIN conversation c ON c.id=sd.conversation_id LEFT JOIN story_revision sr ON sr.id=sd.current_revision_id WHERE sd.tenant_id=$1::uuid AND sd.subject_id=$2::uuid`,
		"memories":        `SELECT COALESCE(jsonb_agg(jsonb_build_object('id',cm.public_id,'status',cm.status,'sensitivity',cm.sensitivity,'valid_from',cm.valid_from,'valid_to',cm.valid_to,'version',cm.version,'memory_version',mv.version_no,'content',mv.content,'source_refs',mv.source_refs,'confirmed_at',mv.confirmed_at,'change_reason',mv.change_reason) ORDER BY cm.created_at,cm.id),'[]'::jsonb) FROM curated_memory cm LEFT JOIN memory_version mv ON mv.id=cm.current_version_id WHERE cm.tenant_id=$1::uuid AND cm.subject_id=$2::uuid AND cm.status<>'DELETED'`,
	}
	query, ok := queries[category]
	if !ok {
		return nil, fmt.Errorf("unsupported category %q", category)
	}
	var value []byte
	if err := p.pool.QueryRow(ctx, query, tenantID, subjectID).Scan(&value); err != nil {
		return nil, err
	}
	return json.RawMessage(value), nil
}

type ExpiryScanner struct {
	pool     *pgxpool.Pool
	store    objectStore
	logger   *slog.Logger
	interval time.Duration
}

func NewExpiryScanner(pool *pgxpool.Pool, store objectStore, logger *slog.Logger, interval time.Duration) (*ExpiryScanner, error) {
	if pool == nil || store == nil || logger == nil || interval <= 0 {
		return nil, errors.New("database, object store, logger and interval are required")
	}
	return &ExpiryScanner{pool: pool, store: store, logger: logger, interval: interval}, nil
}

func (s *ExpiryScanner) Run(ctx context.Context) {
	ticker := time.NewTicker(s.interval)
	defer ticker.Stop()
	for {
		s.scan(ctx)
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
		}
	}
}

func (s *ExpiryScanner) scan(ctx context.Context) {
	rows, err := s.pool.Query(ctx, `SELECT id::text,tenant_id::text,public_id::text,object_ref FROM export_task WHERE status='READY' AND expires_at<=now() ORDER BY expires_at LIMIT 50`)
	if err != nil {
		s.logger.Error("scan expired exports failed", "error", err)
		return
	}
	type item struct{ id, tenantID, publicID, objectRef string }
	items := []item{}
	for rows.Next() {
		var value item
		if err := rows.Scan(&value.id, &value.tenantID, &value.publicID, &value.objectRef); err != nil {
			rows.Close()
			s.logger.Error("scan expired export row failed", "error", err)
			return
		}
		items = append(items, value)
	}
	rows.Close()
	for _, value := range items {
		if err := s.store.Remove(ctx, value.objectRef); err != nil {
			s.logger.Warn("remove expired export failed", "export_id", value.publicID, "error", err)
			continue
		}
		err := database.Transact(ctx, s.pool, func(tx pgx.Tx) error {
			tag, err := tx.Exec(ctx, `UPDATE export_task SET status='EXPIRED',object_ref=NULL,updated_at=now() WHERE id=$1::uuid AND status='READY' AND expires_at<=now()`, value.id)
			if err != nil || tag.RowsAffected() != 1 {
				return err
			}
			return audit.NewRepository().Record(ctx, tx, audit.Event{TenantID: &value.tenantID, ActorType: "system", Action: "export.expire", ResourceType: "export_task", ResourceID: &value.publicID, Result: "success"})
		})
		if err != nil {
			s.logger.Error("mark export expired failed", "export_id", value.publicID, "error", err)
		}
	}
}

func sanitizeError(value string) string {
	value = strings.TrimSpace(value)
	if len(value) > 500 {
		return value[:500]
	}
	return value
}