package s3tables

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"strings"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
)

const (
	TablesPath       = s3_constants.DefaultBucketsPath
	DefaultAccountID = "000000000000"
	DefaultRegion    = "us-east-1"

	// Extended entry attributes for metadata storage
	ExtendedKeyTableBucket = "s3tables.tableBucket"
	ExtendedKeyMetadata    = "s3tables.metadata"
	ExtendedKeyPolicy      = "s3tables.policy"
	ExtendedKeyTags        = "s3tables.tags"

	// Maximum request body size (10MB)
	maxRequestBodySize = 10 * 1024 * 1024
)

var (
	ErrVersionTokenMismatch = errors.New("version token mismatch")
	ErrAccessDenied         = errors.New("access denied")
)

type ResourceType string

const (
	ResourceTypeBucket ResourceType = "bucket"
	ResourceTypeTable  ResourceType = "table"
)

// S3TablesHandler handles S3 Tables API requests
type S3TablesHandler struct {
	region        string
	accountID     string
	defaultAllow  bool // Whether to allow access by default (for zero-config IAM)
	iamAuthorizer IAMAuthorizer
}

// NewS3TablesHandler creates a new S3 Tables handler
func NewS3TablesHandler() *S3TablesHandler {
	return &S3TablesHandler{
		region:       DefaultRegion,
		accountID:    DefaultAccountID,
		defaultAllow: false,
	}
}

// SetRegion sets the AWS region for ARN generation
func (h *S3TablesHandler) SetRegion(region string) {
	if region != "" {
		h.region = region
	}
}

// SetAccountID sets the AWS account ID for ARN generation
func (h *S3TablesHandler) SetAccountID(accountID string) {
	if accountID != "" {
		h.accountID = accountID
	}
}

// SetDefaultAllow sets whether to allow access by default
func (h *S3TablesHandler) SetDefaultAllow(allow bool) {
	h.defaultAllow = allow
}

// FilerClient interface for filer operations
type FilerClient interface {
	WithFilerClient(streamingMode bool, fn func(client filer_pb.SeaweedFilerClient) error) error
}

// HandleRequest is the main entry point for S3 Tables API requests
func (h *S3TablesHandler) HandleRequest(w http.ResponseWriter, r *http.Request, filerClient FilerClient) {
	operation := r.Header.Get("X-Amz-Target")
	if operation != "" {
		if idx := strings.LastIndex(operation, "."); idx != -1 {
			operation = operation[idx+1:]
		}
	}
	if operation == "" {
		glog.V(1).Infof("S3Tables: missing X-Amz-Target header")
		h.writeError(w, http.StatusBadRequest, ErrCodeInvalidRequest, "Missing X-Amz-Target header")
		return
	}

	glog.V(3).Infof("S3Tables: handling operation %s", operation)

	var err error
	switch operation {
	// Table Bucket operations
	case "CreateTableBucket":
		err = h.handleCreateTableBucket(w, r, filerClient)
	case "GetTableBucket":
		err = h.handleGetTableBucket(w, r, filerClient)
	case "ListTableBuckets":
		err = h.handleListTableBuckets(w, r, filerClient)
	case "DeleteTableBucket":
		err = h.handleDeleteTableBucket(w, r, filerClient)

	// Table Bucket Policy operations
	case "PutTableBucketPolicy":
		err = h.handlePutTableBucketPolicy(w, r, filerClient)
	case "GetTableBucketPolicy":
		err = h.handleGetTableBucketPolicy(w, r, filerClient)
	case "DeleteTableBucketPolicy":
		err = h.handleDeleteTableBucketPolicy(w, r, filerClient)

	// Namespace operations
	case "CreateNamespace":
		err = h.handleCreateNamespace(w, r, filerClient)
	case "GetNamespace":
		err = h.handleGetNamespace(w, r, filerClient)
	case "ListNamespaces":
		err = h.handleListNamespaces(w, r, filerClient)
	case "DeleteNamespace":
		err = h.handleDeleteNamespace(w, r, filerClient)

	// Table operations
	case "CreateTable":
		err = h.handleCreateTable(w, r, filerClient)
	case "GetTable":
		err = h.handleGetTable(w, r, filerClient)
	case "ListTables":
		err = h.handleListTables(w, r, filerClient)
	case "UpdateTable":
		err = h.handleUpdateTable(w, r, filerClient)
	case "DeleteTable":
		err = h.handleDeleteTable(w, r, filerClient)

	// Table Policy operations
	case "PutTablePolicy":
		err = h.handlePutTablePolicy(w, r, filerClient)
	case "GetTablePolicy":
		err = h.handleGetTablePolicy(w, r, filerClient)
	case "DeleteTablePolicy":
		err = h.handleDeleteTablePolicy(w, r, filerClient)

	// Tagging operations
	case "TagResource":
		err = h.handleTagResource(w, r, filerClient)
	case "ListTagsForResource":
		err = h.handleListTagsForResource(w, r, filerClient)
	case "UntagResource":
		err = h.handleUntagResource(w, r, filerClient)

	default:
		h.writeError(w, http.StatusBadRequest, ErrCodeInvalidRequest, fmt.Sprintf("Unknown operation: %s", operation))
		return
	}

	if err != nil {
		glog.Errorf("S3Tables: error handling %s: %v", operation, err)
	}
}

// Principal/authorization helpers

// getAccountID returns a stable caller identifier for ownership and permission checks.
// Reflection depends on the identity shape produced by JWT/STS auth (Account *struct{Id string},
// Claims map[string]interface{} containing string values for preferred_username/sub, and optional
// identity name/header values). Changing those fields without updating the reflection here will
// break the handler, so refactorers should replace this with a typed interface if needed.
func (h *S3TablesHandler) getAccountID(r *http.Request) string {
	identityRaw := s3_constants.GetIdentityFromContext(r)
	if identityRaw != nil {
		// Use reflection to access identity fields and avoid import cycles.
		val := reflect.ValueOf(identityRaw)
		if val.Kind() == reflect.Ptr {
			val = val.Elem()
		}
		if val.Kind() == reflect.Struct {
			// Prefer stable claims from JWT/STS identities. Only "sub" is guaranteed durable per OIDC;
			// preferred_username is ergonomic but can rotate and may orphan ownership data, while email
			// is explicitly excluded to avoid storing PII in metadata.
			claimsField := val.FieldByName("Claims")
			if claimsField.IsValid() && claimsField.Kind() == reflect.Map && !claimsField.IsNil() && claimsField.Type().Key().Kind() == reflect.String {
				for _, claimKey := range []string{"sub", "preferred_username"} {
					claimVal := claimsField.MapIndex(reflect.ValueOf(claimKey))
					if !claimVal.IsValid() {
						continue
					}
					if claimVal.Kind() == reflect.Interface && !claimVal.IsNil() {
						claimVal = claimVal.Elem()
					}
					if claimVal.Kind() == reflect.String {
						if principal := normalizePrincipalID(claimVal.String()); principal != "" {
							return principal
						}
					}
				}
			}

			accountField := val.FieldByName("Account")
			if accountField.IsValid() && !accountField.IsNil() {
				accountVal := accountField.Elem()
				if accountVal.Kind() == reflect.Struct {
					idField := accountVal.FieldByName("Id")
					if idField.IsValid() && idField.Kind() == reflect.String {
						if principal := normalizePrincipalID(idField.String()); principal != "" {
							return principal
						}
					}
				}
			}
		}
	}

	if identityName := s3_constants.GetIdentityNameFromContext(r); identityName != "" {
		if principal := normalizePrincipalID(identityName); principal != "" {
			return principal
		}
	}

	if accountID := r.Header.Get(s3_constants.AmzAccountId); accountID != "" {
		if principal := normalizePrincipalID(accountID); principal != "" {
			return principal
		}
	}
	return h.accountID
}

// normalizePrincipalID collapses ARN and identity strings to a key that is stable within a single account.
// WARNING: this assumes identity names are unique per account; distinct principals such as
// arn:aws:iam::111:user/alice and arn:aws:iam::222:user/alice will both normalize to "alice".
// If future work adds multi-account support, revisit this function to include the account ID or full ARN
// so ownership checks remain correct.
func normalizePrincipalID(id string) string {
	id = strings.TrimSpace(id)
	if id == "" {
		return ""
	}
	// If this is an ARN (common for assumed roles), use the trailing segment as a
	// stable-ish principal key instead of embedding the full ARN in ownership fields.
	if strings.HasPrefix(id, "arn:") {
		if idx := strings.LastIndex(id, "/"); idx >= 0 && idx+1 < len(id) {
			return strings.TrimSpace(id[idx+1:])
		}
		if idx := strings.LastIndex(id, ":"); idx >= 0 && idx+1 < len(id) {
			return strings.TrimSpace(id[idx+1:])
		}
		return strings.TrimSpace(id)
	}
	return id
}

// getIdentityActions extracts the action list from the identity object in the request context.
// Uses reflection to avoid import cycles with s3api package.
func getIdentityActions(r *http.Request) []string {
	identityRaw := s3_constants.GetIdentityFromContext(r)
	if identityRaw == nil {
		return nil
	}

	// Use reflection to access the Actions field to avoid import cycle
	val := reflect.ValueOf(identityRaw)
	if val.Kind() == reflect.Ptr {
		val = val.Elem()
	}
	if val.Kind() != reflect.Struct {
		return nil
	}

	actionsField := val.FieldByName("Actions")
	if !actionsField.IsValid() || actionsField.Kind() != reflect.Slice {
		return nil
	}

	// Convert actions to string slice
	actions := make([]string, actionsField.Len())
	for i := 0; i < actionsField.Len(); i++ {
		action := actionsField.Index(i)
		// Action is likely a custom type (e.g., type Action string)
		// Convert to string using String() or direct string conversion
		if action.Kind() == reflect.String {
			actions[i] = action.String()
		} else if action.CanInterface() {
			// Try to convert via fmt.Sprint
			actions[i] = fmt.Sprint(action.Interface())
		}
	}
	return actions
}

// Request/Response helpers

func (h *S3TablesHandler) readRequestBody(r *http.Request, v interface{}) error {
	defer r.Body.Close()

	// Limit request body size to prevent unbounded reads
	limitedReader := io.LimitReader(r.Body, maxRequestBodySize+1)
	body, err := io.ReadAll(limitedReader)
	if err != nil {
		return fmt.Errorf("failed to read request body: %w", err)
	}

	// Check if body exceeds size limit
	if len(body) > maxRequestBodySize {
		return fmt.Errorf("request body too large: exceeds maximum size of %d bytes", maxRequestBodySize)
	}

	if len(body) == 0 {
		return nil
	}

	if err := json.Unmarshal(body, v); err != nil {
		return fmt.Errorf("failed to decode request: %w", err)
	}

	return nil
}

// Response writing helpers

func (h *S3TablesHandler) writeJSON(w http.ResponseWriter, status int, data interface{}) {
	w.Header().Set("Content-Type", "application/x-amz-json-1.1")
	w.WriteHeader(status)
	if data != nil {
		if err := json.NewEncoder(w).Encode(data); err != nil {
			glog.Errorf("S3Tables: failed to encode response: %v", err)
		}
	}
}

func (h *S3TablesHandler) writeError(w http.ResponseWriter, status int, code, message string) {
	w.Header().Set("Content-Type", "application/x-amz-json-1.1")
	w.WriteHeader(status)
	errorResponse := map[string]interface{}{
		"__type":  code,
		"message": message,
	}
	if err := json.NewEncoder(w).Encode(errorResponse); err != nil {
		glog.Errorf("S3Tables: failed to encode error response: %v", err)
	}
}

// ARN generation helpers

func (h *S3TablesHandler) generateTableBucketARN(ownerAccountID, bucketName string) string {
	return fmt.Sprintf("arn:aws:s3tables:%s:%s:bucket/%s", h.region, ownerAccountID, bucketName)
}

func (h *S3TablesHandler) generateTableARN(ownerAccountID, bucketName, tableID string) string {
	return fmt.Sprintf("arn:aws:s3tables:%s:%s:bucket/%s/table/%s", h.region, ownerAccountID, bucketName, tableID)
}

func isAuthError(err error) bool {
	var authErr *AuthError
	return errors.As(err, &authErr) || errors.Is(err, ErrAccessDenied)
}

func (h *S3TablesHandler) readTags(ctx context.Context, client filer_pb.SeaweedFilerClient, path string) (map[string]string, error) {
	data, err := h.getExtendedAttribute(ctx, client, path, ExtendedKeyTags)
	if err != nil {
		if errors.Is(err, ErrAttributeNotFound) {
			return nil, nil
		}
		return nil, err
	}
	tags := make(map[string]string)
	if err := json.Unmarshal(data, &tags); err != nil {
		return nil, fmt.Errorf("failed to unmarshal tags: %w", err)
	}
	return tags, nil
}

func mapKeys(tags map[string]string) []string {
	if len(tags) == 0 {
		return nil
	}
	keys := make([]string, 0, len(tags))
	for key := range tags {
		keys = append(keys, key)
	}
	return keys
}