package iceberg

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"strconv"
	"strings"

	"github.com/gorilla/mux"
	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3tables"
)

// parseNamespace parses the namespace from path parameter.
// Iceberg uses unit separator (0x1F) for multi-level namespaces.
// Note: mux already decodes URL-encoded path parameters, so we only split by unit separator.
func parseNamespace(encoded string) []string {
	if encoded == "" {
		return nil
	}
	parts := strings.Split(encoded, "\x1F")
	// Filter empty parts
	result := make([]string, 0, len(parts))
	for _, p := range parts {
		if p != "" {
			result = append(result, p)
		}
	}
	return result
}

// encodeNamespace encodes namespace parts using the Iceberg REST protocol's
// unit separator (0x1F) convention. This is only appropriate for protocol-level
// encoding (e.g. URL path parameters), NOT for filesystem/S3 paths.
func encodeNamespace(parts []string) string {
	return strings.Join(parts, "\x1F")
}

// flattenNamespacePath joins namespace parts with "." for use in S3 location
// and filer paths, matching the S3 Tables storage layer convention.
func flattenNamespacePath(parts []string) string {
	return strings.Join(parts, ".")
}

func parseS3Location(location string) (bucketName, tablePath string, err error) {
	if !strings.HasPrefix(location, "s3://") {
		return "", "", fmt.Errorf("unsupported location: %s", location)
	}
	trimmed := strings.TrimPrefix(location, "s3://")
	trimmed = strings.TrimSuffix(trimmed, "/")
	if trimmed == "" {
		return "", "", fmt.Errorf("invalid location: %s", location)
	}
	parts := strings.SplitN(trimmed, "/", 2)
	bucketName = parts[0]
	if bucketName == "" {
		return "", "", fmt.Errorf("invalid location bucket: %s", location)
	}
	if len(parts) == 2 {
		tablePath = parts[1]
	}
	return bucketName, tablePath, nil
}

func tableLocationFromMetadataLocation(metadataLocation string) string {
	trimmed := strings.TrimSuffix(metadataLocation, "/")
	if idx := strings.LastIndex(trimmed, "/metadata/"); idx != -1 {
		return trimmed[:idx]
	}
	return trimmed
}

// writeJSON writes a JSON response.
func writeJSON(w http.ResponseWriter, status int, v interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if v != nil {
		data, err := json.Marshal(v)
		if err != nil {
			glog.Errorf("Iceberg: failed to encode response: %v", err)
			return
		}
		w.Write(data)
	}
}

// writeError writes an Iceberg error response.
func writeError(w http.ResponseWriter, status int, errType, message string) {
	resp := ErrorResponse{
		Error: ErrorModel{
			Message: message,
			Type:    errType,
			Code:    status,
		},
	}
	writeJSON(w, status, resp)
}

// nameValidationError reports whether err is an S3 Tables namespace or table
// name validation failure. Such names are client input (the S3 Tables charset
// is stricter than the Iceberg REST spec), so the catalog answers 400 rather
// than treating it as a server fault.
func nameValidationError(err error) bool {
	if err == nil {
		return false
	}
	// Match the validator's own phrasings rather than a bare "namespace name"/
	// "table name" so unrelated faults (e.g. "failed to resolve table name")
	// aren't misreported as client errors. Lowercased for resilience to
	// capitalization changes.
	msg := strings.ToLower(err.Error())
	for _, marker := range []string{
		"invalid namespace name", "namespace name must", "namespace name cannot",
		"invalid table name", "table name must", "table name cannot",
	} {
		if strings.Contains(msg, marker) {
			return true
		}
	}
	return false
}

// writeManagerError maps a residual s3tables manager error to a response:
// name validation failures are client errors (400); anything else is a server
// fault (500).
func writeManagerError(w http.ResponseWriter, err error) {
	if nameValidationError(err) {
		writeError(w, http.StatusBadRequest, "BadRequestException", err.Error())
		return
	}
	writeError(w, http.StatusInternalServerError, "InternalServerError", err.Error())
}

// getBucketFromPrefix extracts table bucket name from prefix parameter.
// For now, we use the prefix as the table bucket name.
//
// The Iceberg REST spec lets clients identify a catalog either by embedding
// its prefix in the URL (/v1/{prefix}/...) or by passing ?warehouse=s3://
// <bucket>/ as a query parameter. Clients that skip the /v1/config handshake
// (or ignore its overrides) still routinely send the warehouse parameter on
// every request, so honor it as a fallback before the env-var default.
// See issue #9103.
func getBucketFromPrefix(r *http.Request) string {
	vars := mux.Vars(r)
	if prefix := vars["prefix"]; prefix != "" {
		return prefix
	}
	if warehouse := strings.TrimSpace(r.URL.Query().Get("warehouse")); warehouse != "" {
		if bucket, _, err := parseS3Location(warehouse); err == nil && bucket != "" {
			return bucket
		}
	}
	if bucket := os.Getenv("S3TABLES_DEFAULT_BUCKET"); bucket != "" {
		return bucket
	}
	// Default bucket if no prefix - use "warehouse" for Iceberg
	return "warehouse"
}

// buildTableBucketARN builds an ARN for a table bucket.
func buildTableBucketARN(bucketName string) string {
	arn, _ := s3tables.BuildBucketARN(s3tables.DefaultRegion, s3_constants.AccountAdminId, bucketName)
	return arn
}

const (
	defaultListPageSize = 1000
	maxListPageSize     = 1000
)

func getPaginationQueryParam(r *http.Request, primary, fallback string) string {
	if v := strings.TrimSpace(r.URL.Query().Get(primary)); v != "" {
		return v
	}
	return strings.TrimSpace(r.URL.Query().Get(fallback))
}

func parsePagination(r *http.Request) (pageToken string, pageSize int, err error) {
	pageToken = getPaginationQueryParam(r, "pageToken", "page-token")
	pageSize = defaultListPageSize

	pageSizeValue := getPaginationQueryParam(r, "pageSize", "page-size")
	if pageSizeValue == "" {
		return pageToken, pageSize, nil
	}

	parsedPageSize, parseErr := strconv.Atoi(pageSizeValue)
	if parseErr != nil || parsedPageSize <= 0 {
		return pageToken, 0, fmt.Errorf("invalid pageSize %q: must be a positive integer", pageSizeValue)
	}
	if parsedPageSize > maxListPageSize {
		return pageToken, 0, fmt.Errorf("invalid pageSize %q: must be <= %d", pageSizeValue, maxListPageSize)
	}

	return pageToken, parsedPageSize, nil
}

func normalizeNamespaceProperties(properties map[string]string) map[string]string {
	if properties == nil {
		return map[string]string{}
	}
	return properties
}

// namespaceLocationProperty is the well-known Iceberg key used to advertise a
// default base path for tables created in a namespace.
const namespaceLocationProperty = "location"

// defaultNamespaceLocation returns the s3 path under which tables in the
// namespace should be stored when the namespace itself does not carry an
// explicit "location" property. The flattened namespace path mirrors the on-
// disk layout used by handleCreateTable so a deferred client-side commit ends
// up at the same place a server-computed one would.
func defaultNamespaceLocation(bucket string, namespace []string) string {
	if bucket == "" || len(namespace) == 0 {
		return ""
	}
	return fmt.Sprintf("s3://%s/%s", bucket, flattenNamespacePath(namespace))
}

// withDefaultNamespaceLocation populates the Iceberg "location" property on a
// namespace response when the storage layer does not carry one. Trino's REST
// catalog falls back to an eager createTable code path when the namespace
// has no location, which races our metadata write against Trino's emptiness
// check and surfaces as a "Cannot create a table on a non-empty location"
// error on the very first CREATE TABLE. Advertising a default location lets
// Trino take the deferred-transaction path and pick a unique per-table path.
// See issue #9074.
func withDefaultNamespaceLocation(properties map[string]string, bucket string, namespace []string) map[string]string {
	properties = normalizeNamespaceProperties(properties)
	if _, ok := properties[namespaceLocationProperty]; ok {
		return properties
	}
	if def := defaultNamespaceLocation(bucket, namespace); def != "" {
		properties[namespaceLocationProperty] = def
	}
	return properties
}