package utils

import (
	"bytes"
	"context"
	"crypto/rand"
	"crypto/tls"
	"encoding/hex"
	"encoding/json"
	"encoding/xml"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"reflect"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/private/protocol/xml/xmlutil"
	"github.com/aws/aws-sdk-go/service/ec2"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/mulgadc/hive/hive/awserrors"
	"github.com/mulgadc/hive/hive/config"
	"github.com/pterm/pterm"
	"golang.org/x/net/http2"
)

// GenerateResourceID generates a unique resource ID with the given prefix.
// Format: {prefix}-{17 hex chars} using crypto/rand.
func GenerateResourceID(prefix string) string {
	b := make([]byte, 9)
	if _, err := rand.Read(b); err != nil {
		panic("crypto/rand failed: " + err.Error())
	}
	return prefix + "-" + hex.EncodeToString(b)[:17]
}

// Convert interface to XML
func MarshalToXML(payload any) ([]byte, error) {

	var buf bytes.Buffer
	enc := xml.NewEncoder(&buf)

	if err := xmlutil.BuildXML(payload, enc); err != nil {
		slog.Error("BuildXML failed", "err", err)
		return nil, err
	}

	if err := enc.Flush(); err != nil {
		slog.Error("Flush failed", "err", err)
		return nil, err
	}

	return buf.Bytes(), nil

}

// wrapWithLocation decorates payload with the requested locationName tag.
func GenerateXMLPayload(locationName string, payload any) any {
	t := reflect.StructOf([]reflect.StructField{
		{
			Name: "Value",
			Type: reflect.TypeOf(payload),
			Tag:  reflect.StructTag(`locationName:"` + locationName + `"`),
		},
	})

	v := reflect.New(t).Elem()
	v.Field(0).Set(reflect.ValueOf(payload))
	return v.Interface()
}

// GenerateIAMXMLPayload wraps IAM output with proper *Result element structure.
// IAM responses have format: <ActionResponse><ActionResult>content</ActionResult><ResponseMetadata>...</ResponseMetadata></ActionResponse>
func GenerateIAMXMLPayload(action string, payload any) any {
	// First wrap with ActionResult (e.g., CreateUserResult)
	resultName := action + "Result"
	resultWrapper := reflect.StructOf([]reflect.StructField{
		{
			Name: "Result",
			Type: reflect.TypeOf(payload),
			Tag:  reflect.StructTag(`locationName:"` + resultName + `"`),
		},
	})
	resultV := reflect.New(resultWrapper).Elem()
	resultV.Field(0).Set(reflect.ValueOf(payload))

	// Then wrap with ActionResponse (e.g., CreateUserResponse)
	responseName := action + "Response"
	responseWrapper := reflect.StructOf([]reflect.StructField{
		{
			Name: "Response",
			Type: resultWrapper,
			Tag:  reflect.StructTag(`locationName:"` + responseName + `"`),
		},
	})
	responseV := reflect.New(responseWrapper).Elem()
	responseV.Field(0).Set(resultV)

	return responseV.Interface()
}

// Generate JSON Error Payload
func GenerateErrorPayload(code string) (jsonResponse []byte) {

	var responseError ec2.ResponseError
	responseError.Code = aws.String(code)

	// Return as JSON, to simulate the NATS response
	jsonResponse, err := json.Marshal(responseError)
	if err != nil {
		slog.Error("GenerateErrorPayload could not marshal JSON payload", "err", err)
		return nil
	}

	return

}

// Validate the payload is an ec2.ResponseError
func ValidateErrorPayload(payload []byte) (responseError ec2.ResponseError, err error) {

	decoder := json.NewDecoder(bytes.NewReader(payload))
	decoder.DisallowUnknownFields()

	err = decoder.Decode(&responseError)

	if err == nil && responseError.Code != nil {
		// Successfully decoded as ResponseError AND has a non-nil Code field
		// This is a real error response
		return responseError, errors.New("ResponseError detected")
	}

	// Either failed to decode (not an error structure) or Code is nil (empty valid response)
	return responseError, nil

}

// Unmarshal payload

func UnmarshalJsonPayload(input any, jsonData []byte) []byte {

	decoder := json.NewDecoder(bytes.NewReader(jsonData))
	decoder.DisallowUnknownFields()

	// input is already a pointer, don't take address again
	err := decoder.Decode(input)
	if err != nil {
		return GenerateErrorPayload(awserrors.ErrorValidationError)
	}

	return nil

}

func MarshalJsonPayload(input any, jsonData []byte) []byte {

	decoder := json.NewDecoder(bytes.NewReader(jsonData))
	decoder.DisallowUnknownFields()

	// input is already a pointer, don't take address again
	err := decoder.Decode(input)
	if err != nil {
		return GenerateErrorPayload(awserrors.ErrorValidationError)
	}

	return nil

}

// ValidateKeyPairName validates that a key pair name only contains allowed characters:
// - Uppercase A-Z
// - Lowercase a-z
// - Digits 0-9
// - Hyphen (-)
// - Underscore (_)
// - Period (.)
// This prevents path traversal attacks and invalid characters like /etc/passwd, ../../../, etc.
// Returns ErrorInvalidKeyPairFormat if validation fails
func ValidateKeyPairName(name string) error {
	if name == "" {
		return errors.New("key name cannot be empty")
	}

	// Check each character is in the allowed set
	for _, char := range name {
		valid := (char >= 'A' && char <= 'Z') ||
			(char >= 'a' && char <= 'z') ||
			(char >= '0' && char <= '9') ||
			char == '-' ||
			char == '_' ||
			char == '.'

		if !valid {
			return errors.New(awserrors.ErrorInvalidKeyPairFormat)
		}
	}

	return nil
}

func CreateS3Client(cfg *config.Config) *s3.S3 {

	tr := &http.Transport{
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: true,
			NextProtos:         []string{"h2", "http/1.1"},
		},
		ForceAttemptHTTP2: true,
	}

	// CRITICAL: Configure HTTP/2 support with custom TLS config
	if err := http2.ConfigureTransport(tr); err != nil {
		slog.Warn("Failed to configure HTTP/2", "error", err)
	}

	httpClient := &http.Client{Transport: tr}

	sess := session.Must(session.NewSession(&aws.Config{
		Region:           aws.String(cfg.Predastore.Region),
		Endpoint:         aws.String(fmt.Sprintf("https://%s", cfg.Predastore.Host)),
		Credentials:      credentials.NewStaticCredentials(cfg.Predastore.AccessKey, cfg.Predastore.SecretKey, ""),
		S3ForcePathStyle: aws.Bool(true),
		DisableSSL:       aws.Bool(false),
		HTTPClient:       httpClient,
	}))

	return s3.New(sess)

}

// Download helper

func DownloadFileWithProgress(url string, name string, filename string, timeout time.Duration) (err error) {

	// Context with optional timeout and Ctrl+C cancel
	ctx, cancel := context.WithCancel(context.Background())
	if timeout > 0 {
		ctx, cancel = context.WithTimeout(ctx, timeout)
	}
	defer cancel()
	intCh := make(chan os.Signal, 1)
	signal.Notify(intCh, os.Interrupt)
	go func() {
		<-intCh
		cancel()
	}()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return fmt.Errorf("request error: %v", err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return fmt.Errorf("http error: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode > 299 {
		return fmt.Errorf("unexpected status: %s", resp.Status)
	}

	f, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("file create error: %v", err)
	}
	defer f.Close()

	cl := resp.ContentLength

	// Known size: progress bar with total
	if cl > 0 {
		bar, _ := pterm.DefaultProgressbar.
			WithTitle(fmt.Sprintf("Downloading %s", name)).
			WithTotal(int(cl)).
			Start()

		var written int64
		reader := io.TeeReader(resp.Body, progressWriter(func(n int) {
			written += int64(n)
			// Update progress bar with the number of bytes read in this chunk
			bar.Add(n)
		}))

		_, err = io.Copy(f, reader)
		_, _ = bar.Stop()
		if err != nil {
			return fmt.Errorf("copy error: %v", err)
		}

		pterm.Printf("Saved %s (%s)\n", filename, humanBytes(SafeInt64ToUint64(written)))
		return

	} else {

		// Unknown size: spinner that shows bytes downloaded
		spin, _ := pterm.DefaultSpinner.
			WithText("Downloading (size unknown)...").
			Start()
		var written int64
		reader := io.TeeReader(resp.Body, progressWriter(func(n int) {
			written += int64(n)
			spin.UpdateText(fmt.Sprintf("Downloading %s (%s) ...", name, humanBytes(SafeInt64ToUint64(written))))
		}))
		_, err = io.Copy(f, reader)
		_ = spin.Stop()

		if err != nil {
			return fmt.Errorf("copy error: %v", err)
		}

		pterm.Printf("Saved %s (%s)\n", filename, humanBytes(SafeInt64ToUint64(written)))

	}

	return nil
}

// progressWriter turns byte counts into a callback for UI updates.
type progressWriter func(n int)

func (pw progressWriter) Write(p []byte) (int, error) {
	pw(len(p))
	return len(p), nil
}

func humanBytes(b uint64) string {
	const unit = 1024
	if b < unit {
		return fmt.Sprintf("%d B", b)
	}
	div, exp := uint64(unit), 0
	for n := b / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(b)/float64(div), "KMGTPEZY"[exp])
}

func dirExists(path string) bool {
	info, err := os.Stat(path)
	if os.IsNotExist(err) {
		return false
	}
	if err != nil {
		return false
	}
	return info.IsDir()
}