package functions

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"strconv"

	"github.com/DeBrosOfficial/network/pkg/cli/shared"
	"gopkg.in/yaml.v3"
)

// FunctionConfig represents the function.yaml configuration.
type FunctionConfig struct {
	Name    string            `yaml:"name"`
	Public  bool              `yaml:"public"`
	Memory  int               `yaml:"memory"`
	Timeout int               `yaml:"timeout"`
	Retry   RetryConfig       `yaml:"retry"`
	Env     map[string]string `yaml:"env"`
}

// RetryConfig holds retry settings.
type RetryConfig struct {
	Count int `yaml:"count"`
	Delay int `yaml:"delay"`
}

// wasmMagicBytes is the WASM binary magic number: \0asm
var wasmMagicBytes = []byte{0x00, 0x61, 0x73, 0x6d}

// validNameRegex validates function names (alphanumeric, hyphens, underscores).
var validNameRegex = regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9_-]*$`)

// LoadConfig reads and parses a function.yaml from the given directory.
func LoadConfig(dir string) (*FunctionConfig, error) {
	path := filepath.Join(dir, "function.yaml")
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read function.yaml: %w", err)
	}

	var cfg FunctionConfig
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("failed to parse function.yaml: %w", err)
	}

	// Apply defaults
	if cfg.Memory == 0 {
		cfg.Memory = 64
	}
	if cfg.Timeout == 0 {
		cfg.Timeout = 30
	}
	if cfg.Retry.Delay == 0 {
		cfg.Retry.Delay = 5
	}

	// Validate
	if cfg.Name == "" {
		return nil, fmt.Errorf("function.yaml: 'name' is required")
	}
	if !validNameRegex.MatchString(cfg.Name) {
		return nil, fmt.Errorf("function.yaml: 'name' must start with a letter and contain only letters, digits, hyphens, or underscores")
	}
	if cfg.Memory < 1 || cfg.Memory > 256 {
		return nil, fmt.Errorf("function.yaml: 'memory' must be between 1 and 256 MB (got %d)", cfg.Memory)
	}
	if cfg.Timeout < 1 || cfg.Timeout > 300 {
		return nil, fmt.Errorf("function.yaml: 'timeout' must be between 1 and 300 seconds (got %d)", cfg.Timeout)
	}

	return &cfg, nil
}

// ValidateWASM checks that the given bytes are a valid WASM binary (magic number check).
func ValidateWASM(data []byte) error {
	if len(data) < 8 {
		return fmt.Errorf("file too small to be a valid WASM binary (%d bytes)", len(data))
	}
	if !bytes.HasPrefix(data, wasmMagicBytes) {
		return fmt.Errorf("file is not a valid WASM binary (bad magic bytes)")
	}
	return nil
}

// ValidateWASMFile checks that the file at the given path is a valid WASM binary.
func ValidateWASMFile(path string) error {
	f, err := os.Open(path)
	if err != nil {
		return fmt.Errorf("failed to open WASM file: %w", err)
	}
	defer f.Close()

	header := make([]byte, 8)
	n, err := f.Read(header)
	if err != nil {
		return fmt.Errorf("failed to read WASM file: %w", err)
	}
	return ValidateWASM(header[:n])
}

// apiRequest performs an authenticated HTTP request to the gateway API.
func apiRequest(method, endpoint string, body io.Reader, contentType string) (*http.Response, error) {
	apiURL := shared.GetAPIURL()
	url := apiURL + endpoint

	req, err := http.NewRequest(method, url, body)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	if contentType != "" {
		req.Header.Set("Content-Type", contentType)
	}

	token, err := shared.GetAuthToken()
	if err != nil {
		return nil, fmt.Errorf("authentication required: %w", err)
	}
	req.Header.Set("Authorization", "Bearer "+token)

	return http.DefaultClient.Do(req)
}

// apiGet performs an authenticated GET request and returns the parsed JSON response.
func apiGet(endpoint string) (map[string]interface{}, error) {
	resp, err := apiRequest("GET", endpoint, nil, "")
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API error (%d): %s", resp.StatusCode, string(respBody))
	}

	var result map[string]interface{}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	return result, nil
}

// apiDelete performs an authenticated DELETE request and returns the parsed JSON response.
func apiDelete(endpoint string) (map[string]interface{}, error) {
	resp, err := apiRequest("DELETE", endpoint, nil, "")
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API error (%d): %s", resp.StatusCode, string(respBody))
	}

	var result map[string]interface{}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	return result, nil
}

// uploadWASMFunction uploads a WASM file to the deploy endpoint via multipart/form-data.
func uploadWASMFunction(wasmPath string, cfg *FunctionConfig) (map[string]interface{}, error) {
	wasmFile, err := os.Open(wasmPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open WASM file: %w", err)
	}
	defer wasmFile.Close()

	body := &bytes.Buffer{}
	writer := multipart.NewWriter(body)

	// Add form fields
	writer.WriteField("name", cfg.Name)
	writer.WriteField("is_public", strconv.FormatBool(cfg.Public))
	writer.WriteField("memory_limit_mb", strconv.Itoa(cfg.Memory))
	writer.WriteField("timeout_seconds", strconv.Itoa(cfg.Timeout))
	writer.WriteField("retry_count", strconv.Itoa(cfg.Retry.Count))
	writer.WriteField("retry_delay_seconds", strconv.Itoa(cfg.Retry.Delay))

	// Add env vars as metadata JSON
	if len(cfg.Env) > 0 {
		metadata, _ := json.Marshal(map[string]interface{}{
			"env_vars": cfg.Env,
		})
		writer.WriteField("metadata", string(metadata))
	}

	// Add WASM file
	part, err := writer.CreateFormFile("wasm", filepath.Base(wasmPath))
	if err != nil {
		return nil, fmt.Errorf("failed to create form file: %w", err)
	}
	if _, err := io.Copy(part, wasmFile); err != nil {
		return nil, fmt.Errorf("failed to write WASM data: %w", err)
	}
	writer.Close()

	resp, err := apiRequest("POST", "/v1/functions", body, writer.FormDataContentType())
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("deploy failed (%d): %s", resp.StatusCode, string(respBody))
	}

	var result map[string]interface{}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	return result, nil
}

// ResolveFunctionDir resolves and validates a function directory.
// If dir is empty, uses the current working directory.
func ResolveFunctionDir(dir string) (string, error) {
	if dir == "" {
		dir = "."
	}
	absDir, err := filepath.Abs(dir)
	if err != nil {
		return "", fmt.Errorf("failed to resolve path: %w", err)
	}
	info, err := os.Stat(absDir)
	if err != nil {
		return "", fmt.Errorf("directory does not exist: %w", err)
	}
	if !info.IsDir() {
		return "", fmt.Errorf("%s is not a directory", absDir)
	}
	return absDir, nil
}