//go:build linux || freebsd
// +build linux freebsd

package api

import (
	"context"
	"fmt"
	"net/url"
	"time"

	"codeberg.org/petrbalvin/goget/internal/config"
	"codeberg.org/petrbalvin/goget/internal/core"
	"codeberg.org/petrbalvin/goget/internal/metalink"
	"codeberg.org/petrbalvin/goget/internal/protocol"
	"codeberg.org/petrbalvin/goget/internal/queue"
)

// Version returns the current goget version.
func Version() string {
	return core.Version
}

// Client is the public API client for goget downloads and uploads.
type Client struct {
	ctx    context.Context
	cancel context.CancelFunc
	cfg    *clientConfig
}

// ClientOption configures a Client.
type ClientOption func(*clientConfig)

type clientConfig struct {
	timeout   time.Duration
	userAgent string
	verbose   bool
}

// WithTimeout sets the request timeout.
func WithTimeout(d time.Duration) ClientOption {
	return func(c *clientConfig) {
		c.timeout = d
	}
}

// WithUserAgent sets the User-Agent header.
func WithUserAgent(ua string) ClientOption {
	return func(c *clientConfig) {
		c.userAgent = ua
	}
}

// WithVerbose enables verbose output.
func WithVerbose(v bool) ClientOption {
	return func(c *clientConfig) {
		c.verbose = v
	}
}

// NewClient creates a new goget client with the given options.
// The client registers HTTP and FTP protocol handlers automatically.
func NewClient(opts ...ClientOption) *Client {
	cfg := &clientConfig{
		timeout:   30 * time.Minute,
		userAgent: "Goget/" + Version() + " (Library)",
		verbose:   false,
	}
	for _, opt := range opts {
		opt(cfg)
	}

	registerDefaultProtocols()

	// The client-scoped context is cancellable but has no deadline. It
	// lives until Close() is called and is the parent of every per-request
	// context created by requestContext(). A deadline here would cap the
	// *lifetime* of the client, so a long-lived Client could only serve
	// requests for cfg.timeout before every subsequent call failed with
	// "context deadline exceeded". The per-request deadline is applied
	// below in Download and Upload.
	ctx, cancel := context.WithCancel(context.Background())
	return &Client{ctx: ctx, cancel: cancel, cfg: cfg}
}

// requestContext returns a child context of the client scope with the
// configured per-request timeout applied. If the timeout is zero or
// negative, the request inherits the client scope without a deadline.
func (c *Client) requestContext() (context.Context, context.CancelFunc) {
	if c.cfg.timeout > 0 {
		return context.WithTimeout(c.ctx, c.cfg.timeout)
	}
	return context.WithCancel(c.ctx)
}

// DownloadRequest represents a download request.
type DownloadRequest struct {
	URL     string
	Output  string
	Resume  bool
	Verbose bool
}

// DownloadResult contains the result of a download.
type DownloadResult struct {
	BytesDownloaded int64
	TotalSize       int64
	Speed           float64
	Duration        time.Duration
	OutputPath      string
	Protocol        string
	IPVersion       int
	Resumed         bool
	Parallel        bool
	ChunksCount     int
}

// Download downloads a file from the given URL.
func (c *Client) Download(req *DownloadRequest) (*DownloadResult, error) {
	if req == nil || req.URL == "" {
		return nil, fmt.Errorf("url is required")
	}

	parsedURL, err := url.Parse(req.URL)
	if err != nil {
		return nil, fmt.Errorf("invalid url: %w", err)
	}

	proto, err := protocol.Get(parsedURL)
	if err != nil {
		return nil, fmt.Errorf("unsupported protocol: %w", err)
	}

	// Apply client defaults if request doesn't override
	verbose := req.Verbose || c.cfg.verbose
	headers := make(map[string]string)
	if c.cfg.userAgent != "" {
		headers["User-Agent"] = c.cfg.userAgent
	}

	coreReq := &core.DownloadRequest{
		URL:     parsedURL,
		Output:  req.Output,
		Resume:  req.Resume,
		Verbose: verbose,
		Headers: headers,
		Timeout: c.cfg.timeout,
	}

	// Derive a per-request context from the client scope so a long-lived
	// Client can serve many requests and each one gets its own deadline.
	reqCtx, reqCancel := c.requestContext()
	defer reqCancel()
	coreReq.Ctx = reqCtx

	result, err := proto.Download(reqCtx, coreReq)
	if err != nil {
		return nil, err
	}

	return &DownloadResult{
		BytesDownloaded: result.BytesDownloaded,
		TotalSize:       result.TotalSize,
		Speed:           result.Speed,
		Duration:        result.Duration,
		OutputPath:      result.OutputPath,
		Protocol:        result.Protocol,
		IPVersion:       result.IPVersion,
		Resumed:         result.Resumed,
		Parallel:        result.Parallel,
		ChunksCount:     result.ChunksCount,
	}, nil
}

// UploadRequest represents an upload request.
type UploadRequest struct {
	URL      string
	FilePath string
	Method   string // PUT or POST
	Verbose  bool
}

// UploadResult contains the result of an upload.
type UploadResult struct {
	BytesUploaded int64
	Duration      time.Duration
	Protocol      string
	ResultURL     string
}

// Upload uploads a file to the given URL.
func (c *Client) Upload(req *UploadRequest) (*UploadResult, error) {
	if req == nil || req.URL == "" || req.FilePath == "" {
		return nil, fmt.Errorf("url and file path are required")
	}

	parsedURL, err := url.Parse(req.URL)
	if err != nil {
		return nil, fmt.Errorf("invalid url: %w", err)
	}

	proto, err := protocol.Get(parsedURL)
	if err != nil {
		return nil, fmt.Errorf("unsupported protocol: %w", err)
	}

	uploader, ok := proto.(core.Uploader)
	if !ok {
		return nil, fmt.Errorf("protocol does not support upload: %s", parsedURL.Scheme)
	}

	coreReq := &core.UploadRequest{
		URL:     parsedURL,
		Input:   req.FilePath,
		Verbose: req.Verbose,
	}

	// Per-request context so a long-lived Client can serve many uploads
	// without each one being bounded by the time elapsed since client
	// creation. See NewClient for the rationale.
	reqCtx, reqCancel := c.requestContext()
	defer reqCancel()

	coreResult, err := uploader.Upload(reqCtx, coreReq)
	if err != nil {
		return nil, err
	}

	return &UploadResult{
		BytesUploaded: coreResult.BytesUploaded,
		Duration:      coreResult.Duration,
		Protocol:      coreResult.Protocol,
		ResultURL:     coreResult.ResultURL,
	}, nil
}

// Close releases resources associated with the client.
func (c *Client) Close() {
	c.cancel()
}

// Download is a convenience function for a one-shot download.
func Download(urlStr, output string) (*DownloadResult, error) {
	client := NewClient()
	defer client.Close()

	return client.Download(&DownloadRequest{
		URL:    urlStr,
		Output: output,
		Resume: true,
	})
}

// Upload is a convenience function for a one-shot upload.
func Upload(urlStr, filePath, method string) (*UploadResult, error) {
	client := NewClient()
	defer client.Close()

	return client.Upload(&UploadRequest{
		URL:      urlStr,
		FilePath: filePath,
		Method:   method,
	})
}

// ============================================================================
// Queue API
// ============================================================================

// QueueClient wraps the download queue for programmatic use.
type QueueClient struct {
	q *queue.Queue
}

// NewQueueClient creates a new queue client.
func NewQueueClient(queueFile string) (*QueueClient, error) {
	q, err := queue.NewQueue(&queue.QueueConfig{QueueFile: queueFile})
	if err != nil {
		return nil, err
	}
	return &QueueClient{q: q}, nil
}

// Add adds a URL to the download queue.
func (qc *QueueClient) Add(urlStr, output string, priority int) string {
	item := qc.q.Add(urlStr, output, priority)
	return item.ID
}

// List returns all items in the queue.
func (qc *QueueClient) List() []*queue.QueueItem {
	return qc.q.GetAll()
}

// Stats returns queue statistics.
func (qc *QueueClient) Stats() queue.QueueStats {
	return qc.q.GetStats()
}

// Remove removes an item from the queue by ID.
func (qc *QueueClient) Remove(id string) bool {
	return qc.q.Remove(id)
}

// ClearCompleted removes all completed items.
func (qc *QueueClient) ClearCompleted() int {
	return qc.q.ClearCompleted()
}

// ============================================================================
// Metalink API
// ============================================================================

// ParseMetalink parses a Metalink file.
func ParseMetalink(path string) (*metalink.Metalink, error) {
	return metalink.ParseFile(path)
}

// FetchMetalink downloads and parses a Metalink from a URL.
func FetchMetalink(urlStr string) (*metalink.Metalink, error) {
	return metalink.ParseURL(urlStr)
}

// ============================================================================
// Config API
// ============================================================================

// LoadConfig loads the configuration file.
func LoadConfig(path string) (*config.Config, error) {
	return config.Load(path)
}

// DefaultConfig returns the default configuration.
func DefaultConfig() *config.Config {
	return config.DefaultConfig()
}

// ParseSpeed parses a speed string like "10MB/s" to bytes/sec.
func ParseSpeed(s string) int64 {
	return config.ParseSpeed(s)
}