package shelfmark

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"mime"
	"net/http"
	"net/http/cookiejar"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"time"
)

// closeBody closes an HTTP response body and wraps any error.
func closeBody(body io.ReadCloser) error {
	if err := body.Close(); err != nil {
		return fmt.Errorf("failed to close response body: %w", err)
	}
	return nil
}

// Client is an HTTP client for interacting with the Shelfmark server API.
type Client struct {
	baseURL    string
	username   string
	password   string
	httpClient *http.Client

	mu            sync.Mutex
	authenticated bool
}

// NewClient creates a new Shelfmark API client.
func NewClient(baseURL, username, password string) *Client {
	jar, _ := cookiejar.New(nil)
	return &Client{
		baseURL:  strings.TrimRight(baseURL, "/"),
		username: username,
		password: password,
		httpClient: &http.Client{
			Jar:     jar,
			Timeout: 30 * time.Second,
		},
	}
}

// UpdateCredentials updates the client's base URL and credentials.
// This is called when the plugin configuration changes.
func (c *Client) UpdateCredentials(baseURL, username, password string) {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.baseURL = strings.TrimRight(baseURL, "/")
	c.username = username
	c.password = password
	c.authenticated = false

	// Reset cookie jar on credential change.
	jar, _ := cookiejar.New(nil)
	c.httpClient.Jar = jar
}

// ensureAuthenticated logs in to the Shelfmark server if not already authenticated.
func (c *Client) ensureAuthenticated() error {
	c.mu.Lock()
	defer c.mu.Unlock()

	if c.authenticated {
		return nil
	}

	return c.loginLocked()
}

// loginLocked performs authentication. Must be called with c.mu held.
func (c *Client) loginLocked() (err error) {
	// First check if auth is required.
	authCheck, err := c.checkAuthLocked()
	if err != nil {
		return fmt.Errorf("failed to check auth status: %w", err)
	}

	if !authCheck.AuthRequired {
		// No authentication needed; mark as authenticated.
		c.authenticated = true
		return nil
	}

	if c.username == "" || c.password == "" {
		return fmt.Errorf("shelfmark requires authentication but no credentials are configured")
	}

	body, err := json.Marshal(map[string]any{
		"username":    c.username,
		"password":    c.password,
		"remember_me": true,
	})
	if err != nil {
		return fmt.Errorf("failed to marshal login request: %w", err)
	}

	resp, err := c.httpClient.Post(c.baseURL+"/api/auth/login", "application/json", bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("login request failed: %w", err)
	}
	defer func() {
		if cerr := resp.Body.Close(); err == nil && cerr != nil {
			err = fmt.Errorf("failed to close response body: %w", cerr)
		}
	}()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("login failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	c.authenticated = true
	return nil
}

// checkAuthLocked checks if the Shelfmark server requires authentication. Must be called with c.mu held.
func (c *Client) checkAuthLocked() (_ *AuthCheckResponse, err error) {
	resp, err := c.httpClient.Get(c.baseURL + "/api/auth/check")
	if err != nil {
		return nil, fmt.Errorf("auth check request failed: %w", err)
	}
	defer func() {
		if cerr := resp.Body.Close(); err == nil && cerr != nil {
			err = fmt.Errorf("failed to close response body: %w", cerr)
		}
	}()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("auth check returned status %d", resp.StatusCode)
	}

	var result AuthCheckResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode auth check response: %w", err)
	}

	return &result, nil
}

// doRequest performs an HTTP request with authentication handling.
// If a 401 is received, it re-authenticates and retries once.
// The body parameter is a byte slice so it can be replayed on retry.
func (c *Client) doRequest(ctx context.Context, method, path string, body []byte) (*http.Response, error) {
	if err := c.ensureAuthenticated(); err != nil {
		return nil, err
	}

	// Read baseURL under lock to avoid race with UpdateCredentials.
	c.mu.Lock()
	baseURL := c.baseURL
	c.mu.Unlock()

	reqURL := baseURL + path

	var bodyReader io.Reader
	if body != nil {
		bodyReader = bytes.NewReader(body)
	}

	req, err := http.NewRequestWithContext(ctx, method, reqURL, bodyReader)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}

	// On 401, attempt re-authentication and retry.
	if resp.StatusCode == http.StatusUnauthorized {
		if err := resp.Body.Close(); err != nil {
			return nil, fmt.Errorf("failed to close response body: %w", err)
		}

		c.mu.Lock()
		c.authenticated = false
		err := c.loginLocked()
		c.mu.Unlock()

		if err != nil {
			return nil, fmt.Errorf("re-authentication failed: %w", err)
		}

		// Create a fresh body reader for the retry.
		var retryBody io.Reader
		if body != nil {
			retryBody = bytes.NewReader(body)
		}

		// Retry the request.
		req, err = http.NewRequestWithContext(ctx, method, reqURL, retryBody)
		if err != nil {
			return nil, fmt.Errorf("failed to create retry request: %w", err)
		}
		if body != nil {
			req.Header.Set("Content-Type", "application/json")
		}

		resp, err = c.httpClient.Do(req)
		if err != nil {
			return nil, fmt.Errorf("retry request failed: %w", err)
		}
	}

	return resp, nil
}

// Ping checks that the Shelfmark server is reachable by hitting the
// lightweight /api/auth/check endpoint. It does not require authentication.
func (c *Client) Ping() error {
	c.mu.Lock()
	baseURL := c.baseURL
	c.mu.Unlock()

	resp, err := c.httpClient.Get(baseURL + "/api/auth/check")
	if err != nil {
		return fmt.Errorf("shelfmark server unreachable: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("shelfmark server returned status %d", resp.StatusCode)
	}

	return nil
}

// SearchBooks searches for books using the Shelfmark metadata search API.
// It returns at most one result; use SearchBooksWithLimit for multiple results.
func (c *Client) SearchBooks(query string) (*SearchResponse, error) {
	return c.SearchBooksWithLimit(query, 1)
}

// SearchBooksWithLimit searches for books with a configurable result limit.
func (c *Client) SearchBooksWithLimit(query string, limit int) (_ *SearchResponse, err error) {
	params := url.Values{}
	params.Set("query", query)
	params.Set("limit", strconv.Itoa(limit))

	resp, err := c.doRequest(context.Background(), "GET", "/api/metadata/search?"+params.Encode(), nil)
	if err != nil {
		return nil, fmt.Errorf("search request failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("search failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	var result SearchResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode search response: %w", err)
	}

	return &result, nil
}

// GetReleases gets available releases (downloadable files) for a book.
// If languages is non-empty, it is passed as a filter (e.g., "en" or "en,es").
func (c *Client) GetReleases(provider, bookID, languages string) (_ *ReleasesResponse, err error) {
	params := url.Values{}
	params.Set("provider", provider)
	params.Set("book_id", bookID)
	if languages != "" {
		params.Set("languages", languages)
	}

	resp, err := c.doRequest(context.Background(), "GET", "/api/releases?"+params.Encode(), nil)
	if err != nil {
		return nil, fmt.Errorf("releases request failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("get releases failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	var result ReleasesResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode releases response: %w", err)
	}

	return &result, nil
}

// QueueDownload queues a release for download on the Shelfmark server.
func (c *Client) QueueDownload(release *Release) (_ *QueueResponse, err error) {
	body, err := json.Marshal(release)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal release: %w", err)
	}

	resp, err := c.doRequest(context.Background(), "POST", "/api/releases/download", body)
	if err != nil {
		return nil, fmt.Errorf("queue download request failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("queue download failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	var result QueueResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode queue response: %w", err)
	}

	return &result, nil
}

// StatusResponse represents the Shelfmark /api/status response.
// The response is grouped by status category:
//
//	{
//	  "complete":    { "<taskID>": { ...task... }, ... },
//	  "queued":      { "<taskID>": { ...task... }, ... },
//	  "downloading": { "<taskID>": { ...task... }, ... },
//	  "error":       { "<taskID>": { ...task... }, ... },
//	  "cancelled":   { "<taskID>": { ...task... }, ... },
//	  "locating":    { "<taskID>": { ...task... }, ... },
//	  "resolving":   { "<taskID>": { ...task... }, ... },
//	}
type statusResponse map[string]map[string]json.RawMessage

// GetStatus retrieves the current download queue status.
func (c *Client) GetStatus() (_ statusResponse, err error) {
	resp, err := c.doRequest(context.Background(), "GET", "/api/status", nil)
	if err != nil {
		return nil, fmt.Errorf("status request failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("get status failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	var result statusResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode status response: %w", err)
	}

	return result, nil
}

// GetTaskStatus searches for a task by its source_id across all status categories.
// Returns the category name (e.g. "complete", "error", "queued", "downloading")
// and whether the task was found.
func GetTaskStatus(status statusResponse, taskID string) (string, bool) {
	for category, tasks := range status {
		if _, exists := tasks[taskID]; exists {
			return category, true
		}
	}
	return "", false
}

// DownloadFile downloads a completed book file from the Shelfmark server.
// Returns the file data, filename, and any error.
func (c *Client) DownloadFile(taskID string) (_ []byte, _ string, err error) {
	params := url.Values{}
	params.Set("id", taskID)

	// Use a per-request timeout instead of mutating the shared httpClient.Timeout.
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
	defer cancel()

	resp, err := c.doRequest(ctx, "GET", "/api/localdownload?"+params.Encode(), nil)
	if err != nil {
		return nil, "", fmt.Errorf("download request failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, "", fmt.Errorf("download failed (status %d): %s", resp.StatusCode, string(respBody))
	}

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

	// Extract filename from Content-Disposition header.
	filename := ""
	if cd := resp.Header.Get("Content-Disposition"); cd != "" {
		_, params, err := mime.ParseMediaType(cd)
		if err == nil {
			filename = params["filename"]
		}
	}

	if filename == "" {
		filename = taskID
	}

	return data, filename, nil
}

// DownloadCover downloads a cover image from the Shelfmark server.
// The coverPath should be the path portion of the cover URL (e.g., /api/covers/...).
func (c *Client) DownloadCover(coverPath string) (_ []byte, _ string, err error) {
	// The cover URL from search results is relative to the Shelfmark base URL.
	resp, err := c.doRequest(context.Background(), "GET", coverPath, nil)
	if err != nil {
		return nil, "", fmt.Errorf("cover download failed: %w", err)
	}
	defer func() { err = errors.Join(err, closeBody(resp.Body)) }()

	if resp.StatusCode != http.StatusOK {
		return nil, "", fmt.Errorf("cover download returned status %d", resp.StatusCode)
	}

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

	// Determine a filename from the content type.
	contentType := resp.Header.Get("Content-Type")
	ext := ".jpg"
	switch {
	case strings.Contains(contentType, "png"):
		ext = ".png"
	case strings.Contains(contentType, "gif"):
		ext = ".gif"
	case strings.Contains(contentType, "webp"):
		ext = ".webp"
	}

	return data, "cover" + ext, nil
}