package browser

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/go-rod/rod"
	"github.com/go-rod/rod/lib/launcher"
	"github.com/go-rod/rod/lib/proto"
	"github.com/go-rod/stealth"
	"trankilou.fr/lassistanoque/backend/internal/domain"
)

type BrowserConfig struct {
	// Headless est un pointeur pour distinguer "non renseigné" (défaut : true) de "explicitement false".
	Headless       *bool `yaml:"headless"`
	TimeoutSeconds int   `yaml:"timeoutSeconds"`
}

// BrowserTool maintains a persistent browser session across LLM tool calls.
type BrowserTool struct{}

var (
	browserInstance  *rod.Browser
	currentPage      *rod.Page
	browserMu        sync.Mutex
	launchedHeadless bool
)

func (t *BrowserTool) Name() string {
	return "browser"
}

func (t *BrowserTool) Description() string {
	return "Control a web browser to navigate pages and interact with content. " +
		"Maintains session state across calls (cookies, current page). " +
		"Actions: 'navigate' (go to URL), 'click' (click element by CSS selector), " +
		"'fill' (type into an input field), 'content' (get current page text), " +
		"'links' (list all links on current page)."
}

func (t *BrowserTool) Params() []domain.ToolParam {
	return []domain.ToolParam{
		{JsonName: "headless", Type: "bool", Mandatory: true, Description: "Headless"},
		{JsonName: "timeoutSeconds", Type: "int", Mandatory: true, Description: "Timeout en secondes"},
	}
}

func (t *BrowserTool) Definition(ctx context.Context) *domain.ToolDefinition {
	return &domain.ToolDefinition{
		Type: "function",
		Function: &domain.ToolFunction{
			Name:        t.Name(),
			Description: t.Description(),
			Parameters: map[string]any{
				"type": "object",
				"properties": map[string]any{
					"action": map[string]any{
						"type":        "string",
						"enum":        []string{"navigate", "click", "fill", "content", "links"},
						"description": "The browser action to perform.",
					},
					"url": map[string]any{
						"type":        "string",
						"description": "URL to navigate to. Required for action='navigate'.",
					},
					"selector": map[string]any{
						"type":        "string",
						"description": "CSS selector of the element to interact with. Required for 'click' and 'fill'.",
					},
					"value": map[string]any{
						"type":        "string",
						"description": "Text value to type into the field. Required for action='fill'.",
					},
				},
				"required": []string{"action"},
			},
		},
	}
}

func (t *BrowserTool) Execute(_ context.Context, input []byte, configuration string) ([]byte, error) {

	slog.Debug("[browser]", "input", string(input))

	var params struct {
		Action   string `json:"action"`
		URL      string `json:"url"`
		Selector string `json:"selector"`
		Value    string `json:"value"`
	}
	if err := json.Unmarshal(input, &params); err != nil {
		return nil, fmt.Errorf("invalid parameters: %w", err)
	}

	var toolConfig BrowserConfig
	err := json.Unmarshal([]byte(configuration), &toolConfig)
	if err != nil {
		return nil, err
	}
	timeout := time.Duration(toolConfig.TimeoutSeconds) * time.Second

	// Headless est nil quand la configuration ne le précise pas : défaut à true.
	headless := true
	if toolConfig.Headless != nil {
		headless = *toolConfig.Headless
	}

	if timeout <= 0 {
		timeout = 60 * time.Second
	}

	browserMu.Lock()
	defer browserMu.Unlock()

	if err := ensureBrowser(headless); err != nil {
		return nil, fmt.Errorf("browser init failed: %w", err)
	}

	switch params.Action {
	case "navigate":
		if params.URL == "" {
			return nil, fmt.Errorf("'url' is required for action 'navigate'")
		}
		return t.navigate(params.URL, timeout)

	case "click":
		if params.Selector == "" {
			return nil, fmt.Errorf("'selector' is required for action 'click'")
		}
		return t.click(params.Selector, timeout)

	case "fill":
		if params.Selector == "" || params.Value == "" {
			return nil, fmt.Errorf("'selector' and 'value' are required for action 'fill'")
		}
		return t.fill(params.Selector, params.Value, timeout)

	case "content":
		return t.pageContent(timeout)

	case "links":
		return t.pageLinks(timeout)

	default:
		return nil, fmt.Errorf("unknown action %q", params.Action)
	}
}

func browserProfileDir() string {
	if dir, err := os.UserCacheDir(); err == nil {
		return filepath.Join(dir, "lassistanoque", "browser-profile")
	}
	return filepath.Join(os.TempDir(), "lassistanoque-browser-profile")
}

// ensureBrowser lance le navigateur au premier appel et le relance si le mode
// headless a changé dans la configuration.
func ensureBrowser(headless bool) error {
	if browserInstance != nil {
		if headless == launchedHeadless {
			return nil
		}
		_ = browserInstance.Close()
		browserInstance = nil
		currentPage = nil
	}
	if err := initBrowser(headless); err != nil {
		return err
	}
	launchedHeadless = headless
	return nil
}

func initBrowser(headless bool) error {
	path, _ := launcher.LookPath()
	controlURL, err := launcher.New().
		Bin(path).
		Headless(headless).
		UserDataDir(browserProfileDir()).
		Delete("enable-automation").
		Launch()
	if err != nil {
		return fmt.Errorf("failed to launch browser: %w", err)
	}
	b := rod.New().ControlURL(controlURL)
	if err := b.Connect(); err != nil {
		return fmt.Errorf("failed to connect to browser: %w", err)
	}
	browserInstance = b
	return nil
}

func ensurePage(timeout time.Duration) error {
	if currentPage == nil {
		page, err := stealth.Page(browserInstance.Timeout(timeout))
		if err != nil {
			return fmt.Errorf("failed to open page: %w", err)
		}
		currentPage = page
	}
	return nil
}

func (t *BrowserTool) navigate(rawURL string, timeout time.Duration) ([]byte, error) {
	if err := ensurePage(timeout); err != nil {
		return nil, err
	}
	if err := currentPage.Timeout(timeout).Navigate(rawURL); err != nil {
		return nil, fmt.Errorf("navigation failed: %w", err)
	}
	if err := currentPage.Timeout(timeout).WaitLoad(); err != nil {
		return nil, fmt.Errorf("page load failed: %w", err)
	}
	return t.pageContent(timeout)
}

func (t *BrowserTool) click(selector string, timeout time.Duration) ([]byte, error) {
	if err := ensurePage(timeout); err != nil {
		return nil, err
	}
	el, err := currentPage.Timeout(timeout).Element(selector)
	if err != nil {
		return nil, fmt.Errorf("element %q not found: %w", selector, err)
	}
	if err := el.Click(proto.InputMouseButtonLeft, 1); err != nil {
		return nil, fmt.Errorf("click failed: %w", err)
	}
	if err := currentPage.WaitIdle(timeout); err != nil {
		return nil, fmt.Errorf("wait after click failed: %w", err)
	}
	return t.pageContent(timeout)
}

func (t *BrowserTool) fill(selector, value string, timeout time.Duration) ([]byte, error) {
	if err := ensurePage(timeout); err != nil {
		return nil, err
	}
	el, err := currentPage.Timeout(timeout).Element(selector)
	if err != nil {
		return nil, fmt.Errorf("element %q not found: %w", selector, err)
	}
	if err := el.SelectAllText(); err != nil {
		return nil, fmt.Errorf("failed to select text: %w", err)
	}
	if err := el.Input(value); err != nil {
		return nil, fmt.Errorf("fill failed: %w", err)
	}
	return t.pageContent(timeout)
}

func (t *BrowserTool) pageContent(timeout time.Duration) ([]byte, error) {
	if currentPage == nil {
		return []byte("No page loaded."), nil
	}

	info, err := currentPage.Info()
	if err != nil {
		return nil, fmt.Errorf("failed to get page info: %w", err)
	}

	titleRes, err := currentPage.Eval("() => document.title")
	if err != nil {
		return nil, fmt.Errorf("failed to get page title: %w", err)
	}
	title := titleRes.Value.String()

	body, err := currentPage.Timeout(timeout).Element("body")
	if err != nil {
		return nil, fmt.Errorf("failed to get page body: %w", err)
	}
	text, err := body.Text()
	if err != nil {
		return nil, fmt.Errorf("failed to extract page text: %w", err)
	}

	var sb strings.Builder
	fmt.Fprintf(&sb, "Page: %s\nURL: %s\n\n%s", title, info.URL, text)
	return []byte(sb.String()), nil
}

func (t *BrowserTool) pageLinks(timeout time.Duration) ([]byte, error) {
	if currentPage == nil {
		return []byte("No page loaded."), nil
	}

	elements, err := currentPage.Timeout(timeout).Elements("a[href]")
	if err != nil {
		return nil, fmt.Errorf("failed to get links: %w", err)
	}

	var sb strings.Builder
	fmt.Fprintf(&sb, "Links on current page (%d):\n\n", len(elements))
	for i, el := range elements {
		href, _ := el.Attribute("href")
		text, _ := el.Text()
		if href == nil {
			continue
		}
		label := strings.TrimSpace(text)
		if label == "" {
			label = "(no text)"
		}
		fmt.Fprintf(&sb, "%d. %s — %s\n", i+1, label, *href)
	}
	return []byte(sb.String()), nil
}