package browserbridge

import (
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"runtime"
	"strings"

	"git.julianfamily.org/keepassgo/internal/grpcaddr"
	keepassgov1 "git.julianfamily.org/keepassgo/proto/keepassgo/v1"
)

const (
	NativeHostName       = "com.keepassgo.browser"
	defaultFirefoxID     = "browser@keepassgo.com"
	maxNativeMessageSize = 1024 * 1024
	chromiumIDBytes      = 16
)

type Request struct {
	Action      string `json:"action"`
	GRPCAddress string `json:"grpcAddress,omitempty"`
	BearerToken string `json:"bearerToken,omitempty"`
	URL         string `json:"url,omitempty"`
	EntryID     string `json:"entryId,omitempty"`
}

type Response struct {
	Success    bool        `json:"success"`
	Error      string      `json:"error,omitempty"`
	Status     *Status     `json:"status,omitempty"`
	Matches    []Match     `json:"matches,omitempty"`
	Credential *Credential `json:"credential,omitempty"`
	Version    string      `json:"version,omitempty"`
}

type Status struct {
	Connected   bool   `json:"connected"`
	Locked      bool   `json:"locked"`
	Dirty       bool   `json:"dirty,omitempty"`
	EntryCount  uint32 `json:"entryCount,omitempty"`
	GRPCAddress string `json:"grpcAddress,omitempty"`
}

type Match struct {
	ID       string   `json:"id"`
	Title    string   `json:"title"`
	Username string   `json:"username,omitempty"`
	URL      string   `json:"url,omitempty"`
	Path     []string `json:"path,omitempty"`
	Quality  string   `json:"quality,omitempty"`
}

type Credential struct {
	ID       string `json:"id"`
	Username string `json:"username,omitempty"`
	Password string `json:"password,omitempty"`
	URL      string `json:"url,omitempty"`
}

type Connection struct {
	GRPCAddress string
	BearerToken string
}

type Client interface {
	Status(context.Context) (*keepassgov1.GetSessionStatusResponse, error)
	FindBrowserLogins(context.Context, string) ([]*keepassgov1.BrowserLoginMatch, error)
	GetBrowserCredential(context.Context, string, string) (*keepassgov1.GetBrowserCredentialResponse, error)
}

type Browser string

const (
	BrowserFirefox  Browser = "firefox"
	BrowserChrome   Browser = "chrome"
	BrowserChromium Browser = "chromium"
)

type NativeHostManifest struct {
	Name              string   `json:"name"`
	Description       string   `json:"description"`
	Path              string   `json:"path"`
	Type              string   `json:"type"`
	AllowedExtensions []string `json:"allowed_extensions,omitempty"`
	AllowedOrigins    []string `json:"allowed_origins,omitempty"`
}

func DefaultFirefoxExtensionID() string {
	return defaultFirefoxID
}

func ReadRequest(r io.Reader) (Request, error) {
	var sizeBuf [4]byte
	if _, err := io.ReadFull(r, sizeBuf[:]); err != nil {
		return Request{}, err
	}
	size := binary.LittleEndian.Uint32(sizeBuf[:])
	if size == 0 || size > maxNativeMessageSize {
		return Request{}, fmt.Errorf("invalid native message size %d", size)
	}
	body := make([]byte, size)
	if _, err := io.ReadFull(r, body); err != nil {
		return Request{}, err
	}
	var req Request
	if err := json.Unmarshal(body, &req); err != nil {
		return Request{}, fmt.Errorf("decode native request: %w", err)
	}
	return req, nil
}

func WriteResponse(w io.Writer, resp Response) error {
	data, err := json.Marshal(resp)
	if err != nil {
		return fmt.Errorf("encode native response: %w", err)
	}
	if len(data) > maxNativeMessageSize {
		return fmt.Errorf("native response too large: %d", len(data))
	}
	var sizeBuf [4]byte
	binary.LittleEndian.PutUint32(sizeBuf[:], uint32(len(data)))
	if _, err := w.Write(sizeBuf[:]); err != nil {
		return err
	}
	_, err = w.Write(data)
	return err
}

func (r Request) Connection() (Connection, error) {
	conn := Connection{
		GRPCAddress: strings.TrimSpace(r.GRPCAddress),
		BearerToken: strings.TrimSpace(r.BearerToken),
	}
	if conn.GRPCAddress == "" {
		conn.GRPCAddress = grpcaddr.Default(runtime.GOOS)
	}
	if conn.BearerToken == "" {
		return Connection{}, fmt.Errorf("browser bridge bearer token is required")
	}
	return conn, nil
}

func HandleRequest(ctx context.Context, req Request, client Client) Response {
	conn, err := req.Connection()
	if err != nil {
		return Response{Success: false, Error: err.Error()}
	}
	action := strings.TrimSpace(req.Action)
	switch action {
	case "status":
		status, err := statusResponse(ctx, client, conn.GRPCAddress)
		if err != nil {
			return Response{Success: false, Error: err.Error(), Status: disconnectedStatus(conn.GRPCAddress)}
		}
		return Response{Success: true, Status: status, Version: "1"}
	case "find-logins":
		status, err := statusResponse(ctx, client, conn.GRPCAddress)
		if err != nil {
			return Response{Success: false, Error: err.Error(), Status: disconnectedStatus(conn.GRPCAddress)}
		}
		if status.Locked {
			return Response{Success: true, Status: status, Matches: nil, Version: "1"}
		}
		matches, err := findMatches(ctx, client, req.URL)
		if err != nil {
			return Response{Success: false, Error: err.Error(), Status: status}
		}
		return Response{Success: true, Status: status, Matches: matches, Version: "1"}
	case "get-login":
		status, err := statusResponse(ctx, client, conn.GRPCAddress)
		if err != nil {
			return Response{Success: false, Error: err.Error(), Status: disconnectedStatus(conn.GRPCAddress)}
		}
		if status.Locked {
			return Response{Success: false, Error: "vault is locked", Status: status}
		}
		credential, err := loadCredential(ctx, client, req.EntryID, req.URL)
		if err != nil {
			return Response{Success: false, Error: err.Error(), Status: status}
		}
		return Response{Success: true, Status: status, Credential: credential, Version: "1"}
	default:
		return Response{Success: false, Error: fmt.Sprintf("unsupported action %q", action)}
	}
}

func disconnectedStatus(addr string) *Status {
	return &Status{Connected: false, GRPCAddress: strings.TrimSpace(addr)}
}

func statusResponse(ctx context.Context, client Client, addr string) (*Status, error) {
	resp, err := client.Status(ctx)
	if err != nil {
		return nil, err
	}
	return &Status{
		Connected:   true,
		Locked:      resp.GetLocked(),
		Dirty:       resp.GetDirty(),
		EntryCount:  resp.GetEntryCount(),
		GRPCAddress: strings.TrimSpace(addr),
	}, nil
}

func findMatches(ctx context.Context, client Client, rawURL string) ([]Match, error) {
	resp, err := client.FindBrowserLogins(ctx, strings.TrimSpace(rawURL))
	if err != nil {
		return nil, err
	}
	out := make([]Match, 0, len(resp))
	for _, match := range resp {
		out = append(out, Match{
			ID:       match.GetId(),
			Title:    match.GetTitle(),
			Username: match.GetUsername(),
			URL:      match.GetUrl(),
			Path:     append([]string(nil), match.GetPath()...),
			Quality:  match.GetQuality(),
		})
	}
	return out, nil
}

func loadCredential(ctx context.Context, client Client, entryID, rawURL string) (*Credential, error) {
	id := strings.TrimSpace(entryID)
	if id == "" {
		return nil, fmt.Errorf("entry id is required")
	}
	resp, err := client.GetBrowserCredential(ctx, id, strings.TrimSpace(rawURL))
	if err != nil {
		return nil, err
	}
	return &Credential{
		ID:       resp.GetId(),
		Username: resp.GetUsername(),
		Password: resp.GetPassword(),
		URL:      resp.GetUrl(),
	}, nil
}

func Manifest(browser Browser, binaryPath, extensionID string) (NativeHostManifest, error) {
	path := strings.TrimSpace(binaryPath)
	if path == "" {
		return NativeHostManifest{}, fmt.Errorf("native host binary path is required")
	}
	switch browser {
	case BrowserFirefox:
		id := strings.TrimSpace(extensionID)
		if id == "" {
			id = defaultFirefoxID
		}
		return NativeHostManifest{
			Name:              NativeHostName,
			Description:       "KeePassGO browser bridge",
			Path:              path,
			Type:              "stdio",
			AllowedExtensions: []string{id},
		}, nil
	case BrowserChrome, BrowserChromium:
		id := strings.TrimSpace(extensionID)
		if id == "" {
			return NativeHostManifest{}, fmt.Errorf("%s extension id is required", browser)
		}
		return NativeHostManifest{
			Name:           NativeHostName,
			Description:    "KeePassGO browser bridge",
			Path:           path,
			Type:           "stdio",
			AllowedOrigins: []string{"chrome-extension://" + id + "/"},
		}, nil
	default:
		return NativeHostManifest{}, fmt.Errorf("unsupported browser %q", browser)
	}
}

func ChromiumExtensionIDFromManifestKey(raw string) (string, error) {
	normalized := strings.TrimSpace(raw)
	normalized = strings.ReplaceAll(normalized, "-----BEGIN PUBLIC KEY-----", "")
	normalized = strings.ReplaceAll(normalized, "-----END PUBLIC KEY-----", "")
	normalized = strings.ReplaceAll(normalized, "\n", "")
	normalized = strings.ReplaceAll(normalized, "\r", "")
	normalized = strings.ReplaceAll(normalized, "\t", "")
	normalized = strings.ReplaceAll(normalized, " ", "")
	if normalized == "" {
		return "", fmt.Errorf("chromium extension key is required")
	}
	publicKeyDER, err := base64.StdEncoding.DecodeString(normalized)
	if err != nil {
		return "", fmt.Errorf("decode chromium extension key: %w", err)
	}
	hash := sha256.Sum256(publicKeyDER)
	var builder strings.Builder
	builder.Grow(chromiumIDBytes * 2)
	for _, b := range hash[:chromiumIDBytes] {
		builder.WriteByte('a' + ((b >> 4) & 0x0f))
		builder.WriteByte('a' + (b & 0x0f))
	}
	return builder.String(), nil
}

func DefaultManifestPath(browser Browser) (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	switch browser {
	case BrowserFirefox:
		return filepath.Join(home, ".mozilla", "native-messaging-hosts", NativeHostName+".json"), nil
	case BrowserChrome:
		return filepath.Join(home, ".config", "google-chrome", "NativeMessagingHosts", NativeHostName+".json"), nil
	case BrowserChromium:
		return filepath.Join(home, ".config", "chromium", "NativeMessagingHosts", NativeHostName+".json"), nil
	default:
		return "", fmt.Errorf("unsupported browser %q", browser)
	}
}

func InstallManifest(browser Browser, binaryPath, extensionID, outputPath string) (string, error) {
	manifest, err := Manifest(browser, binaryPath, extensionID)
	if err != nil {
		return "", err
	}
	path := strings.TrimSpace(outputPath)
	if path == "" {
		path, err = DefaultManifestPath(browser)
		if err != nil {
			return "", err
		}
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return "", fmt.Errorf("create native host manifest dir: %w", err)
	}
	data, err := json.MarshalIndent(manifest, "", "  ")
	if err != nil {
		return "", fmt.Errorf("encode native host manifest: %w", err)
	}
	data = append(data, '\n')
	if err := os.WriteFile(path, data, 0o644); err != nil {
		return "", fmt.Errorf("write native host manifest: %w", err)
	}
	return path, nil
}