package beads

import (
	"bufio"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"path/filepath"
	"time"
)

// MaxUnixSocketPath is the maximum length for Unix socket paths.
const MaxUnixSocketPath = 103

// rpcClient represents an RPC client for the bd daemon.
type rpcClient struct {
	conn       net.Conn
	socketPath string
	timeout    time.Duration
	cwd        string
}

// rpcRequest represents an RPC request to the daemon.
type rpcRequest struct {
	Operation string          `json:"operation"`
	Args      json.RawMessage `json:"args"`
	Cwd       string          `json:"cwd,omitempty"`
}

// rpcResponse represents an RPC response from the daemon.
type rpcResponse struct {
	Success bool            `json:"success"`
	Data    json.RawMessage `json:"data,omitempty"`
	Error   string          `json:"error,omitempty"`
}

// tryConnectRPC attempts to connect to the bd daemon.
// Returns nil if no daemon is running.
func tryConnectRPC(workspacePath string) *rpcClient {
	socketPath := socketPathForWorkspace(workspacePath)

	// Check if socket exists
	if _, err := os.Stat(socketPath); os.IsNotExist(err) {
		return nil
	}

	conn, err := net.DialTimeout("unix", socketPath, 200*time.Millisecond)
	if err != nil {
		return nil
	}

	client := &rpcClient{
		conn:       conn,
		socketPath: socketPath,
		timeout:    30 * time.Second,
		cwd:        workspacePath,
	}

	// Quick health check
	if err := client.ping(); err != nil {
		_ = conn.Close()
		return nil
	}

	return client
}

// close closes the RPC connection.
func (c *rpcClient) close() error {
	if c.conn != nil {
		return c.conn.Close()
	}
	return nil
}

// execute sends a request and returns the response.
func (c *rpcClient) execute(operation string, args interface{}) (*rpcResponse, error) {
	argsJSON, err := json.Marshal(args)
	if err != nil {
		return nil, fmt.Errorf("marshaling args: %w", err)
	}

	req := rpcRequest{
		Operation: operation,
		Args:      argsJSON,
		Cwd:       c.cwd,
	}

	reqJSON, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshaling request: %w", err)
	}

	if c.timeout > 0 {
		deadline := time.Now().Add(c.timeout)
		if err := c.conn.SetDeadline(deadline); err != nil {
			return nil, fmt.Errorf("setting deadline: %w", err)
		}
	}

	writer := bufio.NewWriter(c.conn)
	if _, err := writer.Write(reqJSON); err != nil {
		return nil, fmt.Errorf("writing request: %w", err)
	}
	if err := writer.WriteByte('\n'); err != nil {
		return nil, fmt.Errorf("writing newline: %w", err)
	}
	if err := writer.Flush(); err != nil {
		return nil, fmt.Errorf("flushing: %w", err)
	}

	reader := bufio.NewReader(c.conn)
	respLine, err := reader.ReadBytes('\n')
	if err != nil {
		return nil, fmt.Errorf("reading response: %w", err)
	}

	var resp rpcResponse
	if err := json.Unmarshal(respLine, &resp); err != nil {
		return nil, fmt.Errorf("unmarshaling response: %w", err)
	}

	if !resp.Success {
		return &resp, fmt.Errorf("operation failed: %s", resp.Error)
	}

	return &resp, nil
}

// ping verifies the daemon is alive.
func (c *rpcClient) ping() error {
	_, err := c.execute("ping", nil)
	return err
}

// socketPathForWorkspace returns the socket path for a workspace.
// This mirrors the logic in beads/internal/rpc/socket_path.go.
func socketPathForWorkspace(workspacePath string) string {
	// Compute the "natural" socket path in .beads/
	naturalPath := filepath.Join(workspacePath, ".beads", "bd.sock")

	// If natural path is short enough, use it
	if len(naturalPath) <= MaxUnixSocketPath {
		return naturalPath
	}

	// Path too long - use /tmp with hash
	hash := sha256.Sum256([]byte(workspacePath))
	hashStr := hex.EncodeToString(hash[:4])
	return filepath.Join("/tmp", "beads-"+hashStr, "bd.sock")
}

// getRPCClient returns the RPC client, initializing on first call.
// Returns nil if daemon is not available.
func (b *Beads) getRPCClient() *rpcClient {
	if b.rpcChecked {
		return b.rpcClient
	}

	b.rpcChecked = true

	// Don't use RPC in isolated mode (tests)
	if b.isolated {
		return nil
	}

	// Resolve workspace path for socket discovery
	workspacePath := b.beadsDir
	if workspacePath == "" {
		workspacePath = ResolveBeadsDir(b.workDir)
	}

	// Get the workspace root (parent of .beads)
	if filepath.Base(workspacePath) == ".beads" {
		workspacePath = filepath.Dir(workspacePath)
	}

	b.rpcClient = tryConnectRPC(workspacePath)
	b.rpcAvailable = b.rpcClient != nil
	return b.rpcClient
}

// closeRPC closes the RPC client if connected.
func (b *Beads) closeRPC() {
	if b.rpcClient != nil {
		_ = b.rpcClient.close()
		b.rpcClient = nil
	}
}

// RPC operation argument types

type rpcListArgs struct {
	Status        string   `json:"status,omitempty"`
	Assignee      string   `json:"assignee,omitempty"`
	Labels        []string `json:"labels,omitempty"`
	LabelsAny     []string `json:"labels_any,omitempty"`
	ExcludeStatus []string `json:"exclude_status,omitempty"`
	Priority      *int     `json:"priority,omitempty"`
	ParentID      string   `json:"parent_id,omitempty"`
	NoAssignee    bool     `json:"no_assignee,omitempty"`
	Limit         int      `json:"limit,omitempty"`
}

type rpcShowArgs struct {
	ID string `json:"id"`
}

type rpcUpdateArgs struct {
	ID           string   `json:"id"`
	Title        *string  `json:"title,omitempty"`
	Status       *string  `json:"status,omitempty"`
	Priority     *int     `json:"priority,omitempty"`
	Description  *string  `json:"description,omitempty"`
	Assignee     *string  `json:"assignee,omitempty"`
	AddLabels    []string `json:"add_labels,omitempty"`
	RemoveLabels []string `json:"remove_labels,omitempty"`
	SetLabels    []string `json:"set_labels,omitempty"`
}

type rpcCloseArgs struct {
	ID      string `json:"id"`
	Reason  string `json:"reason,omitempty"`
	Session string `json:"session,omitempty"`
	Force   bool   `json:"force,omitempty"`
}

// listViaRPC performs a list operation via the daemon RPC.
func (b *Beads) listViaRPC(opts ListOptions) ([]*Issue, error) {
	client := b.getRPCClient()
	if client == nil {
		return nil, fmt.Errorf("no RPC client")
	}

	args := rpcListArgs{
		Status:   opts.Status,
		Assignee: opts.Assignee,
		ParentID: opts.Parent,
	}

	// Convert Label to Labels array if set
	if opts.Label != "" {
		args.Labels = []string{opts.Label}
	}

	// Handle priority: -1 means no filter
	if opts.Priority >= 0 {
		args.Priority = &opts.Priority
	}

	if opts.NoAssignee {
		args.NoAssignee = true
	}

	resp, err := client.execute("list", args)
	if err != nil {
		return nil, err
	}

	var issues []*Issue
	if err := json.Unmarshal(resp.Data, &issues); err != nil {
		return nil, fmt.Errorf("unmarshaling issues: %w", err)
	}

	return issues, nil
}

// showViaRPC performs a show operation via the daemon RPC.
func (b *Beads) showViaRPC(id string) (*Issue, error) {
	client := b.getRPCClient()
	if client == nil {
		return nil, fmt.Errorf("no RPC client")
	}

	resp, err := client.execute("show", rpcShowArgs{ID: id})
	if err != nil {
		return nil, err
	}

	var issue Issue
	if err := json.Unmarshal(resp.Data, &issue); err != nil {
		return nil, fmt.Errorf("unmarshaling issue: %w", err)
	}

	return &issue, nil
}

// updateViaRPC performs an update operation via the daemon RPC.
func (b *Beads) updateViaRPC(id string, opts UpdateOptions) error {
	client := b.getRPCClient()
	if client == nil {
		return fmt.Errorf("no RPC client")
	}

	args := rpcUpdateArgs{
		ID:           id,
		Title:        opts.Title,
		Status:       opts.Status,
		Priority:     opts.Priority,
		Description:  opts.Description,
		Assignee:     opts.Assignee,
		AddLabels:    opts.AddLabels,
		RemoveLabels: opts.RemoveLabels,
		SetLabels:    opts.SetLabels,
	}

	_, err := client.execute("update", args)
	return err
}

// closeViaRPC performs a close operation via the daemon RPC.
func (b *Beads) closeViaRPC(id, reason, session string, force bool) error {
	client := b.getRPCClient()
	if client == nil {
		return fmt.Errorf("no RPC client")
	}

	args := rpcCloseArgs{
		ID:      id,
		Reason:  reason,
		Session: session,
		Force:   force,
	}

	_, err := client.execute("close", args)
	return err
}