package hostagent

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"mime/multipart"
	"net/http"
	"net/url"
	"time"

	"connectrpc.com/connect"

	pb "git.omukk.dev/wrenn/sandbox/proto/hostagent/gen"
	"git.omukk.dev/wrenn/sandbox/proto/hostagent/gen/hostagentv1connect"

	"git.omukk.dev/wrenn/sandbox/internal/sandbox"
)

// Server implements the HostAgentService Connect RPC handler.
type Server struct {
	hostagentv1connect.UnimplementedHostAgentServiceHandler
	mgr *sandbox.Manager
}

// NewServer creates a new host agent RPC server.
func NewServer(mgr *sandbox.Manager) *Server {
	return &Server{mgr: mgr}
}

func (s *Server) CreateSandbox(
	ctx context.Context,
	req *connect.Request[pb.CreateSandboxRequest],
) (*connect.Response[pb.CreateSandboxResponse], error) {
	msg := req.Msg

	sb, err := s.mgr.Create(ctx, msg.SandboxId, msg.Template, int(msg.Vcpus), int(msg.MemoryMb), int(msg.TimeoutSec))
	if err != nil {
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("create sandbox: %w", err))
	}

	return connect.NewResponse(&pb.CreateSandboxResponse{
		SandboxId: sb.ID,
		Status:    string(sb.Status),
		HostIp:    sb.HostIP.String(),
	}), nil
}

func (s *Server) DestroySandbox(
	ctx context.Context,
	req *connect.Request[pb.DestroySandboxRequest],
) (*connect.Response[pb.DestroySandboxResponse], error) {
	if err := s.mgr.Destroy(ctx, req.Msg.SandboxId); err != nil {
		return nil, connect.NewError(connect.CodeNotFound, err)
	}
	return connect.NewResponse(&pb.DestroySandboxResponse{}), nil
}

func (s *Server) PauseSandbox(
	ctx context.Context,
	req *connect.Request[pb.PauseSandboxRequest],
) (*connect.Response[pb.PauseSandboxResponse], error) {
	if err := s.mgr.Pause(ctx, req.Msg.SandboxId); err != nil {
		return nil, connect.NewError(connect.CodeInternal, err)
	}
	return connect.NewResponse(&pb.PauseSandboxResponse{}), nil
}

func (s *Server) ResumeSandbox(
	ctx context.Context,
	req *connect.Request[pb.ResumeSandboxRequest],
) (*connect.Response[pb.ResumeSandboxResponse], error) {
	if err := s.mgr.Resume(ctx, req.Msg.SandboxId); err != nil {
		return nil, connect.NewError(connect.CodeInternal, err)
	}
	return connect.NewResponse(&pb.ResumeSandboxResponse{}), nil
}

func (s *Server) Exec(
	ctx context.Context,
	req *connect.Request[pb.ExecRequest],
) (*connect.Response[pb.ExecResponse], error) {
	msg := req.Msg

	timeout := 30 * time.Second
	if msg.TimeoutSec > 0 {
		timeout = time.Duration(msg.TimeoutSec) * time.Second
	}

	execCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	result, err := s.mgr.Exec(execCtx, msg.SandboxId, msg.Cmd, msg.Args...)
	if err != nil {
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("exec: %w", err))
	}

	return connect.NewResponse(&pb.ExecResponse{
		Stdout:   result.Stdout,
		Stderr:   result.Stderr,
		ExitCode: result.ExitCode,
	}), nil
}

func (s *Server) WriteFile(
	ctx context.Context,
	req *connect.Request[pb.WriteFileRequest],
) (*connect.Response[pb.WriteFileResponse], error) {
	msg := req.Msg

	client, err := s.mgr.GetClient(msg.SandboxId)
	if err != nil {
		return nil, connect.NewError(connect.CodeNotFound, err)
	}

	if err := client.WriteFile(ctx, msg.Path, msg.Content); err != nil {
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("write file: %w", err))
	}

	return connect.NewResponse(&pb.WriteFileResponse{}), nil
}

func (s *Server) ReadFile(
	ctx context.Context,
	req *connect.Request[pb.ReadFileRequest],
) (*connect.Response[pb.ReadFileResponse], error) {
	msg := req.Msg

	client, err := s.mgr.GetClient(msg.SandboxId)
	if err != nil {
		return nil, connect.NewError(connect.CodeNotFound, err)
	}

	content, err := client.ReadFile(ctx, msg.Path)
	if err != nil {
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("read file: %w", err))
	}

	return connect.NewResponse(&pb.ReadFileResponse{Content: content}), nil
}

func (s *Server) ExecStream(
	ctx context.Context,
	req *connect.Request[pb.ExecStreamRequest],
	stream *connect.ServerStream[pb.ExecStreamResponse],
) error {
	msg := req.Msg

	// Only apply a timeout if explicitly requested; streaming execs may be long-running.
	execCtx := ctx
	if msg.TimeoutSec > 0 {
		var cancel context.CancelFunc
		execCtx, cancel = context.WithTimeout(ctx, time.Duration(msg.TimeoutSec)*time.Second)
		defer cancel()
	}

	events, err := s.mgr.ExecStream(execCtx, msg.SandboxId, msg.Cmd, msg.Args...)
	if err != nil {
		return connect.NewError(connect.CodeInternal, fmt.Errorf("exec stream: %w", err))
	}

	for ev := range events {
		var resp pb.ExecStreamResponse
		switch ev.Type {
		case "start":
			resp.Event = &pb.ExecStreamResponse_Start{
				Start: &pb.ExecStreamStart{Pid: ev.PID},
			}
		case "stdout":
			resp.Event = &pb.ExecStreamResponse_Data{
				Data: &pb.ExecStreamData{
					Output: &pb.ExecStreamData_Stdout{Stdout: ev.Data},
				},
			}
		case "stderr":
			resp.Event = &pb.ExecStreamResponse_Data{
				Data: &pb.ExecStreamData{
					Output: &pb.ExecStreamData_Stderr{Stderr: ev.Data},
				},
			}
		case "end":
			resp.Event = &pb.ExecStreamResponse_End{
				End: &pb.ExecStreamEnd{
					ExitCode: ev.ExitCode,
					Error:    ev.Error,
				},
			}
		}
		if err := stream.Send(&resp); err != nil {
			return err
		}
	}

	return nil
}

func (s *Server) WriteFileStream(
	ctx context.Context,
	stream *connect.ClientStream[pb.WriteFileStreamRequest],
) (*connect.Response[pb.WriteFileStreamResponse], error) {
	// First message must contain metadata.
	if !stream.Receive() {
		if err := stream.Err(); err != nil {
			return nil, connect.NewError(connect.CodeInternal, err)
		}
		return nil, connect.NewError(connect.CodeInvalidArgument, fmt.Errorf("empty stream"))
	}

	first := stream.Msg()
	meta := first.GetMeta()
	if meta == nil {
		return nil, connect.NewError(connect.CodeInvalidArgument, fmt.Errorf("first message must contain metadata"))
	}

	client, err := s.mgr.GetClient(meta.SandboxId)
	if err != nil {
		return nil, connect.NewError(connect.CodeNotFound, err)
	}

	// Use io.Pipe to stream chunks into a multipart body for envd's REST endpoint.
	pr, pw := io.Pipe()
	mpWriter := multipart.NewWriter(pw)

	// Write multipart data in a goroutine.
	errCh := make(chan error, 1)
	go func() {
		defer pw.Close()
		part, err := mpWriter.CreateFormFile("file", "upload")
		if err != nil {
			errCh <- fmt.Errorf("create multipart: %w", err)
			return
		}

		for stream.Receive() {
			chunk := stream.Msg().GetChunk()
			if len(chunk) == 0 {
				continue
			}
			if _, err := part.Write(chunk); err != nil {
				errCh <- fmt.Errorf("write chunk: %w", err)
				return
			}
		}
		if err := stream.Err(); err != nil {
			errCh <- err
			return
		}
		mpWriter.Close()
		errCh <- nil
	}()

	// Send the streaming multipart body to envd.
	base := client.BaseURL()
	u := fmt.Sprintf("%s/files?%s", base, url.Values{
		"path":     {meta.Path},
		"username": {"root"},
	}.Encode())

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, u, pr)
	if err != nil {
		pw.CloseWithError(err)
		<-errCh
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("create request: %w", err))
	}
	httpReq.Header.Set("Content-Type", mpWriter.FormDataContentType())

	resp, err := http.DefaultClient.Do(httpReq)
	if err != nil {
		pw.CloseWithError(err)
		<-errCh
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("write file stream: %w", err))
	}
	defer resp.Body.Close()

	// Wait for the writer goroutine.
	if writerErr := <-errCh; writerErr != nil {
		return nil, connect.NewError(connect.CodeInternal, writerErr)
	}

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNoContent {
		body, _ := io.ReadAll(resp.Body)
		return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("envd write: status %d: %s", resp.StatusCode, string(body)))
	}

	slog.Debug("streaming file write complete", "sandbox_id", meta.SandboxId, "path", meta.Path)
	return connect.NewResponse(&pb.WriteFileStreamResponse{}), nil
}

func (s *Server) ReadFileStream(
	ctx context.Context,
	req *connect.Request[pb.ReadFileStreamRequest],
	stream *connect.ServerStream[pb.ReadFileStreamResponse],
) error {
	msg := req.Msg

	client, err := s.mgr.GetClient(msg.SandboxId)
	if err != nil {
		return connect.NewError(connect.CodeNotFound, err)
	}

	base := client.BaseURL()
	u := fmt.Sprintf("%s/files?%s", base, url.Values{
		"path":     {msg.Path},
		"username": {"root"},
	}.Encode())

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return connect.NewError(connect.CodeInternal, fmt.Errorf("create request: %w", err))
	}

	resp, err := http.DefaultClient.Do(httpReq)
	if err != nil {
		return connect.NewError(connect.CodeInternal, fmt.Errorf("read file stream: %w", err))
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return connect.NewError(connect.CodeInternal, fmt.Errorf("envd read: status %d: %s", resp.StatusCode, string(body)))
	}

	// Stream file content in 64KB chunks.
	buf := make([]byte, 64*1024)
	for {
		n, err := resp.Body.Read(buf)
		if n > 0 {
			chunk := make([]byte, n)
			copy(chunk, buf[:n])
			if sendErr := stream.Send(&pb.ReadFileStreamResponse{Chunk: chunk}); sendErr != nil {
				return sendErr
			}
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			return connect.NewError(connect.CodeInternal, fmt.Errorf("read body: %w", err))
		}
	}

	return nil
}

func (s *Server) ListSandboxes(
	ctx context.Context,
	req *connect.Request[pb.ListSandboxesRequest],
) (*connect.Response[pb.ListSandboxesResponse], error) {
	sandboxes := s.mgr.List()

	infos := make([]*pb.SandboxInfo, len(sandboxes))
	for i, sb := range sandboxes {
		infos[i] = &pb.SandboxInfo{
			SandboxId:       sb.ID,
			Status:          string(sb.Status),
			Template:        sb.Template,
			Vcpus:           int32(sb.VCPUs),
			MemoryMb:        int32(sb.MemoryMB),
			HostIp:          sb.HostIP.String(),
			CreatedAtUnix:   sb.CreatedAt.Unix(),
			LastActiveAtUnix: sb.LastActiveAt.Unix(),
			TimeoutSec:      int32(sb.TimeoutSec),
		}
	}

	return connect.NewResponse(&pb.ListSandboxesResponse{
		Sandboxes: infos,
	}), nil
}