package dist

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"

	"go.uber.org/zap"

	"gitlab.com/slon/shad-go/distbuild/pkg/api"
	"gitlab.com/slon/shad-go/distbuild/pkg/build"
	"gitlab.com/slon/shad-go/distbuild/pkg/filecache"
	"gitlab.com/slon/shad-go/distbuild/pkg/scheduler"
)

type Coordinator struct {
	log       *zap.Logger
	mux       *http.ServeMux
	fileCache *filecache.Cache

	mu        sync.Mutex
	builds    map[build.ID]*Build
	scheduler *scheduler.Scheduler
}

var defaultConfig = scheduler.Config{
	CacheTimeout: time.Millisecond * 10,
	DepsTimeout:  time.Millisecond * 100,
}

func NewCoordinator(
	log *zap.Logger,
	fileCache *filecache.Cache,
) *Coordinator {
	c := &Coordinator{
		log:       log,
		mux:       http.NewServeMux(),
		fileCache: fileCache,

		builds:    make(map[build.ID]*Build),
		scheduler: scheduler.NewScheduler(log, defaultConfig),
	}

	apiHandler := api.NewServiceHandler(log, c)
	apiHandler.Register(c.mux)

	c.mux.HandleFunc("/heartbeat", c.Heartbeat)
	return c
}

func (c *Coordinator) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	c.mux.ServeHTTP(w, r)
}

func (c *Coordinator) StartBuild(ctx context.Context, req *api.BuildRequest, w api.StatusWriter) error {
	if err := w.Started(&api.BuildStarted{}); err != nil {
		return err
	}

	for _, job := range req.Graph.Jobs {
		job := job

		s := c.scheduler.ScheduleJob(&job)

		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-s.Finished:
		}

		c.log.Debug("job finished", zap.String("job_id", job.ID.String()))

		jobFinished := api.StatusUpdate{JobFinished: s.Result}
		if err := w.Updated(&jobFinished); err != nil {
			return err
		}
	}

	finished := api.StatusUpdate{BuildFinished: &api.BuildFinished{}}
	return w.Updated(&finished)
}

func (c *Coordinator) SignalBuild(ctx context.Context, buildID build.ID, signal *api.SignalRequest) (*api.SignalResponse, error) {
	panic("implement me")
}

func (c *Coordinator) doHeartbeat(w http.ResponseWriter, r *http.Request) error {
	var req api.HeartbeatRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		return fmt.Errorf("invalid request: %w", err)
	}

	c.scheduler.RegisterWorker(req.WorkerID)

	for _, job := range req.FinishedJob {
		job := job

		c.scheduler.OnJobComplete(req.WorkerID, job.ID, &job)
	}

	rsp := api.HeartbeatResponse{
		JobsToRun: map[build.ID]api.JobSpec{},
	}

	job := c.scheduler.PickJob(req.WorkerID, r.Context().Done())
	if job != nil {
		rsp.JobsToRun[job.Job.ID] = api.JobSpec{Job: *job.Job}
	}

	if err := json.NewEncoder(w).Encode(rsp); err != nil {
		return err
	}

	return nil
}

func (c *Coordinator) Heartbeat(w http.ResponseWriter, r *http.Request) {
	c.log.Debug("heartbeat started")
	if err := c.doHeartbeat(w, r); err != nil {
		c.log.Error("heartbeat failed", zap.Error(err))

		w.WriteHeader(http.StatusBadRequest)
		_, _ = w.Write([]byte(err.Error()))
		return
	}
	c.log.Debug("heartbeat finished")
}