package api

import (
	"bufio"
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/ClusterCockpit/cc-backend/internal/auth"
	"github.com/ClusterCockpit/cc-backend/internal/config"
	"github.com/ClusterCockpit/cc-backend/internal/graph"
	"github.com/ClusterCockpit/cc-backend/internal/graph/model"
	"github.com/ClusterCockpit/cc-backend/internal/metricdata"
	"github.com/ClusterCockpit/cc-backend/internal/repository"
	"github.com/ClusterCockpit/cc-backend/pkg/log"
	"github.com/ClusterCockpit/cc-backend/pkg/schema"
	"github.com/gorilla/mux"
)

type RestApi struct {
	JobRepository     *repository.JobRepository
	Resolver          *graph.Resolver
	Authentication    *auth.Authentication
	MachineStateDir   string
	OngoingArchivings sync.WaitGroup
}

func (api *RestApi) MountRoutes(r *mux.Router) {
	r = r.PathPrefix("/api").Subrouter()
	r.StrictSlash(true)

	r.HandleFunc("/jobs/start_job/", api.startJob).Methods(http.MethodPost, http.MethodPut)
	r.HandleFunc("/jobs/stop_job/", api.stopJob).Methods(http.MethodPost, http.MethodPut)
	r.HandleFunc("/jobs/stop_job/{id}", api.stopJob).Methods(http.MethodPost, http.MethodPut)
	r.HandleFunc("/jobs/import/", api.importJob).Methods(http.MethodPost, http.MethodPut)

	r.HandleFunc("/jobs/", api.getJobs).Methods(http.MethodGet)
	// r.HandleFunc("/jobs/{id}", api.getJob).Methods(http.MethodGet)
	r.HandleFunc("/jobs/tag_job/{id}", api.tagJob).Methods(http.MethodPost, http.MethodPatch)

	r.HandleFunc("/jobs/metrics/{id}", api.getJobMetrics).Methods(http.MethodGet)

	if api.Authentication != nil {
		r.HandleFunc("/jwt/", api.getJWT).Methods(http.MethodGet)
		r.HandleFunc("/users/", api.createUser).Methods(http.MethodPost, http.MethodPut)
		r.HandleFunc("/users/", api.getUsers).Methods(http.MethodGet)
		r.HandleFunc("/users/", api.deleteUser).Methods(http.MethodDelete)
		r.HandleFunc("/user/{id}", api.updateUser).Methods(http.MethodPost)
		r.HandleFunc("/configuration/", api.updateConfiguration).Methods(http.MethodPost)
	}

	if api.MachineStateDir != "" {
		r.HandleFunc("/machine_state/{cluster}/{host}", api.getMachineState).Methods(http.MethodGet)
		r.HandleFunc("/machine_state/{cluster}/{host}", api.putMachineState).Methods(http.MethodPut, http.MethodPost)
	}
}

type StartJobApiResponse struct {
	DBID int64 `json:"id"`
}

type StopJobApiRequest struct {
	// JobId, ClusterId and StartTime are optional.
	// They are only used if no database id was provided.
	JobId     *int64  `json:"jobId"`
	Cluster   *string `json:"cluster"`
	StartTime *int64  `json:"startTime"`

	// Payload
	StopTime int64           `json:"stopTime"`
	State    schema.JobState `json:"jobState"`
}

type ErrorResponse struct {
	Status string `json:"status"`
	Error  string `json:"error"`
}

func handleError(err error, statusCode int, rw http.ResponseWriter) {
	log.Warnf("REST API: %s", err.Error())
	rw.Header().Add("Content-Type", "application/json")
	rw.WriteHeader(statusCode)
	json.NewEncoder(rw).Encode(ErrorResponse{
		Status: http.StatusText(statusCode),
		Error:  err.Error(),
	})
}

func decode(r io.Reader, val interface{}) error {
	dec := json.NewDecoder(r)
	dec.DisallowUnknownFields()
	return dec.Decode(val)
}

type TagJobApiRequest []*struct {
	Name string `json:"name"`
	Type string `json:"type"`
}

// Return a list of jobs
func (api *RestApi) getJobs(rw http.ResponseWriter, r *http.Request) {
	withMetadata := false
	filter := &model.JobFilter{}
	page := &model.PageRequest{ItemsPerPage: -1, Page: 1}
	order := &model.OrderByInput{Field: "startTime", Order: model.SortDirectionEnumDesc}
	for key, vals := range r.URL.Query() {
		switch key {
		case "state":
			for _, s := range vals {
				state := schema.JobState(s)
				if !state.Valid() {
					http.Error(rw, "invalid query parameter value: state", http.StatusBadRequest)
					return
				}
				filter.State = append(filter.State, state)
			}
		case "cluster":
			filter.Cluster = &model.StringInput{Eq: &vals[0]}
		case "start-time":
			st := strings.Split(vals[0], "-")
			if len(st) != 2 {
				http.Error(rw, "invalid query parameter value: startTime", http.StatusBadRequest)
				return
			}
			from, err := strconv.ParseInt(st[0], 10, 64)
			if err != nil {
				http.Error(rw, err.Error(), http.StatusBadRequest)
				return
			}
			to, err := strconv.ParseInt(st[1], 10, 64)
			if err != nil {
				http.Error(rw, err.Error(), http.StatusBadRequest)
				return
			}
			ufrom, uto := time.Unix(from, 0), time.Unix(to, 0)
			filter.StartTime = &model.TimeRange{From: &ufrom, To: &uto}
		case "page":
			x, err := strconv.Atoi(vals[0])
			if err != nil {
				http.Error(rw, err.Error(), http.StatusBadRequest)
				return
			}
			page.Page = x
		case "items-per-page":
			x, err := strconv.Atoi(vals[0])
			if err != nil {
				http.Error(rw, err.Error(), http.StatusBadRequest)
				return
			}
			page.ItemsPerPage = x
		case "with-metadata":
			withMetadata = true
		default:
			http.Error(rw, "invalid query parameter: "+key, http.StatusBadRequest)
			return
		}
	}

	jobs, err := api.JobRepository.QueryJobs(r.Context(), []*model.JobFilter{filter}, page, order)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	results := make([]*schema.JobMeta, 0, len(jobs))
	for _, job := range jobs {
		if withMetadata {
			if _, err := api.JobRepository.FetchMetadata(job); err != nil {
				http.Error(rw, err.Error(), http.StatusInternalServerError)
				return
			}
		}

		res := &schema.JobMeta{
			ID:        &job.ID,
			BaseJob:   job.BaseJob,
			StartTime: job.StartTime.Unix(),
		}

		res.Tags, err = api.JobRepository.GetTags(&job.ID)
		if err != nil {
			http.Error(rw, err.Error(), http.StatusInternalServerError)
			return
		}

		if res.MonitoringStatus == schema.MonitoringStatusArchivingSuccessful {
			res.Statistics, err = metricdata.GetStatistics(job)
			if err != nil {
				if err != nil {
					http.Error(rw, err.Error(), http.StatusInternalServerError)
					return
				}
			}
		}

		results = append(results, res)
	}

	log.Debugf("/api/jobs: %d jobs returned", len(results))
	bw := bufio.NewWriter(rw)
	defer bw.Flush()
	if err := json.NewEncoder(bw).Encode(map[string]interface{}{
		"jobs": results,
	}); err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}
}

// Add a tag to a job
func (api *RestApi) tagJob(rw http.ResponseWriter, r *http.Request) {
	iid, err := strconv.ParseInt(mux.Vars(r)["id"], 10, 64)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusBadRequest)
		return
	}

	job, err := api.JobRepository.FindById(iid)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusNotFound)
		return
	}

	job.Tags, err = api.JobRepository.GetTags(&job.ID)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	var req TagJobApiRequest
	if err := decode(r.Body, &req); err != nil {
		http.Error(rw, err.Error(), http.StatusBadRequest)
		return
	}

	for _, tag := range req {
		tagId, err := api.JobRepository.AddTagOrCreate(job.ID, tag.Type, tag.Name)
		if err != nil {
			http.Error(rw, err.Error(), http.StatusInternalServerError)
			return
		}

		job.Tags = append(job.Tags, &schema.Tag{
			ID:   tagId,
			Type: tag.Type,
			Name: tag.Name,
		})
	}

	rw.Header().Add("Content-Type", "application/json")
	rw.WriteHeader(http.StatusOK)
	json.NewEncoder(rw).Encode(job)
}

// A new job started. The body should be in the `meta.json` format, but some fields required
// there are optional here (e.g. `jobState` defaults to "running").
func (api *RestApi) startJob(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); user != nil && !user.HasRole(auth.RoleApi) {
		handleError(fmt.Errorf("missing role: %#v", auth.RoleApi), http.StatusForbidden, rw)
		return
	}

	req := schema.JobMeta{BaseJob: schema.JobDefaults}
	if err := decode(r.Body, &req); err != nil {
		handleError(fmt.Errorf("parsing request body failed: %w", err), http.StatusBadRequest, rw)
		return
	}

	if req.State == "" {
		req.State = schema.JobStateRunning
	}
	if err := repository.SanityChecks(&req.BaseJob); err != nil {
		handleError(err, http.StatusBadRequest, rw)
		return
	}

	// Check if combination of (job_id, cluster_id, start_time) already exists:
	job, err := api.JobRepository.Find(&req.JobID, &req.Cluster, nil)
	if err != nil && err != sql.ErrNoRows {
		handleError(fmt.Errorf("checking for duplicate failed: %w", err), http.StatusInternalServerError, rw)
		return
	} else if err == nil {
		if (req.StartTime - job.StartTimeUnix) < 86400 {
			handleError(fmt.Errorf("a job with that jobId, cluster and startTime already exists: dbid: %d", job.ID), http.StatusUnprocessableEntity, rw)
			return
		}
	}

	id, err := api.JobRepository.Start(&req)
	if err != nil {
		handleError(fmt.Errorf("insert into database failed: %w", err), http.StatusInternalServerError, rw)
		return
	}

	for _, tag := range req.Tags {
		if _, err := api.JobRepository.AddTagOrCreate(id, tag.Type, tag.Name); err != nil {
			http.Error(rw, err.Error(), http.StatusInternalServerError)
			handleError(fmt.Errorf("adding tag to new job %d failed: %w", id, err), http.StatusInternalServerError, rw)
			return
		}
	}

	log.Printf("new job (id: %d): cluster=%s, jobId=%d, user=%s, startTime=%d", id, req.Cluster, req.JobID, req.User, req.StartTime)
	rw.Header().Add("Content-Type", "application/json")
	rw.WriteHeader(http.StatusCreated)
	json.NewEncoder(rw).Encode(StartJobApiResponse{
		DBID: id,
	})
}

// A job has stopped and should be archived.
func (api *RestApi) stopJob(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); user != nil && !user.HasRole(auth.RoleApi) {
		handleError(fmt.Errorf("missing role: %#v", auth.RoleApi), http.StatusForbidden, rw)
		return
	}

	// Parse request body
	req := StopJobApiRequest{}
	if err := decode(r.Body, &req); err != nil {
		handleError(fmt.Errorf("parsing request body failed: %w", err), http.StatusBadRequest, rw)
		return
	}

	// Fetch job (that will be stopped) from db
	id, ok := mux.Vars(r)["id"]
	var job *schema.Job
	var err error
	if ok {
		id, e := strconv.ParseInt(id, 10, 64)
		if e != nil {
			handleError(fmt.Errorf("integer expected in path for id: %w", e), http.StatusBadRequest, rw)
			return
		}

		job, err = api.JobRepository.FindById(id)
	} else {
		if req.JobId == nil {
			handleError(errors.New("the field 'jobId' is required"), http.StatusBadRequest, rw)
			return
		}

		job, err = api.JobRepository.Find(req.JobId, req.Cluster, req.StartTime)
	}
	if err != nil {
		handleError(fmt.Errorf("finding job failed: %w", err), http.StatusUnprocessableEntity, rw)
		return
	}

	// Sanity checks
	if job == nil || job.StartTime.Unix() >= req.StopTime || job.State != schema.JobStateRunning {
		handleError(errors.New("stopTime must be larger than startTime and only running jobs can be stopped"), http.StatusBadRequest, rw)
		return
	}
	if req.State != "" && !req.State.Valid() {
		handleError(fmt.Errorf("invalid job state: %#v", req.State), http.StatusBadRequest, rw)
		return
	} else {
		req.State = schema.JobStateCompleted
	}

	// Mark job as stopped in the database (update state and duration)
	job.Duration = int32(req.StopTime - job.StartTime.Unix())
	job.State = req.State
	if err := api.JobRepository.Stop(job.ID, job.Duration, job.State, job.MonitoringStatus); err != nil {
		handleError(fmt.Errorf("marking job as stopped failed: %w", err), http.StatusInternalServerError, rw)
		return
	}

	log.Printf("archiving job... (dbid: %d): cluster=%s, jobId=%d, user=%s, startTime=%s", job.ID, job.Cluster, job.JobID, job.User, job.StartTime)

	// Send a response (with status OK). This means that erros that happen from here on forward
	// can *NOT* be communicated to the client. If reading from a MetricDataRepository or
	// writing to the filesystem fails, the client will not know.
	rw.Header().Add("Content-Type", "application/json")
	rw.WriteHeader(http.StatusOK)
	json.NewEncoder(rw).Encode(job)

	// Monitoring is disabled...
	if job.MonitoringStatus == schema.MonitoringStatusDisabled {
		return
	}

	// We need to start a new goroutine as this functions needs to return
	// for the response to be flushed to the client.
	api.OngoingArchivings.Add(1) // So that a shutdown does not interrupt this goroutine.
	go func() {
		defer api.OngoingArchivings.Done()

		if _, err := api.JobRepository.FetchMetadata(job); err != nil {
			log.Errorf("archiving job (dbid: %d) failed: %s", job.ID, err.Error())
			api.JobRepository.UpdateMonitoringStatus(job.ID, schema.MonitoringStatusArchivingFailed)
			return
		}

		// metricdata.ArchiveJob will fetch all the data from a MetricDataRepository and create meta.json/data.json files
		jobMeta, err := metricdata.ArchiveJob(job, context.Background())
		if err != nil {
			log.Errorf("archiving job (dbid: %d) failed: %s", job.ID, err.Error())
			api.JobRepository.UpdateMonitoringStatus(job.ID, schema.MonitoringStatusArchivingFailed)
			return
		}

		// Update the jobs database entry one last time:
		if err := api.JobRepository.Archive(job.ID, schema.MonitoringStatusArchivingSuccessful, jobMeta.Statistics); err != nil {
			log.Errorf("archiving job (dbid: %d) failed: %s", job.ID, err.Error())
			return
		}

		log.Printf("archiving job (dbid: %d) successful", job.ID)
	}()
}

func (api *RestApi) importJob(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); user != nil && !user.HasRole(auth.RoleApi) {
		handleError(fmt.Errorf("missing role: %#v", auth.RoleApi), http.StatusForbidden, rw)
		return
	}

	var body struct {
		Meta *schema.JobMeta `json:"meta"`
		Data *schema.JobData `json:"data"`
	}
	if err := decode(r.Body, &body); err != nil {
		handleError(fmt.Errorf("import failed: %s", err.Error()), http.StatusBadRequest, rw)
		return
	}

	if err := api.JobRepository.ImportJob(body.Meta, body.Data); err != nil {
		handleError(fmt.Errorf("import failed: %s", err.Error()), http.StatusUnprocessableEntity, rw)
		return
	}

	rw.Write([]byte(`{ "status": "OK" }`))
}

func (api *RestApi) getJobMetrics(rw http.ResponseWriter, r *http.Request) {
	id := mux.Vars(r)["id"]
	metrics := r.URL.Query()["metric"]
	var scopes []schema.MetricScope
	for _, scope := range r.URL.Query()["scope"] {
		var s schema.MetricScope
		if err := s.UnmarshalGQL(scope); err != nil {
			http.Error(rw, err.Error(), http.StatusBadRequest)
			return
		}
		scopes = append(scopes, s)
	}

	rw.Header().Add("Content-Type", "application/json")
	rw.WriteHeader(http.StatusOK)

	type Respone struct {
		Data *struct {
			JobMetrics []*model.JobMetricWithName `json:"jobMetrics"`
		} `json:"data"`
		Error *struct {
			Message string `json:"message"`
		} `json:"error"`
	}

	data, err := api.Resolver.Query().JobMetrics(r.Context(), id, metrics, scopes)
	if err != nil {
		json.NewEncoder(rw).Encode(Respone{
			Error: &struct {
				Message string "json:\"message\""
			}{Message: err.Error()},
		})
		return
	}

	json.NewEncoder(rw).Encode(Respone{
		Data: &struct {
			JobMetrics []*model.JobMetricWithName "json:\"jobMetrics\""
		}{JobMetrics: data},
	})
}

func (api *RestApi) getJWT(rw http.ResponseWriter, r *http.Request) {
	rw.Header().Set("Content-Type", "text/plain")
	username := r.FormValue("username")
	me := auth.GetUser(r.Context())
	if !me.HasRole(auth.RoleAdmin) {
		if username != me.Username {
			http.Error(rw, "only admins are allowed to sign JWTs not for themselves", http.StatusForbidden)
			return
		}
	}

	user, err := api.Authentication.GetUser(username)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	jwt, err := api.Authentication.JwtAuth.ProvideJWT(user)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	rw.WriteHeader(http.StatusOK)
	rw.Write([]byte(jwt))
}

func (api *RestApi) createUser(rw http.ResponseWriter, r *http.Request) {
	rw.Header().Set("Content-Type", "text/plain")
	me := auth.GetUser(r.Context())
	if !me.HasRole(auth.RoleAdmin) {
		http.Error(rw, "only admins are allowed to create new users", http.StatusForbidden)
		return
	}

	username, password, role, name, email := r.FormValue("username"), r.FormValue("password"), r.FormValue("role"), r.FormValue("name"), r.FormValue("email")
	if len(password) == 0 && role != auth.RoleApi {
		http.Error(rw, "only API users are allowed to have a blank password (login will be impossible)", http.StatusBadRequest)
		return
	}

	if err := api.Authentication.AddUser(&auth.User{
		Username: username,
		Name:     name,
		Password: password,
		Email:    email,
		Roles:    []string{role}}); err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	rw.Write([]byte(fmt.Sprintf("User %#v successfully created!\n", username)))
}

func (api *RestApi) deleteUser(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); !user.HasRole(auth.RoleAdmin) {
		http.Error(rw, "only admins are allowed to delete a user", http.StatusForbidden)
		return
	}

	username := r.FormValue("username")
	if err := api.Authentication.DelUser(username); err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	rw.WriteHeader(http.StatusOK)
}

func (api *RestApi) getUsers(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); !user.HasRole(auth.RoleAdmin) {
		http.Error(rw, "only admins are allowed to fetch a list of users", http.StatusForbidden)
		return
	}

	users, err := api.Authentication.ListUsers(r.URL.Query().Get("not-just-user") == "true")
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	json.NewEncoder(rw).Encode(users)
}

func (api *RestApi) updateUser(rw http.ResponseWriter, r *http.Request) {
	if user := auth.GetUser(r.Context()); !user.HasRole(auth.RoleAdmin) {
		http.Error(rw, "only admins are allowed to update a user", http.StatusForbidden)
		return
	}

	// TODO: Handle anything but roles...
	newrole := r.FormValue("add-role")
	if err := api.Authentication.AddRole(r.Context(), mux.Vars(r)["id"], newrole); err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	rw.Write([]byte("success"))
}

func (api *RestApi) updateConfiguration(rw http.ResponseWriter, r *http.Request) {
	rw.Header().Set("Content-Type", "text/plain")
	key, value := r.FormValue("key"), r.FormValue("value")

	fmt.Printf("KEY: %#v\nVALUE: %#v\n", key, value)

	if err := config.UpdateConfig(key, value, r.Context()); err != nil {
		http.Error(rw, err.Error(), http.StatusUnprocessableEntity)
		return
	}

	rw.Write([]byte("success"))
}

func (api *RestApi) putMachineState(rw http.ResponseWriter, r *http.Request) {
	if api.MachineStateDir == "" {
		http.Error(rw, "not enabled", http.StatusNotFound)
		return
	}

	vars := mux.Vars(r)
	cluster := vars["cluster"]
	host := vars["host"]
	dir := filepath.Join(api.MachineStateDir, cluster)
	if err := os.MkdirAll(dir, 0755); err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	filename := filepath.Join(dir, fmt.Sprintf("%s.json", host))
	f, err := os.Create(filename)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}
	defer f.Close()

	if _, err := io.Copy(f, r.Body); err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	rw.WriteHeader(http.StatusCreated)
}

func (api *RestApi) getMachineState(rw http.ResponseWriter, r *http.Request) {
	if api.MachineStateDir == "" {
		http.Error(rw, "not enabled", http.StatusNotFound)
		return
	}

	vars := mux.Vars(r)
	filename := filepath.Join(api.MachineStateDir, vars["cluster"], fmt.Sprintf("%s.json", vars["host"]))

	// Sets the content-type and 'Last-Modified' Header and so on automatically
	http.ServeFile(rw, r, filename)
}