package api

import (
	"net/http"
	"syscall"
	"time"

	"git.fabledsword.com/bvandeusen/minstrel/internal/buildinfo"
	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/logging"
)

// The admin Overview's status sections (M504): after the verdict, who is
// listening, what is downloading, what the library holds and how much room
// it has, and how the server itself is doing. One read for the page, polled
// while it is open.

type listeningView struct {
	Username    string `json:"username"`
	TrackID     string `json:"track_id"`
	Title       string `json:"title"`
	ArtistName  string `json:"artist_name"`
	AlbumID     string `json:"album_id"`
	AlbumTitle  string `json:"album_title"`
	DurationMs  int32  `json:"duration_ms"`
	StartedAt   string `json:"started_at"`
	Client      string `json:"client"`
	DeviceClass string `json:"device_class"`
}

type listeningStatusView struct {
	Now []listeningView `json:"now"`
	// The last day: how many plays, by how many people, the latest when.
	PlaysDay     int64   `json:"plays_day"`
	ListenersDay int64   `json:"listeners_day"`
	LastPlayAt   *string `json:"last_play_at"`
}

type downloadsStatusView struct {
	Running       int64   `json:"running"`
	NeedsYou      int64   `json:"needs_you"`
	NeedsYouSince *string `json:"needs_you_since"`
	ImportedDay   int64   `json:"imported_day"`
	GivenUpDay    int64   `json:"given_up_day"`
	// Live is the downloads not yet ended, the ones needing a person first.
	Live        []downloadView   `json:"live"`
	ClientsDown []clientDownView `json:"clients_down"`
}

// diskView is the filesystem one library folder, or the data folder, sits
// on.
type diskView struct {
	Path string `json:"path"`
	// Data marks Minstrel's own data folder (covers, fingerprints), beside
	// the library's.
	Data       bool   `json:"data,omitempty"`
	TotalBytes uint64 `json:"total_bytes"`
	FreeBytes  uint64 `json:"free_bytes"`
	// Error says why the folder could not be read, which is itself the
	// news: a drive that did not mount.
	Error string `json:"error,omitempty"`
}

type libraryStatusView struct {
	Tracks  int64      `json:"tracks"`
	Albums  int64      `json:"albums"`
	Artists int64      `json:"artists"`
	Bytes   int64      `json:"bytes"`
	Disks   []diskView `json:"disks"`
}

type serverErrorView struct {
	At      string `json:"at"`
	Message string `json:"message"`
	Attrs   string `json:"attrs"`
}

type serverStatusView struct {
	Version   string `json:"version"`
	Channel   string `json:"channel"`
	StartedAt string `json:"started_at"`
	// Migration is the database schema's version, and Dirty whether its
	// last migration stopped part way.
	Migration int64 `json:"migration"`
	Dirty     bool  `json:"dirty"`
	// Errors is the newest few errors logged since the start, newest first;
	// ErrorCount is all of them.
	Errors     []serverErrorView `json:"errors"`
	ErrorCount int64             `json:"error_count"`
}

type adminStatusView struct {
	Listening listeningStatusView `json:"listening"`
	Downloads downloadsStatusView `json:"downloads"`
	Library   libraryStatusView   `json:"library"`
	Server    serverStatusView    `json:"server"`
}

// overviewLiveDownloads is how many running downloads the Overview lists;
// Activity has the rest.
const overviewLiveDownloads = 5

// overviewErrors is how many recent errors the Overview lists.
const overviewErrors = 10

// handleGetAdminStatus implements GET /api/admin/status.
func (h *handlers) handleGetAdminStatus(w http.ResponseWriter, r *http.Request) {
	q := dbq.New(h.pool)
	ctx := r.Context()
	var out adminStatusView

	now, err := q.ListListeningNow(ctx)
	if err != nil {
		h.logger.Error("admin status: listening", "err", err)
		writeAdminJSONErr(w, http.StatusInternalServerError, "server_error")
		return
	}
	out.Listening.Now = make([]listeningView, 0, len(now))
	for _, p := range now {
		out.Listening.Now = append(out.Listening.Now, listeningView{
			Username: p.Username, TrackID: uuidToString(p.TrackID), Title: p.TrackTitle,
			ArtistName: p.ArtistName, AlbumID: uuidToString(p.AlbumID), AlbumTitle: p.AlbumTitle,
			DurationMs: p.DurationMs, StartedAt: formatTimestamp(p.StartedAt),
			Client: deref(p.ClientID), DeviceClass: deref(p.DeviceClass),
		})
	}
	day, err := q.PlaysLastDay(ctx)
	if err != nil {
		h.logger.Error("admin status: plays", "err", err)
		writeAdminJSONErr(w, http.StatusInternalServerError, "server_error")
		return
	}
	out.Listening.PlaysDay, out.Listening.ListenersDay = day.Plays, day.Listeners
	if day.LastAt.Valid {
		at := formatTimestamp(day.LastAt)
		out.Listening.LastPlayAt = &at
	}

	if err := h.downloadsStatus(r, q, &out.Downloads); err != nil {
		h.logger.Error("admin status: downloads", "err", err)
		writeAdminJSONErr(w, http.StatusInternalServerError, "server_error")
		return
	}

	lib, err := q.LibraryStatus(ctx)
	if err != nil {
		h.logger.Error("admin status: library", "err", err)
		writeAdminJSONErr(w, http.StatusInternalServerError, "server_error")
		return
	}
	out.Library = libraryStatusView{Tracks: lib.Tracks, Albums: lib.Albums, Artists: lib.Artists,
		Bytes: lib.Bytes, Disks: []diskView{}}
	if h.importer != nil {
		for _, root := range h.importer.Roots() {
			out.Library.Disks = append(out.Library.Disks, diskOf(root))
		}
	}
	if h.dataDir != "" {
		d := diskOf(h.dataDir)
		d.Data = true
		out.Library.Disks = append(out.Library.Disks, d)
	}

	out.Server = serverStatus(logging.Errors)
	// golang-migrate's own table, outside sqlc's schema.
	if err := h.pool.QueryRow(ctx, `SELECT version, dirty FROM schema_migrations LIMIT 1`).
		Scan(&out.Server.Migration, &out.Server.Dirty); err != nil {
		h.logger.Warn("admin status: migration version", "err", err)
	}
	writeJSON(w, http.StatusOK, out)
}

func (h *handlers) downloadsStatus(r *http.Request, q *dbq.Queries, out *downloadsStatusView) error {
	st, err := q.DownloadsStatus(r.Context())
	if err != nil {
		return err
	}
	*out = downloadsStatusView{Running: st.Running, NeedsYou: st.NeedsYou,
		ImportedDay: st.ImportedDay, GivenUpDay: st.GivenUpDay,
		Live: []downloadView{}, ClientsDown: []clientDownView{}}
	if st.NeedsYou > 0 && st.NeedsYouSince.Valid {
		since := formatTimestamp(st.NeedsYouSince)
		out.NeedsYouSince = &since
	}
	// ListGrabs puts the ones needing a person first, then the running ones.
	rows, err := q.ListGrabs(r.Context(), dbq.ListGrabsParams{MaxRows: overviewLiveDownloads})
	if err != nil {
		return err
	}
	for _, g := range rows {
		if !g.EndedAt.Valid {
			out.Live = append(out.Live, downloadFrom(g))
		}
	}
	down, err := q.ListClientsDown(r.Context())
	if err != nil {
		return err
	}
	for _, c := range down {
		out.ClientsDown = append(out.ClientsDown, clientDownView{Client: c.Client, Detail: c.Detail,
			Since: formatTimestamp(c.FirstSeen)})
	}
	return nil
}

// diskOf reads the size and free space of the filesystem path is on.
func diskOf(path string) diskView {
	var st syscall.Statfs_t
	if err := syscall.Statfs(path, &st); err != nil {
		return diskView{Path: path, Error: err.Error()}
	}
	bsize := uint64(st.Bsize)
	return diskView{Path: path, TotalBytes: st.Blocks * bsize, FreeBytes: st.Bavail * bsize}
}

func serverStatus(ring *logging.ErrorRing) serverStatusView {
	kept, total := ring.Snapshot()
	v := serverStatusView{Version: buildinfo.Version, Channel: buildinfo.Channel,
		StartedAt: buildinfo.Started.UTC().Format(time.RFC3339), ErrorCount: total,
		Errors: make([]serverErrorView, 0, min(len(kept), overviewErrors))}
	for i, e := range kept {
		if i == overviewErrors {
			break
		}
		v.Errors = append(v.Errors, serverErrorView{At: e.At.UTC().Format(time.RFC3339),
			Message: e.Message, Attrs: e.Attrs})
	}
	return v
}