package api

// The Space tab: what is using a disk. A disk is picked, not a partition: the scan covers
// every filesystem the disk backs — its partitions' mountpoints, and for a disk in a ZFS
// pool, every mounted dataset of that pool (so any of the pool's disks shows the pool).

import (
	"context"
	"log"
	"net/http"
	"os/exec"
	"sort"
	"strconv"
	"strings"
	"time"

	"hamlab/internal/space"
	"hamlab/internal/storage"
)

type spaceDisk struct {
	Name  string      `json:"name"`
	Kind  string      `json:"kind"`
	Model string      `json:"model,omitempty"`
	Size  uint64      `json:"size"`
	Pool  string      `json:"pool,omitempty"`  // the ZFS pool this disk is part of
	Roots []string    `json:"roots"`           // the mountpoints a scan walks
	Scan  *space.Scan `json:"scan,omitempty"` // the last scan, if any
}

// spaceDisks maps every disk to the mountpoints it backs.
func (s *Server) spaceDisks(ctx context.Context) []spaceDisk {
	devs, _ := storage.Devices(ctx)
	var out []spaceDisk
	poolMounts := map[string][]string{}
	for _, d := range devs {
		sd := spaceDisk{Name: d.Name, Kind: d.Kind, Model: d.Model, Size: d.Size, Roots: []string{}}
		seen := map[string]bool{}
		for _, p := range d.Parts {
			if p.Mount != "" && p.Mount != "[SWAP]" && !seen[p.Mount] {
				seen[p.Mount] = true
				sd.Roots = append(sd.Roots, p.Mount)
			}
			if p.FSType == "zfs_member" && p.Label != "" && sd.Pool == "" {
				sd.Pool = p.Label
			}
		}
		if sd.Pool != "" {
			mounts, ok := poolMounts[sd.Pool]
			if !ok {
				mounts = zfsMounts(ctx, sd.Pool)
				poolMounts[sd.Pool] = mounts
			}
			for _, m := range mounts {
				if !seen[m] {
					seen[m] = true
					sd.Roots = append(sd.Roots, m)
				}
			}
		}
		sort.Strings(sd.Roots)
		out = append(out, sd)
	}
	if out == nil {
		out = []spaceDisk{}
	}
	return out
}

// zfsMounts is every mounted filesystem of a pool.
func zfsMounts(ctx context.Context, pool string) []string {
	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	out, err := exec.CommandContext(ctx, "zfs", "list", "-H", "-t", "filesystem", "-r", "-o", "mountpoint,mounted", pool).Output()
	if err != nil {
		return nil
	}
	var mounts []string
	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
		f := strings.Split(line, "\t")
		if len(f) == 2 && f[1] == "yes" && strings.HasPrefix(f[0], "/") {
			mounts = append(mounts, f[0])
		}
	}
	return mounts
}

func (s *Server) spaceOverview(w http.ResponseWriter, r *http.Request) {
	disks := s.spaceDisks(r.Context())
	scans := s.space.All()
	for i := range disks {
		disks[i].Scan = scans[disks[i].Name]
	}
	jsonOK(w, 200, map[string]any{"disks": disks})
}

func (s *Server) spaceDisk(w http.ResponseWriter, r *http.Request, name string) (spaceDisk, bool) {
	for _, d := range s.spaceDisks(r.Context()) {
		if d.Name == name {
			return d, true
		}
	}
	jsonErr(w, 404, "no such disk")
	return spaceDisk{}, false
}

func (s *Server) spaceStatus(w http.ResponseWriter, r *http.Request) {
	st := s.space.Status(r.PathValue("disk"))
	if st == nil {
		jsonErr(w, 404, "not scanned")
		return
	}
	jsonOK(w, 200, st)
}

func (s *Server) spaceScan(w http.ResponseWriter, r *http.Request) {
	d, ok := s.spaceDisk(w, r, r.PathValue("disk"))
	if !ok {
		return
	}
	st, err := s.space.Start(d.Name, d.Roots)
	if err != nil {
		jsonErr(w, 409, err.Error())
		return
	}
	log.Printf("space: scan of %s (%s) started by %s", d.Name, strings.Join(d.Roots, " "), clientIP(r))
	jsonOK(w, 202, st)
}

func (s *Server) spaceCancel(w http.ResponseWriter, r *http.Request) {
	if !s.space.Cancel(r.PathValue("disk")) {
		jsonErr(w, 404, "no scan running")
		return
	}
	w.WriteHeader(204)
}

func (s *Server) spaceTree(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()
	path := q.Get("path")
	if path == "" {
		path = "/"
	}
	depth, _ := strconv.Atoi(q.Get("depth"))
	if depth < 1 || depth > 16 {
		depth = 1
	}
	limit, _ := strconv.Atoi(q.Get("limit"))
	if limit < 1 || limit > 2000 {
		limit = 300
	}
	min, _ := strconv.ParseInt(q.Get("min"), 10, 64)
	if min < 0 {
		min = 0
	}
	t, err := s.space.Tree(r.PathValue("disk"), path, depth, limit, min)
	if err != nil {
		jsonErr(w, 404, err.Error())
		return
	}
	w.Header().Set("Cache-Control", "no-store")
	jsonOK(w, 200, t)
}

func (s *Server) spaceLargest(w http.ResponseWriter, r *http.Request) {
	n, _ := strconv.Atoi(r.URL.Query().Get("n"))
	if n < 1 || n > 5000 {
		n = 500
	}
	files, err := s.space.Largest(r.PathValue("disk"), n)
	if err != nil {
		jsonErr(w, 404, err.Error())
		return
	}
	if files == nil {
		files = []space.File{}
	}
	jsonOK(w, 200, files)
}