package api

// The Space tab: what is using a disk or a pool. The unit is a whole volume, never a
// partition: a disk on its own is scanned through every filesystem it backs, and a ZFS pool
// through every mounted dataset, as one thing — its member disks are not scanned apart.

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

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

// spaceTarget is one thing a scan can measure: a disk on its own, or a ZFS pool as a whole.
// A disk that is a member of a pool is not a target of its own — its share of the pool means
// nothing by itself — it is listed under the pool. (A disk with a pool partition *and* a
// filesystem of its own, root on one partition and a pool on another, is both.)
type spaceTarget struct {
	ID     string      `json:"id"`   // "nvme0" or "pool:tank"
	Kind   string      `json:"kind"` // disk | pool
	Name   string      `json:"name"`
	Model  string      `json:"model,omitempty"`  // disk: its model
	Layout string      `json:"layout,omitempty"` // pool: raidz2, mirror, …
	Health string      `json:"health,omitempty"` // pool: ONLINE, DEGRADED, …
	Size   uint64      `json:"size"`
	Used   uint64      `json:"used,omitempty"`  // pool: allocated
	Disks  []string    `json:"disks,omitempty"` // pool: its member disks
	Roots  []string    `json:"roots"`           // the mountpoints a scan walks
	Scan   *space.Scan `json:"scan,omitempty"`  // the last scan, if any

	datasets map[string]string // root → ZFS dataset, for the ones that are
}

var layoutRe = regexp.MustCompile(`\b(draid\d*|raidz[123]?|mirror)\b`)

// spaceTargets lists the disks and pools a scan can measure.
func (s *Server) spaceTargets(ctx context.Context) []spaceTarget {
	devs, _ := storage.Devices(ctx)
	var out []spaceTarget
	pools := map[string]*spaceTarget{}
	var poolOrder []string
	for _, d := range devs {
		disk := spaceTarget{ID: d.Name, Kind: "disk", Name: d.Name, Model: d.Model, Size: d.Size, Roots: []string{}}
		seen := map[string]bool{}
		inPool := false
		for _, p := range d.Parts {
			if p.FSType == "zfs_member" && p.Label != "" {
				inPool = true
				pt := pools[p.Label]
				if pt == nil {
					pt = &spaceTarget{ID: "pool:" + p.Label, Kind: "pool", Name: p.Label, Roots: []string{}, datasets: map[string]string{}}
					for _, zm := range zfsMounts(ctx, p.Label) {
						pt.Roots = append(pt.Roots, zm.mount)
						pt.datasets[zm.mount] = zm.dataset
					}
					pools[p.Label] = pt
					poolOrder = append(poolOrder, p.Label)
				}
				pt.Disks = append(pt.Disks, d.Name)
				continue
			}
			if p.Mount != "" && p.Mount != "[SWAP]" && !seen[p.Mount] {
				seen[p.Mount] = true
				disk.Roots = append(disk.Roots, p.Mount)
			}
		}
		if !inPool || len(disk.Roots) > 0 {
			sort.Strings(disk.Roots)
			out = append(out, disk)
		}
	}
	if len(pools) > 0 {
		// size, health and layout from zpool; the vdev tree names the layout
		for _, p := range s.storage.ZFS(ctx).Pools {
			if pt := pools[p.Name]; pt != nil {
				pt.Size, pt.Used, pt.Health = p.Size, p.Alloc, p.Health
				if m := layoutRe.FindString(p.Config); m != "" {
					pt.Layout = m
				} else if len(pt.Disks) == 1 {
					pt.Layout = "single disk"
				} else if len(pt.Disks) > 1 {
					pt.Layout = "stripe"
				}
			}
		}
		var ps []spaceTarget
		for _, name := range poolOrder {
			sort.Strings(pools[name].Roots)
			ps = append(ps, *pools[name])
		}
		out = append(ps, out...) // pools first: they are what a NAS is
	}
	if out == nil {
		out = []spaceTarget{}
	}
	return out
}

type zfsMount struct{ mount, dataset string }

// zfsMounts is every mounted filesystem of a pool, with its dataset.
func zfsMounts(ctx context.Context, pool string) []zfsMount {
	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	out, err := exec.CommandContext(ctx, "zfs", "list", "-H", "-t", "filesystem", "-r", "-o", "name,mountpoint,mounted", pool).Output()
	if err != nil {
		return nil
	}
	var mounts []zfsMount
	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
		f := strings.Split(line, "\t")
		if len(f) == 3 && f[2] == "yes" && strings.HasPrefix(f[1], "/") {
			mounts = append(mounts, zfsMount{mount: f[1], dataset: f[0]})
		}
	}
	return mounts
}

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

func (s *Server) spaceTarget(w http.ResponseWriter, r *http.Request, id string) (spaceTarget, bool) {
	for _, t := range s.spaceTargets(r.Context()) {
		if t.ID == id {
			return t, true
		}
	}
	jsonErr(w, 404, "no such disk or pool")
	return spaceTarget{}, 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) {
	t, ok := s.spaceTarget(w, r, r.PathValue("disk"))
	if !ok {
		return
	}
	st, err := s.space.Start(t.ID, t.Roots, t.datasets)
	if err != nil {
		jsonErr(w, 409, err.Error())
		return
	}
	log.Printf("space: scan of %s (%s) started by %s", t.ID, strings.Join(t.Roots, " "), clientIP(r))
	jsonOK(w, 202, st)
}

func (s *Server) spaceForget(w http.ResponseWriter, r *http.Request) {
	s.space.Forget(r.PathValue("disk"))
	log.Printf("space: scan of %s forgotten by %s", r.PathValue("disk"), clientIP(r))
	w.WriteHeader(204)
}

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 > 32 {
		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)
}