// Package web serves the dashboard, settings form and JSON API.
package web

import (
	"embed"
	"fmt"
	"html/template"
	"io/fs"
	"log"
	"math"
	"net"
	"net/http"
	"net/url"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"nasmon/internal/alert"
	"nasmon/internal/config"
	"nasmon/internal/history"
	"nasmon/internal/hostrun"
	"nasmon/internal/sched"
	"nasmon/internal/shares"
	"nasmon/internal/store"
	"nasmon/internal/zfsadm"
)

//go:embed templates/*.html static/*
var assets embed.FS

type Server struct {
	cfg    *config.Store
	st     *store.Store
	ring   *history.Ring
	sch    *sched.Scheduler
	send   func(config.SMTP, string, string) error
	admin  *zfsadm.Admin
	shares *shares.Store
	shm    *shares.Manager
	pages  map[string]*template.Template
	mux    *http.ServeMux

	// share path checks; replaced in tests
	dirExists  func(string) bool
	realPath   func(string) (string, error)
	readMounts func() string

	mu       sync.Mutex
	shareErr string // last failed Apply of the share config
}

func New(cfg *config.Store, st *store.Store, ring *history.Ring, sch *sched.Scheduler, sh *shares.Store) *Server {
	run := hostrun.Auto()
	s := &Server{cfg: cfg, st: st, ring: ring, sch: sch, send: alert.SendMail,
		admin: zfsadm.New(zfsadm.NoInput(run)), shares: sh, shm: shares.New(run),
		dirExists: statDir, realPath: filepath.EvalSymlinks, readMounts: procMounts, mux: http.NewServeMux()}
	s.pages = map[string]*template.Template{}
	layout := template.Must(template.New("layout").Funcs(funcs).ParseFS(assets, "templates/layout.html"))
	for _, name := range []string{"dashboard", "disk", "zfs", "alerts", "settings", "shares"} {
		t := template.Must(template.Must(layout.Clone()).ParseFS(assets, "templates/"+name+".html"))
		s.pages[name] = t
	}
	static, _ := fs.Sub(assets, "static")
	// embedded files carry no modtime, so tell browsers to re-fetch them:
	// otherwise a stale app.js can survive an upgrade until a hard reload
	files := http.StripPrefix("/static/", http.FileServer(http.FS(static)))
	s.mux.Handle("GET /static/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "no-cache")
		files.ServeHTTP(w, r)
	}))
	s.mux.HandleFunc("GET /{$}", s.dashboard)
	s.mux.HandleFunc("GET /disks/{serial}", s.disk)
	s.mux.HandleFunc("POST /disks/{serial}/forget", s.forgetDisk)
	s.mux.HandleFunc("GET /zfs", s.zfs)
	s.mux.HandleFunc("POST /zfs/create", s.zfsCreate)
	s.mux.HandleFunc("POST /zfs/destroy", s.zfsDestroy)
	s.mux.HandleFunc("POST /zfs/dedup", s.zfsDedup)
	s.mux.HandleFunc("GET /alerts", s.alerts)
	s.mux.HandleFunc("POST /alerts/{id}/{action}", s.alertAction)
	s.mux.HandleFunc("GET /shares", s.sharesPage)
	s.mux.HandleFunc("POST /shares/apply", s.sharesApply)
	s.mux.HandleFunc("POST /shares/smb/settings", s.smbSettings)
	s.mux.HandleFunc("POST /shares/smb/save", s.smbSave)
	s.mux.HandleFunc("POST /shares/smb/delete", s.smbDelete)
	s.mux.HandleFunc("POST /shares/nfs/settings", s.nfsSettings)
	s.mux.HandleFunc("POST /shares/nfs/save", s.nfsSave)
	s.mux.HandleFunc("POST /shares/nfs/delete", s.nfsDelete)
	s.mux.HandleFunc("POST /shares/users/save", s.userSave)
	s.mux.HandleFunc("POST /shares/users/delete", s.userDelete)
	s.mux.HandleFunc("GET /settings", s.settings)
	s.mux.HandleFunc("POST /settings", s.settingsPost)
	s.mux.HandleFunc("POST /smart/run", s.smartRun)
	s.mux.HandleFunc("GET /api/status", s.apiStatus)
	s.mux.HandleFunc("GET /api/history", s.apiHistory)
	s.mux.HandleFunc("GET /api/disks/{serial}/history", s.apiDiskHistory)
	return s
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) { s.mux.ServeHTTP(w, r) }

type pageData struct {
	Title   string
	Page    string
	Partial bool
	Alerts  int
	Data    any
	Flash   string
	Error   string
	RepoISO string // browser URL of the RepoISO portal ("" = integration off)
}

// render writes a full page, or only the "content" block when ?partial=1 is
// requested by the auto-refresh script.
func (s *Server) render(w http.ResponseWriter, r *http.Request, name string, pd pageData) {
	pd.Page = name
	pd.Partial = r.URL.Query().Get("partial") == "1"
	pd.RepoISO = browserURL(s.cfg.Get().Integrations.RepoISOURL, r.Host)
	if pd.Alerts == 0 {
		pd.Alerts = len(s.sch.Status().Alerts)
	}
	t := s.pages[name]
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("X-Alerts-Open", fmt.Sprint(pd.Alerts))
	block := "layout"
	if pd.Partial {
		block = "content"
	}
	if err := t.ExecuteTemplate(w, block, pd); err != nil {
		log.Printf("render %s: %v", name, err)
	}
}

// ---- template helpers

var funcs = template.FuncMap{
	"bytes": humanBytes,
	"pct": func(part, total uint64) float64 {
		if total == 0 {
			return 0
		}
		return math.Round(float64(part)*1000/float64(total)) / 10
	},
	"f1":  func(f float64) string { return fmt.Sprintf("%.1f", f) },
	"f0":  func(f float64) string { return fmt.Sprintf("%.0f", f) },
	"ago": ago,
	"agop": func(t *time.Time) string {
		if t == nil {
			return "never"
		}
		return ago(*t)
	},
	"capClass": func(pct, warn, crit int) string {
		switch {
		case pct >= crit:
			return "crit"
		case pct >= warn:
			return "warn"
		}
		return "ok"
	},
	"dt": func(t time.Time) string {
		if t.IsZero() {
			return "—"
		}
		return t.Local().Format("2006-01-02 15:04")
	},
	"dtp": func(t *time.Time) string {
		if t == nil {
			return "—"
		}
		return t.Local().Format("2006-01-02 15:04")
	},
	"hours": func(h int64) string { return fmt.Sprintf("%d h (%.1f y)", h, float64(h)/8760) },
	"dur":   func(sec float64) string { return (time.Duration(sec) * time.Second).Truncate(time.Minute).String() },
	"levelClass": func(pct float64, warn, crit float64) string {
		switch {
		case pct >= crit:
			return "crit"
		case pct >= warn:
			return "warn"
		}
		return "ok"
	},
	"tempClass": func(v any, warn int) string {
		c := toFloat(v)
		switch {
		case warn > 0 && c >= float64(warn):
			return "crit"
		case warn > 0 && c >= float64(warn)-8:
			return "warn"
		}
		return "ok"
	},
	"healthClass": func(h string) string {
		switch h {
		case "ONLINE":
			return "ok"
		case "DEGRADED":
			return "warn"
		}
		return "crit"
	},
	"unix":      func(t int64) time.Time { return time.Unix(t, 0) },
	"join":      strings.Join,
	"hasPrefix": strings.HasPrefix,
	"contains": func(list []string, x string) bool {
		for _, v := range list {
			if v == x {
				return true
			}
		}
		return false
	},
	"repeat": strings.Repeat,
	"lines":  func(s string) []string { return strings.Split(s, "\n") },
	"seq": func(n int) []int {
		out := make([]int, n)
		for i := range out {
			out[i] = i
		}
		return out
	},
}

func toFloat(v any) float64 {
	switch n := v.(type) {
	case int:
		return float64(n)
	case int64:
		return float64(n)
	case float64:
		return n
	}
	return 0
}

func humanBytes(b uint64) string {
	const unit = 1024
	if b < unit {
		return fmt.Sprintf("%d B", b)
	}
	div, exp := uint64(unit), 0
	for n := b / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(b)/float64(div), "KMGTPE"[exp])
}

func ago(t time.Time) string {
	if t.IsZero() {
		return "never"
	}
	d := time.Since(t)
	switch {
	case d < time.Minute:
		return "just now"
	case d < time.Hour:
		return fmt.Sprintf("%d min ago", int(d.Minutes()))
	case d < 48*time.Hour:
		return fmt.Sprintf("%d h ago", int(d.Hours()))
	}
	return fmt.Sprintf("%d days ago", int(d.Hours()/24))
}

// sparkline renders values as an inline SVG polyline. max<=0 means autoscale.
func sparkline(vals []float64, max float64, class string) template.HTML {
	const w, h = 240.0, 40.0
	if len(vals) < 2 {
		return template.HTML(fmt.Sprintf(`<svg class="spark %s" viewBox="0 0 %d %d" preserveAspectRatio="none"></svg>`, class, int(w), int(h)))
	}
	if max <= 0 {
		for _, v := range vals {
			if v > max {
				max = v
			}
		}
		if max == 0 {
			max = 1
		}
		max *= 1.1
	}
	var pts strings.Builder
	for i, v := range vals {
		x := w * float64(i) / float64(len(vals)-1)
		y := h - h*math.Min(v, max)/max
		fmt.Fprintf(&pts, "%.1f,%.1f ", x, y)
	}
	p := strings.TrimSpace(pts.String())
	return template.HTML(fmt.Sprintf(
		`<svg class="spark %s" viewBox="0 0 %d %d" preserveAspectRatio="none"><polygon points="0,%d %s %d,%d"/><polyline points="%s"/></svg>`,
		class, int(w), int(h), int(h), p, int(w), int(h), p))
}

// browserURL turns the configured RepoISO address into one the user's browser
// can open: a loopback host is replaced by the host the browser used for nasmon.
func browserURL(cfg, reqHost string) string {
	if cfg == "" {
		return ""
	}
	u, err := url.Parse(cfg)
	if err != nil || u.Host == "" {
		return cfg
	}
	switch u.Hostname() {
	case "127.0.0.1", "localhost", "::1":
		host := reqHost
		if h, _, err := net.SplitHostPort(reqHost); err == nil {
			host = h
		}
		if host == "" {
			return cfg
		}
		if strings.Contains(host, ":") {
			host = "[" + host + "]"
		}
		if p := u.Port(); p != "" {
			host += ":" + p
		}
		u.Host = host
	}
	return u.String()
}