package main

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"syscall"
	"time"
	"unsafe"
)

var urgencies = []string{"low", "normal", "critical"}

const busTimeout = 10 * time.Second

// Notification is what node-notifier.send shows.
type Notification struct {
	Summary   string
	Body      string
	Urgency   string
	AppName   string
	Icon      string
	ExpireMS  int
	Category  string
	ReplaceID int
}

func notificationOf(args map[string]any) (Notification, error) {
	var n Notification
	var err error
	if n.Summary, err = text(args, "summary", true); err != nil {
		return n, err
	}
	if n.Body, err = text(args, "body", false); err != nil {
		return n, err
	}
	if n.Urgency, err = text(args, "urgency", false); err != nil {
		return n, err
	}
	if n.Urgency == "" {
		n.Urgency = "normal"
	}
	known := false
	for _, u := range urgencies {
		known = known || u == n.Urgency
	}
	if !known {
		return n, fmt.Errorf("urgency %q is low, normal or critical", n.Urgency)
	}
	if n.AppName, err = text(args, "app_name", false); err != nil {
		return n, err
	}
	if n.AppName == "" {
		n.AppName = "mesh"
	}
	if n.Icon, err = text(args, "icon", false); err != nil {
		return n, err
	}
	if n.ExpireMS, err = whole(args, "expire_ms", -1, 0, 24*3600*1000); err != nil {
		return n, err
	}
	if n.Category, err = text(args, "category", false); err != nil {
		return n, err
	}
	n.ReplaceID, err = whole(args, "replace_id", 0, 0, 1<<31-1)
	return n, err
}

// SendResult is what node-notifier.send answers.
type SendResult struct {
	ID int `json:"id"`
}

// Send shows a notification through the desktop's notification service, whichever runs it.
func Send(n Notification) (SendResult, error) {
	s, err := findBus()
	if err != nil {
		return SendResult{}, err
	}
	args := []string{"--print-id", "--urgency=" + n.Urgency, "--app-name=" + n.AppName}
	if n.Icon != "" {
		args = append(args, "--icon="+n.Icon)
	}
	if n.ExpireMS >= 0 {
		args = append(args, "--expire-time="+strconv.Itoa(n.ExpireMS))
	}
	if n.Category != "" {
		args = append(args, "--category="+n.Category)
	}
	if n.ReplaceID > 0 {
		args = append(args, "--replace-id="+strconv.Itoa(n.ReplaceID))
	}
	// "--" so a title that starts with a dash is a title.
	args = append(args, "--", n.Summary)
	if n.Body != "" {
		args = append(args, n.Body)
	}
	r, err := s.run(busTimeout, "", "notify-send", args...)
	if err != nil {
		return SendResult{}, err
	}
	if r.Code != 0 {
		return SendResult{}, fmt.Errorf("notify-send: %s", strings.TrimSpace(r.Stderr))
	}
	id, err := strconv.Atoi(strings.TrimSpace(r.Stdout))
	if err != nil {
		return SendResult{}, fmt.Errorf("notify-send answered no id: %q", r.Stdout)
	}
	return SendResult{ID: id}, nil
}

// dunstctl runs one dunstctl command over the session bus and answers what it printed.
func dunstctl(args ...string) (string, error) {
	s, err := findBus()
	if err != nil {
		return "", err
	}
	r, err := s.run(busTimeout, "", "dunstctl", args...)
	if err != nil {
		return "", err
	}
	if r.Code != 0 {
		return "", fmt.Errorf("dunstctl %s: %s", strings.Join(args, " "), strings.TrimSpace(r.Stderr+r.Stdout))
	}
	return r.Stdout, nil
}

// variantMaps reads busctl's JSON form of an array of dictionaries (aa{sv}), which is how dunstctl
// answers history and rules, into plain maps.
func variantMaps(raw string) ([]map[string]any, error) {
	var doc struct {
		Type string `json:"type"`
		Data [][]map[string]struct {
			Data any `json:"data"`
		} `json:"data"`
	}
	if err := json.Unmarshal([]byte(raw), &doc); err != nil {
		return nil, fmt.Errorf("dunstctl's answer is not the bus's JSON: %w", err)
	}
	if doc.Type != "aa{sv}" {
		return nil, fmt.Errorf("dunstctl answered %s, not aa{sv}", doc.Type)
	}
	out := []map[string]any{}
	for _, group := range doc.Data {
		for _, entry := range group {
			m := map[string]any{}
			for k, v := range entry {
				m[k] = v.Data
			}
			out = append(out, m)
		}
	}
	return out, nil
}

// Shown is one notification in the history.
type Shown struct {
	ID         int    `json:"id"`
	AppName    string `json:"app_name"`
	Summary    string `json:"summary"`
	Body       string `json:"body,omitempty"`
	Urgency    string `json:"urgency"`
	Category   string `json:"category,omitempty"`
	AgeSeconds int64  `json:"age_seconds"`
}

// HistoryResult is what node-notifier.history answers.
type HistoryResult struct {
	Total         int     `json:"total"`
	Notifications []Shown `json:"notifications"`
}

// History is dunst's history, newest first.
func History(limit int) (HistoryResult, error) {
	raw, err := dunstctl("history")
	if err != nil {
		return HistoryResult{}, err
	}
	return parseHistory(raw, monotonicMicros(), limit)
}

func parseHistory(raw string, nowMicros int64, limit int) (HistoryResult, error) {
	entries, err := variantMaps(raw)
	if err != nil {
		return HistoryResult{}, err
	}
	out := HistoryResult{Total: len(entries), Notifications: []Shown{}}
	type stamped struct {
		Shown
		at int64
	}
	var all []stamped
	for _, e := range entries {
		at := number(e["timestamp"])
		all = append(all, stamped{Shown{
			ID: int(number(e["id"])), AppName: str(e["appname"]), Summary: str(e["summary"]), Body: str(e["body"]),
			Urgency: strings.ToLower(str(e["urgency"])), Category: str(e["category"]),
			AgeSeconds: max(0, (nowMicros-at)/1_000_000),
		}, at})
	}
	sort.SliceStable(all, func(i, j int) bool { return all[i].at > all[j].at })
	for i, s := range all {
		if i == limit {
			break
		}
		out.Notifications = append(out.Notifications, s.Shown)
	}
	return out, nil
}

func number(v any) int64 {
	switch n := v.(type) {
	case float64:
		return int64(n)
	case json.Number:
		i, _ := n.Int64()
		return i
	}
	return 0
}

func str(v any) string {
	s, _ := v.(string)
	return s
}

// monotonicMicros is the clock dunst stamps its notifications with (CLOCK_MONOTONIC, microseconds).
func monotonicMicros() int64 {
	var ts syscall.Timespec
	const clockMonotonic = 1
	if _, _, errno := syscall.Syscall(syscall.SYS_CLOCK_GETTIME, clockMonotonic, uintptr(unsafe.Pointer(&ts)), 0); errno != 0 {
		return 0
	}
	return ts.Sec*1_000_000 + ts.Nsec/1000
}

// PauseResult is what dunst_pause and dunst_resume answer.
type PauseResult struct {
	Paused bool   `json:"paused"`
	Note   string `json:"note"`
}

// SetPaused turns do-not-disturb on or off.
func SetPaused(on bool) (PauseResult, error) {
	if _, err := dunstctl("set-paused", strconv.FormatBool(on)); err != nil {
		return PauseResult{}, err
	}
	out, err := dunstctl("is-paused")
	if err != nil {
		return PauseResult{}, err
	}
	paused := strings.TrimSpace(out) == "true"
	note := "notifications are shown"
	if paused {
		note = "notifications are held back until dunst_resume; the next login starts unpaused"
	}
	return PauseResult{Paused: paused, Note: note}, nil
}

// CloseAll closes what is on screen.
func CloseAll() (CountResult, error) {
	if _, err := dunstctl("close-all"); err != nil {
		return CountResult{}, err
	}
	return Count()
}

// CountResult is what dunst_count answers.
type CountResult struct {
	Displayed int  `json:"displayed"`
	Waiting   int  `json:"waiting"`
	History   int  `json:"history"`
	Paused    bool `json:"paused"`
}

// Count is how many notifications are where.
func Count() (CountResult, error) {
	var c CountResult
	for _, part := range []struct {
		which string
		into  *int
	}{{"displayed", &c.Displayed}, {"waiting", &c.Waiting}, {"history", &c.History}} {
		out, err := dunstctl("count", part.which)
		if err != nil {
			return c, err
		}
		n, err := strconv.Atoi(strings.TrimSpace(out))
		if err != nil {
			return c, fmt.Errorf("dunstctl count %s answered %q", part.which, out)
		}
		*part.into = n
	}
	out, err := dunstctl("is-paused")
	if err != nil {
		return c, err
	}
	c.Paused = strings.TrimSpace(out) == "true"
	return c, nil
}

// Rule is one notifier rule in force.
type Rule struct {
	Name    string         `json:"name"`
	Enabled bool           `json:"enabled"`
	Sets    map[string]any `json:"sets"`
}

// RulesResult is what dunst_rules answers.
type RulesResult struct {
	Files []string `json:"files"`
	Rules []Rule   `json:"rules"`
}

// Rules are the rules the running notifier holds, and the files it reads them from.
func Rules() (RulesResult, error) {
	raw, err := dunstctl("rules", "--json")
	if err != nil {
		return RulesResult{}, err
	}
	return parseRules(raw, configFiles(filepath.Join(operatorHome(), ".config", "dunst")))
}

func parseRules(raw string, files []string) (RulesResult, error) {
	entries, err := variantMaps(raw)
	if err != nil {
		return RulesResult{}, err
	}
	out := RulesResult{Files: files, Rules: []Rule{}}
	for _, e := range entries {
		r := Rule{Name: str(e["name"]), Enabled: e["enabled"] == true, Sets: map[string]any{}}
		for k, v := range e {
			if k != "name" && k != "enabled" {
				r.Sets[k] = v
			}
		}
		out.Rules = append(out.Rules, r)
	}
	sort.SliceStable(out.Rules, func(i, j int) bool { return out.Rules[i].Name < out.Rules[j].Name })
	return out, nil
}

// configFiles are dunstrc and its drop-ins in the order dunst reads them.
func configFiles(dir string) []string {
	files := []string{}
	if _, err := os.Stat(filepath.Join(dir, "dunstrc")); err == nil {
		files = append(files, filepath.Join(dir, "dunstrc"))
	}
	dropins, _ := filepath.Glob(filepath.Join(dir, "dunstrc.d", "*.conf"))
	sort.Strings(dropins)
	return append(files, dropins...)
}