package daemon

import (
	"errors"
	"fmt"
	"reflect"
	"slices"
	"strings"

	"guard/internal/bounty"
	"guard/internal/config"
	"guard/internal/match"
)

// Reloaded is what a reload changed.
type Reloaded struct {
	Changes []string `json:"changes"`
	// Restart are the changed settings a reload can't apply: they wait
	// for a restart.
	Restart []string `json:"restart,omitempty"`
}

// ReloadFile reads the configuration again (Load) and reloads it.
func (d *Daemon) ReloadFile() (*Reloaded, error) {
	if d.Load == nil {
		return nil, errors.New("this Guard can't read its configuration again")
	}
	cfg, err := d.Load()
	if err != nil {
		return nil, err
	}
	return d.Reload(cfg)
}

// Reload puts a new configuration to work without losing what Guard
// counted: a watch keeps its bounties and counts under the same name,
// and its source runs on unless it changed. Watches gone stop, new ones
// start. The housecarl connection, state, socket and log wait for a
// restart. A configuration with no watch at work is refused, and the
// old one stays.
func (d *Daemon) Reload(cfg *config.Config) (*Reloaded, error) {
	if d.ctx == nil {
		return nil, errors.New("Guard isn't running")
	}
	type next struct {
		cfg *config.Watch
		m   *match.Matcher
	}
	var want []next
	for _, w := range cfg.Watch {
		if w.Disabled {
			continue
		}
		m, err := match.Compile(w.Match, w.Ignore)
		if err != nil {
			return nil, fmt.Errorf("watch %s: %v", w.Name, err)
		}
		want = append(want, next{w, m})
	}
	if len(want) == 0 {
		return nil, errors.New("every watch is disabled: nothing to do (the configuration stays as it was)")
	}

	res := &Reloaded{}
	d.mu.Lock()
	old := d.cfg
	oh, nh := old.Housecarl, cfg.Housecarl
	oh.List, nh.List = "", "" // the default list only fills in watches
	if oh != nh {
		res.Restart = append(res.Restart, "housecarl")
	}
	if old.State != cfg.State {
		res.Restart = append(res.Restart, "state")
	}
	if old.Socket != cfg.Socket {
		res.Restart = append(res.Restart, "socket")
	}
	if old.Log != cfg.Log {
		res.Restart = append(res.Restart, "log")
	}
	cfg.Housecarl.URL, cfg.Housecarl.Socket, cfg.Housecarl.TokenFile, cfg.Housecarl.Token = old.Housecarl.URL, old.Housecarl.Socket, old.Housecarl.TokenFile, old.Housecarl.Token
	cfg.Housecarl.CACert, cfg.Housecarl.Insecure = old.Housecarl.CACert, old.Housecarl.Insecure
	cfg.State, cfg.Socket, cfg.Log = old.State, old.Socket, old.Log

	if !slices.Equal(old.NeverBan, cfg.NeverBan) {
		n := NewNeverBan(cfg.NeverBan, d.log)
		n.Lookup = d.never.Lookup
		d.never.mu.RLock()
		for _, h := range n.names {
			if a, ok := d.never.resolved[h]; ok {
				n.resolved[h] = a
			}
		}
		d.never.mu.RUnlock()
		d.neverStop()
		d.never = n
		d.startNever()
		res.Changes = append(res.Changes, "never_ban")
	}
	if old.Defaults.Repeat != cfg.Defaults.Repeat {
		res.Changes = append(res.Changes, "defaults.repeat: for the next bans")
	}

	byName := map[string]*Watch{}
	for _, w := range d.watches {
		byName[strings.ToLower(w.Cfg.Name)] = w
	}
	var watches []*Watch
	var stopped []chan struct{}
	for _, n := range want {
		w := byName[strings.ToLower(n.cfg.Name)]
		delete(byName, strings.ToLower(n.cfg.Name))
		if w == nil {
			w = &Watch{Cfg: n.cfg, Matcher: n.m, Tracker: bounty.New(n.cfg.Hits, n.cfg.Within.D())}
			d.start(w)
			watches = append(watches, w)
			res.Changes = append(res.Changes, "watch "+n.cfg.Name+": added")
			continue
		}
		watches = append(watches, w)
		oc, _ := w.setup()
		if reflect.DeepEqual(oc, n.cfg) {
			continue
		}
		var what []string
		if !slices.Equal(oc.Match, n.cfg.Match) || !slices.Equal(oc.Ignore, n.cfg.Ignore) {
			what = append(what, "patterns")
		}
		if oc.Hits != n.cfg.Hits || oc.Within != n.cfg.Within {
			what = append(what, fmt.Sprintf("bounty %d in %s", n.cfg.Hits, n.cfg.Within))
		}
		if !reflect.DeepEqual(oc.Ban, n.cfg.Ban) {
			what = append(what, "ban")
		}
		w.Tracker.Set(n.cfg.Hits, n.cfg.Within.D())
		w.mu.Lock()
		w.Cfg, w.Matcher = n.cfg, n.m
		w.mu.Unlock()
		if sourceKey(oc) != sourceKey(n.cfg) {
			w.stop()
			stopped = append(stopped, w.done)
			w.Source = d.newSource(n.cfg)
			d.start(w)
			what = append(what, "source (started again)")
		}
		if len(what) == 0 {
			what = append(what, "changed")
		}
		res.Changes = append(res.Changes, "watch "+n.cfg.Name+": "+strings.Join(what, ", "))
	}
	for _, w := range d.watches {
		if byName[strings.ToLower(w.Cfg.Name)] == w {
			w.stop()
			stopped = append(stopped, w.done)
			res.Changes = append(res.Changes, "watch "+w.Cfg.Name+": removed")
		}
	}
	d.watches = watches
	d.cfg = cfg
	d.mu.Unlock()

	// A stopped watch may be handling a line, which needs d.mu.
	for _, done := range stopped {
		<-done
	}
	d.loadGroups(d.ctx)
	if len(res.Changes) == 0 {
		res.Changes = []string{}
	}
	d.log.Info("reloaded", "changes", strings.Join(res.Changes, "; "))
	if len(res.Restart) > 0 {
		d.log.Warn("changed settings that wait for a restart", "settings", strings.Join(res.Restart, ", "))
	}
	return res, nil
}

// sourceKey is what a watch's source is made from: when it changes, the
// source starts again.
func sourceKey(w *config.Watch) string {
	j := ""
	if w.Journal != nil {
		j = fmt.Sprint(w.Journal.Unit, w.Journal.Identifier)
	}
	return fmt.Sprint(w.Kind(), "|", w.File, "|", j, "|", w.Source, "|", w.Protocol, "|", w.Shadow)
}