// Package config holds nasmon settings, persisted as a JSON file that is
// editable both by hand and through the web UI.
package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
)

type SMTP struct {
	Host          string   `json:"host"`
	Port          int      `json:"port"`
	Security      string   `json:"security"` // starttls | tls | none
	User          string   `json:"user"`
	Pass          string   `json:"pass"`
	From          string   `json:"from"`
	To            []string `json:"to"`
	SubjectPrefix string   `json:"subject_prefix"`
}

type Thresholds struct {
	DiskTempC       int `json:"disk_temp_c"`
	CPUTempC        int `json:"cpu_temp_c"`
	PoolCapacityPct int `json:"pool_capacity_pct"`
	ScrubMaxAgeDays int `json:"scrub_max_age_days"`
	RootFSFreePct   int `json:"rootfs_free_pct"`
	NVMeUsedPct     int `json:"nvme_used_pct"`
	NVMeSparePct    int `json:"nvme_spare_pct"`
}

type SelfTests struct {
	Enabled   bool `json:"enabled"`
	ShortDays int  `json:"short_days"`
	LongDays  int  `json:"long_days"`
	Hour      int  `json:"hour"` // local hour of day when tests may be started
}

type Settings struct {
	SMTP             SMTP       `json:"smtp"`
	AlertsEnabled    bool       `json:"alerts_enabled"`
	NotifyResolved   bool       `json:"notify_resolved"`
	RemindHours      int        `json:"remind_hours"`
	SmartIntervalMin int        `json:"smart_interval_min"`
	SmartSkipStandby bool       `json:"smart_skip_standby"`
	Thresholds       Thresholds `json:"thresholds"`
	SelfTests        SelfTests  `json:"self_tests"`
}

func Defaults() Settings {
	return Settings{
		SMTP:             SMTP{Port: 587, Security: "starttls", SubjectPrefix: "[nasmon]"},
		AlertsEnabled:    true,
		NotifyResolved:   true,
		RemindHours:      24,
		SmartIntervalMin: 30,
		SmartSkipStandby: true,
		Thresholds: Thresholds{
			DiskTempC:       50,
			CPUTempC:        80,
			PoolCapacityPct: 85,
			ScrubMaxAgeDays: 45,
			RootFSFreePct:   10,
			NVMeUsedPct:     90,
			NVMeSparePct:    10,
		},
		SelfTests: SelfTests{Enabled: false, ShortDays: 7, LongDays: 30, Hour: 3},
	}
}

// Validate normalises and checks values coming from the web form.
func (s *Settings) Validate() error {
	s.SMTP.Security = strings.ToLower(strings.TrimSpace(s.SMTP.Security))
	switch s.SMTP.Security {
	case "starttls", "tls", "none":
	default:
		return fmt.Errorf("smtp security must be starttls, tls or none")
	}
	if s.SMTP.Port <= 0 || s.SMTP.Port > 65535 {
		return errors.New("smtp port out of range")
	}
	var to []string
	for _, a := range s.SMTP.To {
		if a = strings.TrimSpace(a); a != "" {
			to = append(to, a)
		}
	}
	s.SMTP.To = to
	if s.RemindHours < 0 {
		return errors.New("remind hours must be >= 0")
	}
	if s.SmartIntervalMin < 1 {
		return errors.New("SMART interval must be >= 1 minute")
	}
	if s.SelfTests.Hour < 0 || s.SelfTests.Hour > 23 {
		return errors.New("self-test hour must be 0..23")
	}
	if s.SelfTests.ShortDays < 0 || s.SelfTests.LongDays < 0 {
		return errors.New("self-test periods must be >= 0")
	}
	return nil
}

// Store is a thread-safe holder for the current settings backed by a file.
type Store struct {
	path string
	mu   sync.RWMutex
	cur  Settings
}

func Load(path string) (*Store, error) {
	st := &Store{path: path, cur: Defaults()}
	b, err := os.ReadFile(path)
	switch {
	case errors.Is(err, os.ErrNotExist):
		return st, nil
	case err != nil:
		return nil, err
	}
	if err := json.Unmarshal(b, &st.cur); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	return st, nil
}

func (st *Store) Get() Settings {
	st.mu.RLock()
	defer st.mu.RUnlock()
	s := st.cur
	s.SMTP.To = append([]string(nil), s.SMTP.To...)
	return s
}

func (st *Store) Save(s Settings) error {
	if err := s.Validate(); err != nil {
		return err
	}
	b, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return err
	}
	st.mu.Lock()
	defer st.mu.Unlock()
	if err := os.MkdirAll(filepath.Dir(st.path), 0o755); err != nil {
		return err
	}
	tmp := st.path + ".tmp"
	if err := os.WriteFile(tmp, append(b, '\n'), 0o600); err != nil {
		return err
	}
	if err := os.Rename(tmp, st.path); err != nil {
		return err
	}
	st.cur = s
	return nil
}