// Package shares manages SMB (Samba) and NFS exports: the definitions live in
// /etc/nasmon/shares.json, from which nasmon generates /etc/samba/smb.conf and
// /etc/exports.d/nasmon.exports and reloads the daemons.
package shares

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

type SMBShare struct {
	Name         string   `json:"name"`
	Path         string   `json:"path"`
	Comment      string   `json:"comment"`
	ReadOnly     bool     `json:"read_only"`
	Guest        bool     `json:"guest"` // anyone on the LAN, no password
	Users        []string `json:"users"` // SMB users allowed when Guest is false
	Browseable   bool     `json:"browseable"`
	HideSysFiles bool     `json:"hide_sys_files"` // veto ._*, .DS_Store, Thumbs.db, desktop.ini
}

type SMBConfig struct {
	Enabled      bool       `json:"enabled"`
	Workgroup    string     `json:"workgroup"`
	ServerString string     `json:"server_string"`
	Shares       []SMBShare `json:"shares"`
}

type NFSExport struct {
	Path     string   `json:"path"`
	Clients  []string `json:"clients"` // host, IP, CIDR or *
	ReadOnly bool     `json:"read_only"`
	Squash   string   `json:"squash"` // root | all | none
	Async    bool     `json:"async"`
}

type NFSConfig struct {
	Enabled bool        `json:"enabled"`
	Exports []NFSExport `json:"exports"`
}

type Config struct {
	SMB SMBConfig `json:"smb"`
	NFS NFSConfig `json:"nfs"`
}

func Defaults() Config {
	return Config{
		SMB: SMBConfig{Enabled: true, Workgroup: "WORKGROUP", ServerString: "Home NAS"},
		NFS: NFSConfig{Enabled: true},
	}
}

// FindSMB returns the index of the share with that name, or -1.
func (c *Config) FindSMB(name string) int {
	for i, s := range c.SMB.Shares {
		if s.Name == name {
			return i
		}
	}
	return -1
}

// FindNFS returns the index of the export for that path, or -1.
func (c *Config) FindNFS(path string) int {
	for i, e := range c.NFS.Exports {
		if e.Path == path {
			return i
		}
	}
	return -1
}

func (c *Config) sortShares() {
	sort.Slice(c.SMB.Shares, func(i, j int) bool { return c.SMB.Shares[i].Name < c.SMB.Shares[j].Name })
	sort.Slice(c.NFS.Exports, func(i, j int) bool { return c.NFS.Exports[i].Path < c.NFS.Exports[j].Path })
}

// Validate checks the whole configuration (pure; no filesystem access).
func (c *Config) Validate() error {
	if err := ValidateWorkgroup(c.SMB.Workgroup); err != nil {
		return err
	}
	seen := map[string]bool{}
	for _, s := range c.SMB.Shares {
		if err := s.Validate(); err != nil {
			return err
		}
		if seen[s.Name] {
			return fmt.Errorf("duplicate share name %s", s.Name)
		}
		seen[s.Name] = true
	}
	paths := map[string]bool{}
	for _, e := range c.NFS.Exports {
		if err := e.Validate(); err != nil {
			return err
		}
		if paths[e.Path] {
			return fmt.Errorf("duplicate NFS export %s", e.Path)
		}
		paths[e.Path] = true
	}
	return nil
}

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

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)
	}
	st.cur.sortShares()
	return st, nil
}

func (st *Store) Get() Config {
	st.mu.RLock()
	defer st.mu.RUnlock()
	return st.cur.clone()
}

func (c Config) clone() Config {
	out := c
	out.SMB.Shares = make([]SMBShare, len(c.SMB.Shares))
	for i, s := range c.SMB.Shares {
		s.Users = append([]string(nil), s.Users...)
		out.SMB.Shares[i] = s
	}
	out.NFS.Exports = make([]NFSExport, len(c.NFS.Exports))
	for i, e := range c.NFS.Exports {
		e.Clients = append([]string(nil), e.Clients...)
		out.NFS.Exports[i] = e
	}
	return out
}

func (st *Store) Save(c Config) error {
	if err := c.Validate(); err != nil {
		return err
	}
	c.sortShares()
	b, err := json.MarshalIndent(c, "", "  ")
	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'), 0o644); err != nil {
		return err
	}
	if err := os.Rename(tmp, st.path); err != nil {
		return err
	}
	st.cur = c.clone()
	return nil
}