// Package config loads and saves hamlab's JSON config file.
package config

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

	"hamlab/internal/store"
)

// Token is an API token another Ham Lab (a hub) uses to manage this host. Only the
// SHA-256 of the token is kept.
type Token struct {
	Name    string    `json:"name"`
	Hash    string    `json:"hash"`
	Created time.Time `json:"created"`
	// Scope is what the token may do. "" is everything (a hub's token: full control of
	// this machine). ScopeSensorsRead only reads sensors — what a dashboard gets.
	Scope string `json:"scope,omitempty"`
	// Sensors narrows a sensors:read token to the IDs these patterns match. Empty is all.
	Sensors []string `json:"sensors,omitempty"`
	// IssuedBy is the account that made the token (or paired the hub that holds it).
	IssuedBy string `json:"issued_by,omitempty"`
}

const ScopeSensorsRead = "sensors:read"

// Node is a remote Ham Lab this host (as hub) manages. The token is the one that
// node issued to us; the fingerprint pins its self-signed certificate.
type Node struct {
	Name        string    `json:"name"`
	URL         string    `json:"url"`
	Fingerprint string    `json:"fingerprint,omitempty"`
	Token       string    `json:"token"`
	Added       time.Time `json:"added"`
}

// User is an account on this machine's console. Only the argon2id hash is kept.
type User struct {
	Name     string    `json:"name"`
	Hash     string    `json:"hash"`
	Created  time.Time `json:"created"`
	LastSeen time.Time `json:"last_seen,omitempty"`
}

// UpdateSource is where this machine looks for a newer Ham Lab, and how often. The field
// is Updates, not Update, because Config already has an Update method.
type UpdateSource struct {
	// URL is a Gitea/Forgejo repo API base or a static directory; empty means the built-in
	// default, and "off" means never look.
	URL string `json:"url,omitempty"`
	// Token is sent when the source is behind a login, so a private Gitea can serve its
	// own fleet without the instance being opened to everyone.
	Token string `json:"token,omitempty"`
	// Check is "daily" (the default) or "never".
	Check string `json:"check,omitempty"`
}

// KVM is an IP-KVM: a device with a web page that gives screen, keyboard and mouse access
// to a machine, including when that machine has no OS running. Ham Lab holds the list on
// the hub and proxies each one, because a KVM matters exactly when the machine it is
// attached to cannot answer for itself.
type KVM struct {
	ID   string `json:"id"`
	Name string `json:"name"`
	// URL is the device's own address, as you would type it into a browser on the LAN.
	URL string `json:"url"`
	// Machine is the host this KVM is attached to, and is the key: one KVM per machine, shown
	// on that machine's KVM tab. Empty means the hub itself. The list lives on the hub even
	// for a node's KVM, because a KVM earns its keep when the machine is down and cannot
	// answer for itself.
	Machine string    `json:"machine"`
	Added   time.Time `json:"added"`
}

type Config struct {
	Listen string `json:"listen"`
	// PasswordHash is the single login of installs before users existed. On load it becomes
	// the first user (see MigrateUsers) and is then dropped from the file.
	PasswordHash string `json:"password_hash,omitempty"`
	Users        []User `json:"users,omitempty"`
	TLS          string  `json:"tls,omitempty"` // "auto" → self-signed cert in the data dir; "" → plain HTTP
	Tokens       []Token `json:"tokens,omitempty"`
	Nodes        []Node  `json:"nodes,omitempty"`
	KVMs         []KVM   `json:"kvms,omitempty"`
	// Updates: where a newer build comes from. See UpdateSource.
	Updates UpdateSource `json:"update,omitempty"`

	path string
	mu   sync.Mutex
}

// Candidates lists where config.json may live under a home directory, preferred first:
// the XDG location, then ~/apps/hamlab, which installs before v0.2 used.
func Candidates(home string) []string {
	return []string{filepath.Join(home, ".config", "hamlab", "config.json"), filepath.Join(home, "apps", "hamlab", "config.json")}
}

// DefaultPath is the config used when neither -config nor $HAMLAB_CONFIG says otherwise:
// whichever candidate exists, else the preferred one.
func DefaultPath() string {
	home, _ := os.UserHomeDir()
	c := Candidates(home)
	for _, p := range c {
		if _, err := os.Stat(p); err == nil {
			return p
		}
	}
	return c[0]
}

func Default(path string) *Config {
	return &Config{Listen: "127.0.0.1:8100", path: path}
}

// Load reads the config at path. A missing file yields the defaults.
func Load(path string) (*Config, error) {
	c := Default(path)
	b, err := os.ReadFile(path)
	if errors.Is(err, os.ErrNotExist) {
		return c, nil
	}
	if err != nil {
		return nil, err
	}
	if err := json.Unmarshal(b, c); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	return c, nil
}

// MigrateUsers turns the pre-users single password into the first account, named after
// the OS user the console runs as. Reports whether anything changed (the caller saves).
func (c *Config) MigrateUsers(name string) bool {
	if len(c.Users) > 0 || c.PasswordHash == "" {
		return false
	}
	c.Users = []User{{Name: name, Hash: c.PasswordHash, Created: time.Now()}}
	c.PasswordHash = ""
	return true
}

// User finds an account by name. Call under View/Update or on a config nobody else holds.
func (c *Config) User(name string) (User, bool) {
	for _, u := range c.Users {
		if u.Name == name {
			return u, true
		}
	}
	return User{}, false
}

func (c *Config) Path() string    { return c.path }
func (c *Config) DataDir() string { return filepath.Dir(c.path) }

func (c *Config) Save() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.save()
}

func (c *Config) save() error {
	if err := os.MkdirAll(c.DataDir(), 0o700); err != nil {
		return err
	}
	b, err := json.MarshalIndent(c, "", "  ")
	if err != nil {
		return err
	}
	return store.WriteFileAtomic(c.path, append(b, '\n'), 0o600)
}

// Update applies fn under the lock and saves.
func (c *Config) Update(fn func(*Config)) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	fn(c)
	return c.save()
}

// View reads under the lock.
func (c *Config) View(fn func(*Config)) {
	c.mu.Lock()
	defer c.mu.Unlock()
	fn(c)
}