// Package config loads the Compass/NHS service configuration from the process
// environment. Every secret comes from the environment (environment.d); nothing
// is compiled into the binary and nothing secret is read from a committed file.
package config

import (
	"errors"
	"fmt"
	"log/slog"
	"os"
	"strconv"
	"strings"
	"time"
	// Embed the IANA time zone database so SCHOOL_TIMEZONE resolves even in a
	// container without tzdata.
	_ "time/tzdata"
)

// Config is the fully resolved runtime configuration.
type Config struct {
	// Addr is the listen address, for example ":8792".
	Addr string
	// DBPath is the SQLite database file, for example "/data/school.db".
	DBPath string
	// SessionSecret signs the session cookie. Required, >= 16 bytes.
	SessionSecret []byte
	// AdminUsername is the single dashboard login name (Sam).
	AdminUsername string
	// AdminPassword is the plaintext password. Optional if AdminPasswordHash is set.
	AdminPassword string
	// AdminPasswordHash is a bcrypt hash. Optional if AdminPassword is set.
	AdminPasswordHash string
	// CookieSecure sets the Secure attribute on cookies. Keep true behind HTTPS.
	CookieSecure bool
	// SessionTTL is how long a session cookie stays valid.
	SessionTTL time.Duration
	// LogLevel is the slog level.
	LogLevel slog.Level
	// AppEnv is a label such as "production" or "development".
	AppEnv string
	// Version is injected at build time.
	Version string
	// Location is the family timezone. Due dates and briefs are wall-clock, so
	// this must be the family's zone, not the container default of UTC.
	Location *time.Location
	// Calendar is the Home Assistant calendar target for important school
	// events (AGENTS.md §4 FR-8).
	Calendar CalendarConfig
	// Apprise is the notification gateway for the morning briefs (FR-9,
	// FR-14).
	Apprise AppriseConfig
	// HubToken authenticates the Hub API (AGENTS.md §4 FR-11):
	// GET /capabilities, POST /ask and POST /notify. It is a shared
	// service-to-service secret; the Hub sends it. When it is empty those
	// endpoints answer 503 and nothing else changes.
	HubToken string
}

// HubConfigured reports whether the Hub API can serve authenticated requests.
func (c *Config) HubConfigured() bool {
	return strings.TrimSpace(c.HubToken) != ""
}

// CalendarConfig points at Sam's Home Assistant calendar. Every value comes
// from the environment (environment.d); the token never reaches git, the
// database or the logs (AGENTS.md §10 rule 3, AUD-110).
//
// Environment variables:
//
//	SCHOOL_HA_URL                base URL, for example http://192.168.20.30:8123
//	SCHOOL_HA_TOKEN              long-lived access token (secret)
//	SCHOOL_HA_CALENDAR_ENTITY    calendar entity id, for example calendar.school
//	SCHOOL_HA_INSECURE           true to skip TLS verification (internal CA)
//	SCHOOL_HA_TIMEOUT            per-request timeout, default 20s
//
// Calendar writing stays off until all three of URL, token and entity are set,
// so the service still starts before the calendar is configured.
type CalendarConfig struct {
	BaseURL  string
	Token    string
	EntityID string
	Insecure bool
	Timeout  time.Duration
}

// Enabled reports whether the calendar target is fully configured.
func (c CalendarConfig) Enabled() bool {
	return c.BaseURL != "" && c.Token != "" && c.EntityID != ""
}

// Missing lists the environment variables that are still unset, in the order
// the operator should set them. An empty result means the target is usable.
func (c CalendarConfig) Missing() []string {
	var out []string
	if c.BaseURL == "" {
		out = append(out, "SCHOOL_HA_URL")
	}
	if c.Token == "" {
		out = append(out, "SCHOOL_HA_TOKEN")
	}
	if c.EntityID == "" {
		out = append(out, "SCHOOL_HA_CALENDAR_ENTITY")
	}
	return out
}

// AppriseConfig points at the house Apprise API on `.35:8210` (AGENTS.md §8)
// and names the destinations by tag. The school service never holds an email
// address, a phone number or an SMTP password; the Apprise API holds those and
// selects them by tag (AGENTS.md §10 rule 3).
//
// Environment variables:
//
//	SCHOOL_APPRISE_URL       API base, default http://192.168.20.35:8210
//	SCHOOL_APPRISE_KEY       stored configuration key (required to send)
//	SCHOOL_APPRISE_TOKEN     optional bearer token
//	SCHOOL_APPRISE_TIMEOUT   per-request timeout, default 15s
//	SCHOOL_APPRISE_CHANNELS  channels to use, default "email,whatsapp"
//	SCHOOL_APPRISE_TAGS      recipient=tag-base list, default
//	                         "Harry=harry,Finn=finn,Jo=joanna,Sam=sam"
//	SCHOOL_APPRISE_PARENTS   who gets the combined brief, default "Jo,Sam"
//	SCHOOL_NOTIFY_TOKEN      bearer token for POST /notify/morning (n8n)
//
// A channel tag is the recipient's tag base plus "_email" or "_whatsapp",
// which is the naming the house Apprise configuration already uses.
type AppriseConfig struct {
	BaseURL string
	// Key names the stored Apprise configuration that holds every destination.
	Key string
	// Token is an optional bearer token when the Apprise API is protected.
	Token string
	// Timeout bounds one delivery attempt.
	Timeout time.Duration
	// Channels are the channels the morning brief uses, in order. Each entry is
	// "email" or "whatsapp".
	Channels []string
	// Recipients are the people a brief can be sent to, in order.
	Recipients []Recipient
	// Parents are the recipient names that receive the combined brief.
	Parents []string
	// NotifyToken guards POST /notify/morning, the endpoint n8n calls.
	NotifyToken string
}

// Recipient is one person a brief can go to. TagBase is the Apprise tag prefix,
// for example "harry" for the tags harry_email and harry_whatsapp.
type Recipient struct {
	Name    string
	TagBase string
}

// The channels Phase 7 delivers on (AGENTS.md §13 decision 8).
const (
	ChannelEmail    = "email"
	ChannelWhatsApp = "whatsapp"
)

// DefaultAppriseURL is the house Apprise API on `.35` (AGENTS.md §2a, §8).
const DefaultAppriseURL = "http://192.168.20.35:8210"

// DefaultAppriseTags is the recipient list already present in the house
// Apprise configuration: each boy, and both parents.
const DefaultAppriseTags = "Harry=harry,Finn=finn,Jo=joanna,Sam=sam"

// DefaultAppriseParents is who receives the combined brief (FR-14).
const DefaultAppriseParents = "Jo,Sam"

// Enabled reports whether a brief can be delivered at all.
func (c AppriseConfig) Enabled() bool {
	return c.BaseURL != "" && c.Key != ""
}

// Missing lists the environment variables that are still unset, in the order
// the operator should set them. An empty result means the gateway is usable.
func (c AppriseConfig) Missing() []string {
	var out []string
	if c.BaseURL == "" {
		out = append(out, "SCHOOL_APPRISE_URL")
	}
	if c.Key == "" {
		out = append(out, "SCHOOL_APPRISE_KEY")
	}
	return out
}

// RecipientByName returns the configured recipient with the given name.
func (c AppriseConfig) RecipientByName(name string) (Recipient, bool) {
	for _, r := range c.Recipients {
		if strings.EqualFold(r.Name, strings.TrimSpace(name)) {
			return r, true
		}
	}
	return Recipient{}, false
}

// ChannelTag is the Apprise tag for one recipient and channel, for example
// "harry_email".
func (c AppriseConfig) ChannelTag(r Recipient, channel string) string {
	return r.TagBase + "_" + strings.ToLower(strings.TrimSpace(channel))
}

// IsParent reports whether the recipient receives the combined brief.
func (c AppriseConfig) IsParent(name string) bool {
	for _, p := range c.Parents {
		if strings.EqualFold(strings.TrimSpace(p), strings.TrimSpace(name)) {
			return true
		}
	}
	return false
}

// ParentRecipients returns the configured parents, in order.
func (c AppriseConfig) ParentRecipients() []Recipient {
	out := make([]Recipient, 0, len(c.Parents))
	for _, name := range c.Parents {
		if r, ok := c.RecipientByName(name); ok {
			out = append(out, r)
		}
	}
	return out
}

// ValidChannels returns the requested channels that are configured, in order,
// and the ones that are not.
func (c AppriseConfig) ValidChannels() ([]string, []string) {
	var ok, bad []string
	for _, ch := range c.Channels {
		switch ch {
		case ChannelEmail, ChannelWhatsApp:
			ok = append(ok, ch)
		default:
			bad = append(bad, ch)
		}
	}
	return ok, bad
}

// DefaultTimezone is the family timezone used when SCHOOL_TIMEZONE is unset.
const DefaultTimezone = "Australia/Sydney"

// Load reads and validates the configuration.
func Load() (*Config, error) {
	cfg := &Config{
		Addr:              env("SCHOOL_ADDR", ":8792"),
		DBPath:            env("SCHOOL_DB_PATH", "/data/school.db"),
		AdminUsername:     env("SCHOOL_ADMIN_USERNAME", "sam"),
		AdminPassword:     os.Getenv("SCHOOL_ADMIN_PASSWORD"),
		AdminPasswordHash: os.Getenv("SCHOOL_ADMIN_PASSWORD_HASH"),
		CookieSecure:      envBool("SCHOOL_COOKIE_SECURE", true),
		AppEnv:            env("SCHOOL_APP_ENV", "production"),
	}

	secret := os.Getenv("SCHOOL_SESSION_SECRET")
	if len(secret) < 16 {
		return nil, errors.New("SCHOOL_SESSION_SECRET must be set and at least 16 characters")
	}
	cfg.SessionSecret = []byte(secret)

	if cfg.AdminPassword == "" && cfg.AdminPasswordHash == "" {
		return nil, errors.New("set SCHOOL_ADMIN_PASSWORD or SCHOOL_ADMIN_PASSWORD_HASH")
	}
	if cfg.AdminUsername == "" {
		return nil, errors.New("SCHOOL_ADMIN_USERNAME must not be empty")
	}

	ttl, err := time.ParseDuration(env("SCHOOL_SESSION_TTL", "12h"))
	if err != nil {
		return nil, fmt.Errorf("SCHOOL_SESSION_TTL: %w", err)
	}
	cfg.SessionTTL = ttl

	lvl, err := parseLevel(env("SCHOOL_LOG_LEVEL", "info"))
	if err != nil {
		return nil, err
	}
	cfg.LogLevel = lvl

	loc, err := time.LoadLocation(env("SCHOOL_TIMEZONE", DefaultTimezone))
	if err != nil {
		return nil, fmt.Errorf("SCHOOL_TIMEZONE: %w", err)
	}
	cfg.Location = loc
	cfg.Calendar = loadCalendar()
	cfg.HubToken = strings.TrimSpace(os.Getenv("SCHOOL_HUB_TOKEN"))
	apprise, err := loadApprise()
	if err != nil {
		return nil, err
	}
	cfg.Apprise = apprise

	return cfg, nil
}

// DBConfig is the minimum a database-only command needs. The parse subcommand
// opens the same SQLite file as the service without requiring the service's
// session secret or login.
type DBConfig struct {
	DBPath   string
	Location *time.Location
	Calendar CalendarConfig
	Apprise  AppriseConfig
}

// LoadDB reads the database path, the family timezone, the calendar target and
// the notification gateway only.
func LoadDB() (*DBConfig, error) {
	loc, err := time.LoadLocation(env("SCHOOL_TIMEZONE", DefaultTimezone))
	if err != nil {
		return nil, fmt.Errorf("SCHOOL_TIMEZONE: %w", err)
	}
	apprise, err := loadApprise()
	if err != nil {
		return nil, err
	}
	return &DBConfig{
		DBPath:   env("SCHOOL_DB_PATH", "/data/school.db"),
		Location: loc,
		Calendar: loadCalendar(),
		Apprise:  apprise,
	}, nil
}

// loadApprise reads the Apprise gateway settings. Like the calendar target it
// never fails on an empty value: the service boots before the gateway is
// configured, and every send then fails loudly instead of silently.
func loadApprise() (AppriseConfig, error) {
	c := AppriseConfig{
		BaseURL:     strings.TrimRight(env("SCHOOL_APPRISE_URL", DefaultAppriseURL), "/"),
		Key:         strings.TrimSpace(os.Getenv("SCHOOL_APPRISE_KEY")),
		Token:       strings.TrimSpace(os.Getenv("SCHOOL_APPRISE_TOKEN")),
		Timeout:     15 * time.Second,
		Channels:    splitList(env("SCHOOL_APPRISE_CHANNELS", ChannelEmail+","+ChannelWhatsApp)),
		Parents:     splitList(env("SCHOOL_APPRISE_PARENTS", DefaultAppriseParents)),
		NotifyToken: strings.TrimSpace(os.Getenv("SCHOOL_NOTIFY_TOKEN")),
	}
	if v := strings.TrimSpace(os.Getenv("SCHOOL_APPRISE_TIMEOUT")); v != "" {
		if d, err := time.ParseDuration(v); err == nil && d > 0 {
			c.Timeout = d
		}
	}

	recipients, err := parseRecipients(env("SCHOOL_APPRISE_TAGS", DefaultAppriseTags))
	if err != nil {
		return c, fmt.Errorf("SCHOOL_APPRISE_TAGS: %w", err)
	}
	c.Recipients = recipients

	for _, p := range c.Parents {
		if _, ok := c.RecipientByName(p); !ok {
			return c, fmt.Errorf("SCHOOL_APPRISE_PARENTS: %q is not in SCHOOL_APPRISE_TAGS", p)
		}
	}
	if _, bad := c.ValidChannels(); len(bad) > 0 {
		return c, fmt.Errorf("SCHOOL_APPRISE_CHANNELS: unknown channel(s) %s", strings.Join(bad, ", "))
	}
	return c, nil
}

// parseRecipients reads the "Name=tagbase,Name=tagbase" recipient list. The tag
// base names the Apprise destinations, so a name that is wrong fails at send
// time with the Apprise error, not here.
func parseRecipients(v string) ([]Recipient, error) {
	var out []Recipient
	for _, entry := range splitList(v) {
		name, tag, found := strings.Cut(entry, "=")
		name = strings.TrimSpace(name)
		tag = strings.TrimSpace(tag)
		if !found || name == "" || tag == "" {
			return nil, fmt.Errorf("expected Name=tag entries, got %q", entry)
		}
		out = append(out, Recipient{Name: name, TagBase: tag})
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("no recipients configured")
	}
	return out, nil
}

// splitList splits a comma list and drops empty entries.
func splitList(v string) []string {
	var out []string
	for _, part := range strings.Split(v, ",") {
		if p := strings.TrimSpace(part); p != "" {
			out = append(out, p)
		}
	}
	return out
}

// loadCalendar reads the Home Assistant calendar target. It never fails: an
// empty value simply leaves the target disabled, so the service boots before
// the calendar is configured and the calendar commands fail loudly instead.
func loadCalendar() CalendarConfig {
	timeout := 20 * time.Second
	if v := strings.TrimSpace(os.Getenv("SCHOOL_HA_TIMEOUT")); v != "" {
		if d, err := time.ParseDuration(v); err == nil && d > 0 {
			timeout = d
		}
	}
	return CalendarConfig{
		BaseURL:  strings.TrimRight(strings.TrimSpace(os.Getenv("SCHOOL_HA_URL")), "/"),
		Token:    strings.TrimSpace(os.Getenv("SCHOOL_HA_TOKEN")),
		EntityID: strings.TrimSpace(os.Getenv("SCHOOL_HA_CALENDAR_ENTITY")),
		Insecure: envBool("SCHOOL_HA_INSECURE", false),
		Timeout:  timeout,
	}
}

func env(key, fallback string) string {
	if v := strings.TrimSpace(os.Getenv(key)); v != "" {
		return v
	}
	return fallback
}

func envBool(key string, fallback bool) bool {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return fallback
	}
	b, err := strconv.ParseBool(v)
	if err != nil {
		return fallback
	}
	return b
}

func parseLevel(s string) (slog.Level, error) {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "debug":
		return slog.LevelDebug, nil
	case "info", "":
		return slog.LevelInfo, nil
	case "warn", "warning":
		return slog.LevelWarn, nil
	case "error":
		return slog.LevelError, nil
	default:
		return 0, fmt.Errorf("SCHOOL_LOG_LEVEL: unknown level %q", s)
	}
}