package mail

import (
	"errors"
	"fmt"
	"log"
	"strings"
)

// ErrNotConfigured is returned when a send is required but SMTP is not
// admin-configured (and no env fallback is available).
var ErrNotConfigured = errors.New("mail: SMTP is not configured; set platform mail settings in admin")

// ResolveFunc loads current SMTP config (typically from platformsettings).
// Callers must not log the returned password.
type ResolveFunc func() (Config, error)

// NewDynamic returns a Mailer that resolves SMTP config on each Send/Enabled.
// Prefer this over New(cfg) so admin dashboard changes apply without restart.
// When disabled or host empty, Send matches the historical no-op (log + nil)
// so invite re-issue can still mint tokens; callers that need hard failure
// should check Enabled() or use RequireConfigured.
func NewDynamic(resolve ResolveFunc) Mailer {
	if resolve == nil {
		return &noopMailer{}
	}
	return &dynamicMailer{resolve: resolve}
}

type dynamicMailer struct {
	resolve ResolveFunc
}

func (d *dynamicMailer) load() (Config, error) {
	cfg, err := d.resolve()
	if err != nil {
		return Config{}, err
	}
	if strings.TrimSpace(cfg.Port) == "" {
		cfg.Port = "587"
	}
	return cfg, nil
}

func (d *dynamicMailer) Enabled() bool {
	cfg, err := d.load()
	if err != nil {
		return false
	}
	return cfg.Enabled && strings.TrimSpace(cfg.Host) != ""
}

func (d *dynamicMailer) Send(msg Message) error {
	cfg, err := d.load()
	if err != nil {
		log.Printf("mail: config resolve failed subject=%q", msg.Subject)
		return fmt.Errorf("%w: %v", ErrNotConfigured, err)
	}
	if !cfg.Enabled || strings.TrimSpace(cfg.Host) == "" {
		return (&noopMailer{}).Send(msg)
	}
	return (&smtpMailer{cfg: cfg}).Send(msg)
}

// RequireConfigured wraps a Mailer so Send fails clearly when delivery is off.
func RequireConfigured(inner Mailer) Mailer {
	if inner == nil {
		return &requireConfiguredMailer{inner: &noopMailer{}}
	}
	return &requireConfiguredMailer{inner: inner}
}

type requireConfiguredMailer struct {
	inner Mailer
}

func (r *requireConfiguredMailer) Enabled() bool { return r.inner.Enabled() }

func (r *requireConfiguredMailer) Send(msg Message) error {
	if !r.inner.Enabled() {
		return ErrNotConfigured
	}
	return r.inner.Send(msg)
}

// ConfigFromParts builds a Config from discrete fields (platformsettings bridge).
func ConfigFromParts(enabled bool, host, port, user, password, from string) Config {
	if strings.TrimSpace(port) == "" {
		port = "587"
	}
	return Config{
		Enabled:  enabled,
		Host:     strings.TrimSpace(host),
		Port:     strings.TrimSpace(port),
		User:     strings.TrimSpace(user),
		Password: password,
		From:     strings.TrimSpace(from),
	}
}

// ApplyDryRun forces Enabled=false when dry-run is on so New/NewDynamic use the
// noop path (log subject only). Host/from are preserved for diagnostics.
func ApplyDryRun(dryRun bool, cfg Config) Config {
	if dryRun {
		cfg.Enabled = false
	}
	return cfg
}