package email

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/descrybe/descrybe-v2/apps/api/internal/platformsettings"
	"github.com/descrybe/descrybe-v2/apps/api/internal/security"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// EnvConfig holds process-level email defaults (platform fallback / dry-run).
type EnvConfig struct {
	AppEncryptionKey         string
	CredentialsEncryptionKey string
	TokenSigningSecret       string
	DatabaseURL              string
	PublicAPIURL             string
	WebOrigin                string
	EmailDryRun              bool
	ResendAPIKey             string
	SMTPHost                 string
	SMTPPort                 string
	SMTPUser                 string
	SMTPPassword             string
	SMTPFrom                 string
	SendRPM                  int
	SendRPH                  int
}

type Service struct {
	Pool       *pgxpool.Pool
	Key        []byte
	Env        EnvConfig
	HTTPClient *http.Client
	rpm        *slidingLimiter
	rph        *slidingLimiter
	// Platform is optional; when set, Resend/SMTP/dry-run prefer admin settings over Env.
	Platform *platformsettings.Service
}

func NewService(pool *pgxpool.Pool, env EnvConfig) *Service {
	keyMaterial := firstNonEmpty(env.AppEncryptionKey, env.CredentialsEncryptionKey, env.TokenSigningSecret)
	rpm := env.SendRPM
	if rpm <= 0 {
		rpm = 30
	}
	rph := env.SendRPH
	if rph <= 0 {
		rph = 500
	}
	return &Service{
		Pool: pool,
		Key:  DeriveKey(keyMaterial, env.DatabaseURL),
		Env:  env,
		HTTPClient: &http.Client{
			Timeout: 20 * time.Second,
		},
		rpm: newSlidingLimiter(rpm, time.Minute),
		rph: newSlidingLimiter(rph, time.Hour),
	}
}

type providerSecrets struct {
	APIKey       string `json:"api_key,omitempty"`
	SMTPHost     string `json:"smtp_host,omitempty"`
	SMTPPort     string `json:"smtp_port,omitempty"`
	SMTPUser     string `json:"smtp_user,omitempty"`
	SMTPPassword string `json:"smtp_password,omitempty"`
}

type providerConfigJSON struct {
	Domain  string `json:"domain,omitempty"`
	ReplyTo string `json:"reply_to,omitempty"`
}

type storedProvider struct {
	id, providerType, fromEmail, fromName, secretsEnc string
	config                                            []byte
	status                                            string
	verifiedAt, createdAt, updatedAt                  time.Time
	verifiedAtPtr                                     *time.Time
	lastError                                         *string
}

func (s *Service) loadStored(ctx context.Context, companyID uuid.UUID) (storedProvider, error) {
	var sp storedProvider
	var verifiedAt *time.Time
	err := s.Pool.QueryRow(ctx, `
		SELECT id::text, provider_type, from_email, from_name, secrets_enc, config, status,
		       verified_at, last_error, created_at, updated_at
		FROM email_providers WHERE company_id = $1`, companyID).Scan(
		&sp.id, &sp.providerType, &sp.fromEmail, &sp.fromName, &sp.secretsEnc, &sp.config, &sp.status,
		&verifiedAt, &sp.lastError, &sp.createdAt, &sp.updatedAt,
	)
	sp.verifiedAtPtr = verifiedAt
	if verifiedAt != nil {
		sp.verifiedAt = *verifiedAt
	}
	return sp, err
}

func (s *Service) decryptSecrets(enc string) (providerSecrets, error) {
	var out providerSecrets
	if enc == "" {
		return out, nil
	}
	plain, err := DecryptSecret(s.Key, enc)
	if err != nil {
		return out, err
	}
	if plain == "" {
		return out, nil
	}
	if err := json.Unmarshal([]byte(plain), &out); err != nil {
		return out, err
	}
	return out, nil
}

func (s *Service) parseConfig(raw []byte) providerConfigJSON {
	var c providerConfigJSON
	_ = json.Unmarshal(raw, &c)
	return c
}

func (s *Service) dryRunState(ctx context.Context, companyID uuid.UUID) (bool, string) {
	if s.Platform != nil {
		if resolved, err := s.Platform.ResolveEmailDryRun(ctx); err == nil {
			if resolved.DryRun {
				if resolved.Source == platformsettings.SourceDB {
					return true, "platform_settings.email_dry_run"
				}
				if resolved.Source == platformsettings.SourceEnv {
					return true, "EMAIL_DRY_RUN=true"
				}
				return true, "email_dry_run_default"
			}
			// explicitly false from settings/env — continue to free-plan check
		} else if s.Env.EmailDryRun {
			return true, "EMAIL_DRY_RUN=true"
		}
	} else if s.Env.EmailDryRun {
		return true, "EMAIL_DRY_RUN=true"
	}
	if s.isFreePlan(ctx, companyID) {
		return true, "free_plan"
	}
	return false, ""
}

func (s *Service) platformResendKey(ctx context.Context) string {
	if s.Platform != nil {
		if resolved, err := s.Platform.ResolveResend(ctx); err == nil && strings.TrimSpace(resolved.APIKey) != "" {
			return strings.TrimSpace(resolved.APIKey)
		}
	}
	return strings.TrimSpace(s.Env.ResendAPIKey)
}

func (s *Service) platformSMTP(ctx context.Context) (host, port, user, pass string) {
	if s.Platform != nil {
		if resolved, err := s.Platform.ResolveSMTP(ctx); err == nil {
			return resolved.Host, resolved.Port, resolved.User, resolved.Password
		}
	}
	return strings.TrimSpace(s.Env.SMTPHost), strings.TrimSpace(s.Env.SMTPPort),
		strings.TrimSpace(s.Env.SMTPUser), s.Env.SMTPPassword
}

func (s *Service) isFreePlan(ctx context.Context, companyID uuid.UUID) bool {
	var name string
	err := s.Pool.QueryRow(ctx, `
		SELECT LOWER(p.name)
		FROM company_plans cp
		JOIN plans p ON p.id = cp.plan_id
		WHERE cp.company_id = $1 AND cp.is_active = true
		ORDER BY cp.updated_at DESC
		LIMIT 1`, companyID).Scan(&name)
	if err != nil {
		return false
	}
	return name == "free" || strings.HasPrefix(name, "free ")
}

func (s *Service) GetConfig(ctx context.Context, companyID uuid.UUID) (PublicConfig, error) {
	dry, reason := s.dryRunState(ctx, companyID)
	sp, err := s.loadStored(ctx, companyID)
	if errors.Is(err, pgx.ErrNoRows) {
		hint := ""
		if s.platformResendKey(ctx) != "" {
			hint = ProviderResend
		} else if host, _, _, _ := s.platformSMTP(ctx); host != "" {
			hint = ProviderSMTP
		}
		return PublicConfig{
			Provider:        ProviderSMTP,
			Configured:      false,
			DryRunForced:    dry,
			DryRunReason:    reason,
			CanSendReal:     false,
			EnvProviderHint: hint,
		}, nil
	}
	if err != nil {
		return PublicConfig{}, err
	}
	secrets, _ := s.decryptSecrets(sp.secretsEnc)
	cfg := s.parseConfig(sp.config)
	domain := cfg.Domain
	if domain == "" {
		domain = domainOfEmail(sp.fromEmail)
	}
	verified := sp.status == "verified"
	_, _, _, platPass := s.platformSMTP(ctx)
	return PublicConfig{
		Provider:        sp.providerType,
		FromEmail:       sp.fromEmail,
		FromName:        sp.fromName,
		ReplyTo:         cfg.ReplyTo,
		Domain:          domain,
		SMTPHost:        secrets.SMTPHost,
		SMTPPort:        secrets.SMTPPort,
		SMTPUser:        secrets.SMTPUser,
		IsEnabled:       sp.status != "error",
		Configured:      true,
		DomainVerified:  verified,
		FromVerified:    verified,
		Verified:        verified,
		VerifiedAt:      sp.verifiedAtPtr,
		HasAPIKey:       secrets.APIKey != "" || s.platformResendKey(ctx) != "",
		HasSMTPPassword: secrets.SMTPPassword != "" || platPass != "",
		LastTestStatus:  statusPtr(sp.status),
		DryRunForced:    dry,
		DryRunReason:    reason,
		CanSendReal:     verified && !dry,
	}, nil
}

func statusPtr(s string) *string { return &s }

func (s *Service) UpdateConfig(ctx context.Context, companyID uuid.UUID, in UpdateInput) (PublicConfig, error) {
	provider := strings.ToLower(strings.TrimSpace(in.Provider))
	if provider == "" {
		provider = ProviderSMTP
	}
	if provider != ProviderResend && provider != ProviderSMTP {
		return PublicConfig{}, ClientMsg("provider must be resend or smtp")
	}
	fromEmail, err := parseAddress(in.FromEmail)
	if err != nil && strings.TrimSpace(in.FromEmail) != "" {
		return PublicConfig{}, err
	}
	domain := strings.ToLower(strings.TrimSpace(in.Domain))
	if domain == "" && fromEmail != "" {
		domain = domainOfEmail(fromEmail)
	}
	if fromEmail != "" && domain != "" && domainOfEmail(fromEmail) != domain {
		return PublicConfig{}, ClientMsg("from_email domain must match domain field")
	}

	var secrets providerSecrets
	existing, err := s.loadStored(ctx, companyID)
	if err == nil {
		secrets, _ = s.decryptSecrets(existing.secretsEnc)
	} else if !errors.Is(err, pgx.ErrNoRows) {
		return PublicConfig{}, err
	}

	if strings.TrimSpace(in.APIKey) != "" {
		secrets.APIKey = strings.TrimSpace(in.APIKey)
	}
	if strings.TrimSpace(in.SMTPHost) != "" {
		host := strings.TrimSpace(in.SMTPHost)
		if err := security.AssertDialableSMTPHost(ctx, host); err != nil {
			return PublicConfig{}, ErrSMTPHostBlocked
		}
		secrets.SMTPHost = host
	}
	if strings.TrimSpace(in.SMTPPort) != "" {
		secrets.SMTPPort = strings.TrimSpace(in.SMTPPort)
	} else if secrets.SMTPPort == "" {
		secrets.SMTPPort = "587"
	}
	if strings.TrimSpace(in.SMTPUser) != "" {
		secrets.SMTPUser = strings.TrimSpace(in.SMTPUser)
	}
	if strings.TrimSpace(in.SMTPPassword) != "" {
		secrets.SMTPPassword = strings.TrimSpace(in.SMTPPassword)
	}

	secBytes, err := json.Marshal(secrets)
	if err != nil {
		return PublicConfig{}, err
	}
	enc, err := EncryptSecret(s.Key, string(secBytes))
	if err != nil {
		return PublicConfig{}, err
	}
	cfgBytes, err := json.Marshal(providerConfigJSON{
		Domain:  domain,
		ReplyTo: strings.TrimSpace(in.ReplyTo),
	})
	if err != nil {
		return PublicConfig{}, err
	}

	_, err = s.Pool.Exec(ctx, `
		INSERT INTO email_providers (company_id, provider_type, from_email, from_name, secrets_enc, config, status)
		VALUES ($1,$2,$3,$4,$5,$6::jsonb,'unverified')
		ON CONFLICT (company_id) DO UPDATE SET
			provider_type = EXCLUDED.provider_type,
			from_email = EXCLUDED.from_email,
			from_name = EXCLUDED.from_name,
			secrets_enc = EXCLUDED.secrets_enc,
			config = EXCLUDED.config,
			status = 'unverified',
			verified_at = NULL,
			last_error = NULL,
			updated_at = now()`,
		companyID, provider, fromEmail, strings.TrimSpace(in.FromName), enc, string(cfgBytes),
	)
	if err != nil {
		return PublicConfig{}, err
	}
	return s.GetConfig(ctx, companyID)
}

func (s *Service) transportFor(sp storedProvider, secrets providerSecrets) (Transport, FromIdentity, error) {
	fromEmail := strings.TrimSpace(sp.fromEmail)
	if fromEmail == "" {
		return nil, FromIdentity{}, ErrInvalidFrom
	}
	cfg := s.parseConfig(sp.config)
	from := FromIdentity{Email: fromEmail, Name: sp.fromName, ReplyTo: cfg.ReplyTo}
	switch sp.providerType {
	case ProviderResend:
		apiKey := secrets.APIKey
		if apiKey == "" {
			apiKey = s.platformResendKey(context.Background())
		}
		if apiKey == "" {
			return nil, from, ErrProviderMisconfig
		}
		return newResendTransport(apiKey, s.HTTPClient), from, nil
	case ProviderSMTP:
		host := secrets.SMTPHost
		user := secrets.SMTPUser
		pass := secrets.SMTPPassword
		port := secrets.SMTPPort
		if host == "" || user == "" || pass == "" || port == "" {
			ph, pp, pu, pw := s.platformSMTP(context.Background())
			if host == "" {
				host = ph
			}
			if user == "" {
				user = pu
			}
			if pass == "" {
				pass = pw
			}
			if port == "" {
				port = pp
			}
		}
		if host == "" {
			return nil, from, ErrProviderMisconfig
		}
		if err := security.AssertDialableSMTPHost(context.Background(), host); err != nil {
			return nil, from, ErrSMTPHostBlocked
		}
		return newSMTPTransport(host, port, user, pass), from, nil
	default:
		return nil, from, ErrProviderMisconfig
	}
}

func (s *Service) VerifyDomain(ctx context.Context, companyID uuid.UUID) (PublicConfig, string, error) {
	sp, err := s.loadStored(ctx, companyID)
	if errors.Is(err, pgx.ErrNoRows) {
		return PublicConfig{}, "", ErrNotConfigured
	}
	if err != nil {
		return PublicConfig{}, "", err
	}
	secrets, err := s.decryptSecrets(sp.secretsEnc)
	if err != nil {
		return PublicConfig{}, "", err
	}
	cfg := s.parseConfig(sp.config)
	domain := cfg.Domain
	if domain == "" {
		domain = domainOfEmail(sp.fromEmail)
	}
	if sp.fromEmail == "" || domain == "" {
		return PublicConfig{}, "", ClientMsg("from_email and domain are required")
	}
	if domainOfEmail(sp.fromEmail) != strings.ToLower(domain) {
		return PublicConfig{}, "", ClientMsg(fmt.Sprintf("from_email must use domain %s", domain))
	}

	msg := "from address matches domain"
	ok := true
	if sp.providerType == ProviderResend {
		apiKey := secrets.APIKey
		if apiKey == "" {
			apiKey = s.platformResendKey(ctx)
		}
		if apiKey == "" {
			return PublicConfig{}, "", ErrProviderMisconfig
		}
		var detail string
		ok, detail, err = verifyResendDomain(ctx, apiKey, domain, s.HTTPClient)
		if err != nil {
			return PublicConfig{}, "", err
		}
		msg = detail
	} else {
		msg = "SMTP domain matched — send a test email to mark verified"
		ok = false // require successful test for SMTP
	}

	if ok {
		_, err = s.Pool.Exec(ctx, `
			UPDATE email_providers SET status='verified', verified_at=now(), last_error=NULL, updated_at=now()
			WHERE company_id=$1`, companyID)
	} else if sp.providerType == ProviderResend {
		_, err = s.Pool.Exec(ctx, `
			UPDATE email_providers SET status='error', last_error=$2, updated_at=now()
			WHERE company_id=$1`, companyID, msg)
	}
	if err != nil {
		return PublicConfig{}, "", err
	}
	out, err := s.GetConfig(ctx, companyID)
	return out, msg, err
}

func (s *Service) markVerified(ctx context.Context, companyID uuid.UUID) error {
	_, err := s.Pool.Exec(ctx, `
		UPDATE email_providers SET status='verified', verified_at=now(), last_error=NULL, updated_at=now()
		WHERE company_id=$1`, companyID)
	return err
}

func (s *Service) allowSend(companyID uuid.UUID) bool {
	key := companyID.String()
	return s.rpm.allow(key) && s.rph.allow(key)
}

func hashEmail(email string) string {
	sum := sha256.Sum256([]byte(normalizeEmail(email)))
	return hex.EncodeToString(sum[:])
}

// Send delivers test or blast emails. Blasts require confirm_understood == "I understand".
func (s *Service) Send(ctx context.Context, companyID uuid.UUID, req SendRequest) (SendResult, error) {
	mode := strings.ToLower(strings.TrimSpace(req.Mode))
	if mode == "" {
		mode = "test"
	}
	if mode != "test" && mode != "blast" {
		return SendResult{}, ClientMsg("mode must be test or blast")
	}
	if mode == "blast" && strings.TrimSpace(req.ConfirmUnderstood) != ConfirmUnderstoodPhrase {
		return SendResult{}, ErrMissingConfirm
	}
	if len(req.To) == 0 {
		return SendResult{}, ErrInvalidRecipient
	}
	if len(req.To) > 100 {
		return SendResult{}, ClientMsg("max 100 recipients per request")
	}
	if !s.allowSend(companyID) {
		return SendResult{}, ErrRateLimited
	}

	sp, err := s.loadStored(ctx, companyID)
	if errors.Is(err, pgx.ErrNoRows) {
		return SendResult{}, ErrNotConfigured
	}
	if err != nil {
		return SendResult{}, err
	}

	dry, reason := s.dryRunState(ctx, companyID)
	if req.ForceDryRun {
		dry = true
		if reason == "" {
			reason = "force_dry_run"
		}
	}

	if mode == "blast" && !dry && sp.status != "verified" {
		return SendResult{}, ErrNotVerified
	}

	secrets, err := s.decryptSecrets(sp.secretsEnc)
	if err != nil {
		return SendResult{}, err
	}
	transport, from, err := s.transportFor(sp, secrets)
	if err != nil {
		return SendResult{}, err
	}

	var campaignID *uuid.UUID
	if req.CampaignID != nil && strings.TrimSpace(*req.CampaignID) != "" {
		id, err := uuid.Parse(strings.TrimSpace(*req.CampaignID))
		if err != nil {
			return SendResult{}, ClientMsg("invalid campaign_id")
		}
		campaignID = &id
	}

	kind := mode
	if kind != "test" {
		kind = "blast"
	}

	out := SendResult{DryRun: dry, Reason: reason, Results: make([]RecipientResult, 0, len(req.To))}
	for _, rawTo := range req.To {
		to, err := parseAddress(rawTo)
		if err != nil {
			out.Failed++
			out.Results = append(out.Results, RecipientResult{Status: StatusFailed, Error: "invalid recipient"})
			continue
		}
		unsub, err := s.IsUnsubscribed(ctx, companyID, to)
		if err != nil {
			return out, err
		}
		if unsub {
			_ = s.logSend(ctx, companyID, campaignID, to, req.Subject, "unsubscribed", dry, kind, transport.Name(), "unsubscribed")
			out.Skipped++
			out.Results = append(out.Results, RecipientResult{Status: StatusSkippedUnsub})
			continue
		}

		_, pageURL, apiURL, err := s.ensureUnsubscribeToken(ctx, companyID, to)
		if err != nil {
			return out, err
		}
		html, text := injectUnsubscribeFooter(security.SanitizeEmailHTML(req.HTML), req.Text, pageURL)
		html = security.SanitizeEmailHTML(html)
		headers := listUnsubscribeHeaders(apiURL, "")

		if dry {
			log.Printf("email: dry-run company=%s provider=%s subject=%q", companyID, transport.Name(), req.Subject)
			_ = s.logSend(ctx, companyID, campaignID, to, req.Subject, "skipped", true, kind, transport.Name(), reason)
			out.Sent++
			out.Results = append(out.Results, RecipientResult{Status: StatusDryRun})
			continue
		}

		msg := Outbound{To: to, Subject: req.Subject, Text: text, HTML: html, Headers: headers}
		if err := transport.Send(ctx, from, msg); err != nil {
			log.Printf("email: send failed company=%s provider=%s", companyID, transport.Name())
			_ = s.logSend(ctx, companyID, campaignID, to, req.Subject, "failed", false, kind, transport.Name(), "send failed")
			out.Failed++
			out.Results = append(out.Results, RecipientResult{Status: StatusFailed, Error: "send failed"})
			continue
		}
		_ = s.logSend(ctx, companyID, campaignID, to, req.Subject, "sent", false, kind, transport.Name(), "")
		if mode == "test" {
			_ = s.markVerified(ctx, companyID)
		}
		out.Sent++
		out.Results = append(out.Results, RecipientResult{Status: StatusSent})
	}
	return out, nil
}

func (s *Service) logSend(ctx context.Context, companyID uuid.UUID, campaignID *uuid.UUID, to, subject, status string, dry bool, kind, provider, errMsg string) error {
	// 011 schema: recipient_email, recipient_hash, kind, status — dry-run stored as skipped + error note.
	st := status
	if dry && st != "unsubscribed" {
		st = "skipped"
	}
	_, err := s.Pool.Exec(ctx, `
		INSERT INTO email_sends (company_id, campaign_id, recipient_email, recipient_hash, kind, status, error, sent_at)
		VALUES ($1,$2,$3,$4,$5,$6,$7, CASE WHEN $6 = 'sent' THEN now() ELSE NULL END)`,
		companyID, campaignID, to, hashEmail(to), kind, st, nullIfEmpty(errMsg))
	_ = subject
	_ = provider
	return err
}

func nullIfEmpty(s string) *string {
	if strings.TrimSpace(s) == "" {
		return nil
	}
	return &s
}

func firstNonEmpty(vals ...string) string {
	for _, v := range vals {
		if strings.TrimSpace(v) != "" {
			return v
		}
	}
	return ""
}