package service

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"path"
	"strings"
	"time"

	"github.com/prabhupadasays/spsays-bff/internal/model"
	"github.com/prabhupadasays/spsays-bff/internal/repository"
)

// UserService handles profile-edit + avatar-upload flows.
type UserService struct {
	users *repository.UserRepo
	r2    *repository.R2
}

func NewUserService(users *repository.UserRepo, r2 *repository.R2) *UserService {
	return &UserService{users: users, r2: r2}
}

// UpdateProfile updates the user's name, avatar URL, and/or handle.
//
// `avatarURL` semantics:
//
//	nil  → don't touch
//	""   → clear (remove avatar)
//	"x"  → set to "x"
//
// `handle` is normalized to the project's slug format before being passed
// to the DB so users can't sneak in spaces or punctuation. Empty after
// normalization → 400.
// UpdateProfileInput is the partial profile patch a handler hands the
// service. Every field is a pointer so nil means "leave unchanged". The
// service validates/normalizes each present field, then maps to a
// repository.ProfileUpdate.
type UpdateProfileInput struct {
	Name                  *string
	AvatarURL             *string
	Handle                *string
	Country               *string
	Sampradaya            *string
	Gender                *string
	Initiated             *bool
	InitiatedAt           *string
	DailyChantingRounds   *int
	PreferredChantingTime *string
	PeakActiveTime        *string
}

// validGenders is the accepted set; "" clears the field.
var validGenders = map[string]bool{"male": true, "female": true, "other": true}

// validSampradayas is the accepted lineage set. Currently just Gaudiya
// (the default); add codes here as more lineages are supported.
var validSampradayas = map[string]bool{"gaudiya": true}

func (s *UserService) UpdateProfile(ctx context.Context, id string, in UpdateProfileInput) (*model.User, error) {
	p := repository.ProfileUpdate{
		AvatarURL:           in.AvatarURL, // passthrough: nil=leave, ""=clear, x=set
		Initiated:           in.Initiated,
		DailyChantingRounds: in.DailyChantingRounds,
	}

	if in.Name != nil {
		trimmed := strings.TrimSpace(*in.Name)
		if trimmed == "" {
			return nil, errors.New("name cannot be empty")
		}
		if len(trimmed) > 120 {
			return nil, errors.New("name too long (max 120)")
		}
		p.Name = &trimmed
	}
	if in.Handle != nil {
		clean := normalizeHandle(*in.Handle)
		if len(clean) < 3 {
			return nil, errors.New("handle must be at least 3 characters (letters, digits, dashes)")
		}
		if len(clean) > 32 {
			return nil, errors.New("handle too long (max 32)")
		}
		p.Handle = &clean
	}
	if in.Country != nil {
		// "" clears; otherwise a 2-letter ISO-3166-1 alpha-2 code (the
		// frontend dropdown only ever sends valid codes).
		cc := strings.ToUpper(strings.TrimSpace(*in.Country))
		if cc != "" && len(cc) != 2 {
			return nil, errors.New("country must be a 2-letter code")
		}
		p.Country = &cc
	}
	if in.Sampradaya != nil {
		// "" clears (optional field); otherwise must be a known lineage.
		s := strings.ToLower(strings.TrimSpace(*in.Sampradaya))
		if s != "" && !validSampradayas[s] {
			return nil, errors.New("unknown sampradaya")
		}
		p.Sampradaya = &s
	}
	if in.Gender != nil {
		g := strings.ToLower(strings.TrimSpace(*in.Gender))
		if g != "" && !validGenders[g] {
			return nil, errors.New("gender must be male, female, or other")
		}
		p.Gender = &g
	}
	if in.InitiatedAt != nil {
		d := strings.TrimSpace(*in.InitiatedAt)
		if d != "" {
			if _, err := time.Parse("2006-01-02", d); err != nil {
				return nil, errors.New("initiated_at must be a date (YYYY-MM-DD)")
			}
		}
		p.InitiatedAt = &d
	}
	if in.DailyChantingRounds != nil {
		// 0 is the clear sentinel; real values are 1–1008 (DB enforces too).
		n := *in.DailyChantingRounds
		if n != 0 && (n < 1 || n > 1008) {
			return nil, errors.New("daily_chanting_rounds must be between 1 and 1008")
		}
	}
	if in.PreferredChantingTime != nil {
		t, err := normalizeClock(*in.PreferredChantingTime)
		if err != nil {
			return nil, errors.New("preferred_chanting_time must be HH:MM")
		}
		p.PreferredChantingTime = &t
	}
	if in.PeakActiveTime != nil {
		t, err := normalizeClock(*in.PeakActiveTime)
		if err != nil {
			return nil, errors.New("peak_active_time must be HH:MM")
		}
		p.PeakActiveTime = &t
	}

	return s.users.UpdateProfile(ctx, id, p)
}

// normalizeClock validates an "HH:MM" 24-hour clock time, returning "" for
// a blank input (clear). The system-managed notification fields use this.
func normalizeClock(raw string) (string, error) {
	t := strings.TrimSpace(raw)
	if t == "" {
		return "", nil
	}
	if _, err := time.Parse("15:04", t); err != nil {
		return "", err
	}
	return t, nil
}

// Search returns users matching the query (handle or name substring).
// Used by the public user-search endpoint on the /search page.
func (s *UserService) Search(ctx context.Context, q string, limit int) ([]model.User, error) {
	return s.users.Search(ctx, q, limit)
}

// GetReadingPrefs returns the user's reading prefs blob (opaque JSON).
// Used by the frontend to hydrate ReadingSettings on sign-in so the
// theme/palette/font choices roam across devices.
func (s *UserService) GetReadingPrefs(ctx context.Context, id string) ([]byte, error) {
	return s.users.GetReadingPrefs(ctx, id)
}

// UpdateReadingPrefs overwrites the user's reading prefs blob. The
// handler re-marshals the decoded request before calling in here so we
// know `prefsJSON` is well-formed by the time it hits the DB.
func (s *UserService) UpdateReadingPrefs(ctx context.Context, id string, prefsJSON []byte) error {
	return s.users.UpdateReadingPrefs(ctx, id, prefsJSON)
}

// normalizeHandle lowercases and strips anything that isn't [a-z0-9-]. Same
// rules as slugForHandle in auth_service, but exposed here because the
// profile-update path doesn't go through auth.
func normalizeHandle(raw string) string {
	var b strings.Builder
	for _, r := range strings.ToLower(strings.TrimSpace(raw)) {
		switch {
		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
			b.WriteRune(r)
		case r == '-', r == '.', r == '_':
			b.WriteByte('-')
		}
	}
	out := strings.Trim(b.String(), "-")
	// Collapse runs of dashes.
	for strings.Contains(out, "--") {
		out = strings.ReplaceAll(out, "--", "-")
	}
	return out
}

// AvatarPresign issues a one-shot presigned PUT URL the frontend uses to
// upload an avatar directly to R2.
//
// The key is namespaced under `avatars/<user_id>/<random>.<ext>` so:
//   - we can list / clean up a user's avatars with one prefix scan
//   - the random suffix forces cache invalidation when the avatar changes
//   - a malicious user can't overwrite someone else's avatar (their JWT
//     scopes the user_id portion of the key)
//
// Returns (uploadURL, publicURL, error). The frontend then PUTs to uploadURL
// and POSTs publicURL back as the new avatar.
func (s *UserService) AvatarPresign(ctx context.Context, userID, contentType string) (uploadURL, publicURL string, err error) {
	if s.r2 == nil {
		return "", "", errors.New("avatar uploads are not configured")
	}
	ext, ok := extensionFor(contentType)
	if !ok {
		return "", "", fmt.Errorf("unsupported content type: %s", contentType)
	}

	suffix := make([]byte, 8)
	if _, err := rand.Read(suffix); err != nil {
		return "", "", err
	}
	key := path.Join("avatars", userID, hex.EncodeToString(suffix)+ext)

	return s.r2.PresignPut(ctx, key, contentType, 5*time.Minute)
}

// extensionFor whitelists the image content types we accept. Restricting
// here is the cheap-but-effective defence against users uploading arbitrary
// binaries to our R2 bucket.
func extensionFor(ct string) (string, bool) {
	switch ct {
	case "image/png":
		return ".png", true
	case "image/jpeg":
		return ".jpg", true
	case "image/webp":
		return ".webp", true
	case "image/gif":
		return ".gif", true
	default:
		return "", false
	}
}