package repository

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/prabhupadasays/spsays-bff/internal/model"
)

// ErrUserNotFound is returned by lookup methods when no row matches.
var ErrUserNotFound = errors.New("user not found")

// ErrEmailTaken is returned by Create when the email already exists.
var ErrEmailTaken = errors.New("email already registered")

// ErrHandleTaken is returned when the chosen handle collides with an existing user.
var ErrHandleTaken = errors.New("handle already in use")

// UserRepo provides CRUD on the users table.
type UserRepo struct {
	pg *Postgres
}

func NewUserRepo(pg *Postgres) *UserRepo {
	return &UserRepo{pg: pg}
}

// Create inserts a new user. Returns ErrEmailTaken or ErrHandleTaken on
// unique-violation. The caller is responsible for picking a unique handle —
// the auth service does this with a retry loop.
func (r *UserRepo) Create(ctx context.Context, email, passwordHash, name, handle string) (*model.User, error) {
	const q = `
		INSERT INTO users (email, password_hash, name, handle)
		VALUES ($1, $2, $3, $4)
		RETURNING id, email, handle, password_hash, name, avatar_url, role, plan,
		          email_verified_at, token_version, created_at, updated_at`

	u := &model.User{}
	err := r.pg.Pool.QueryRow(ctx, q,
		strings.ToLower(strings.TrimSpace(email)), passwordHash, name, handle,
	).Scan(&u.ID, &u.Email, &u.Handle, &u.PasswordHash, &u.Name, &u.AvatarURL, &u.Role, &u.Plan,
		&u.EmailVerifiedAt, &u.TokenVersion, &u.CreatedAt, &u.UpdatedAt)
	if err != nil {
		if isUniqueViolation(err, "users_handle_key") {
			return nil, ErrHandleTaken
		}
		if isUniqueViolation(err, "users_email_key") {
			return nil, ErrEmailTaken
		}
		return nil, fmt.Errorf("create user: %w", err)
	}
	return u, nil
}

// FindByEmail returns the user with the given email, or ErrUserNotFound.
func (r *UserRepo) FindByEmail(ctx context.Context, email string) (*model.User, error) {
	return r.findOne(ctx,
		`WHERE email = $1`, strings.ToLower(strings.TrimSpace(email)))
}

// FindByID returns the user with the given id, or ErrUserNotFound.
func (r *UserRepo) FindByID(ctx context.Context, id string) (*model.User, error) {
	return r.findOne(ctx, `WHERE id = $1`, id)
}

// FindByHandle returns the user with the given handle (case-insensitive
// thanks to the citext column), or ErrUserNotFound.
func (r *UserRepo) FindByHandle(ctx context.Context, handle string) (*model.User, error) {
	return r.findOne(ctx, `WHERE handle = $1`, strings.TrimSpace(handle))
}

func (r *UserRepo) findOne(ctx context.Context, where string, args ...any) (*model.User, error) {
	q := `
		SELECT id, email, handle, password_hash, name, avatar_url, role, plan,
		       email_verified_at, token_version, created_at, updated_at
		FROM users ` + where + ` LIMIT 1`

	u := &model.User{}
	err := r.pg.Pool.QueryRow(ctx, q, args...).
		Scan(&u.ID, &u.Email, &u.Handle, &u.PasswordHash, &u.Name, &u.AvatarURL, &u.Role, &u.Plan,
			&u.EmailVerifiedAt, &u.TokenVersion, &u.CreatedAt, &u.UpdatedAt)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrUserNotFound
		}
		return nil, fmt.Errorf("find user: %w", err)
	}
	return u, nil
}

// UpdateProfile updates the user's name, avatar, and/or handle. Pass nil to
// leave a field unchanged. Returns the updated user.
//
// `handle` collisions surface as ErrHandleTaken so the handler can render
// a useful message.
func (r *UserRepo) UpdateProfile(ctx context.Context, id string, name, avatarURL, handle *string) (*model.User, error) {
	const q = `
		UPDATE users
		   SET name       = COALESCE($2, name),
		       avatar_url = CASE WHEN $3::boolean THEN $4 ELSE avatar_url END,
		       handle     = COALESCE($5, handle),
		       updated_at = now()
		 WHERE id = $1
		RETURNING id, email, handle, password_hash, name, avatar_url, role, plan,
		          email_verified_at, token_version, created_at, updated_at`

	// $3 is a flag: "did the caller intend to set avatar_url (including to NULL)?"
	// If avatarURL is nil we leave it alone; otherwise we apply *avatarURL (which
	// may itself be the empty string — caller decides if "" should map to NULL).
	updateAvatar := avatarURL != nil
	var avatarVal *string
	if updateAvatar && *avatarURL != "" {
		avatarVal = avatarURL
	}

	u := &model.User{}
	err := r.pg.Pool.QueryRow(ctx, q, id, name, updateAvatar, avatarVal, handle).
		Scan(&u.ID, &u.Email, &u.Handle, &u.PasswordHash, &u.Name, &u.AvatarURL, &u.Role, &u.Plan,
			&u.EmailVerifiedAt, &u.TokenVersion, &u.CreatedAt, &u.UpdatedAt)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrUserNotFound
		}
		if isUniqueViolation(err, "users_handle_key") {
			return nil, ErrHandleTaken
		}
		return nil, fmt.Errorf("update profile: %w", err)
	}
	return u, nil
}

// UpdatePassword sets a new password hash and bumps token_version so any
// existing JWTs immediately become invalid.
func (r *UserRepo) UpdatePassword(ctx context.Context, id, newHash string) error {
	const q = `
		UPDATE users
		   SET password_hash = $2,
		       token_version = token_version + 1,
		       updated_at    = now()
		 WHERE id = $1`
	tag, err := r.pg.Pool.Exec(ctx, q, id, newHash)
	if err != nil {
		return fmt.Errorf("update password: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrUserNotFound
	}
	return nil
}

// MarkEmailVerified sets email_verified_at = now() if not already set.
func (r *UserRepo) MarkEmailVerified(ctx context.Context, id string) error {
	const q = `UPDATE users SET email_verified_at = now(), updated_at = now()
	           WHERE id = $1 AND email_verified_at IS NULL`
	_, err := r.pg.Pool.Exec(ctx, q, id)
	if err != nil {
		return fmt.Errorf("mark verified: %w", err)
	}
	return nil
}

// Helper for unique-violation detection. Avoids importing pgconn just for
// the SQLSTATE; we string-match on the message which contains the constraint
// name. Good enough for the one constraint we care about.
func isUniqueViolation(err error, constraint string) bool {
	if err == nil {
		return false
	}
	msg := err.Error()
	return strings.Contains(msg, "23505") || strings.Contains(msg, constraint)
}

// AuthTokenRepo handles password_reset + email_verification tokens.
type AuthTokenRepo struct {
	pg *Postgres
}

func NewAuthTokenRepo(pg *Postgres) *AuthTokenRepo {
	return &AuthTokenRepo{pg: pg}
}

// Create inserts a new token row. `tokenHash` must be the SHA-256 hex of the
// raw token; only the hash is stored, never the plaintext.
func (r *AuthTokenRepo) Create(ctx context.Context, userID, purpose, tokenHash string, ttl time.Duration) (*model.AuthToken, error) {
	const q = `
		INSERT INTO auth_tokens (user_id, purpose, token_hash, expires_at)
		VALUES ($1, $2, $3, $4)
		RETURNING id, user_id, purpose, token_hash, expires_at, used_at, created_at`

	t := &model.AuthToken{}
	err := r.pg.Pool.QueryRow(ctx, q, userID, purpose, tokenHash, time.Now().Add(ttl)).
		Scan(&t.ID, &t.UserID, &t.Purpose, &t.TokenHash, &t.ExpiresAt, &t.UsedAt, &t.CreatedAt)
	if err != nil {
		return nil, fmt.Errorf("create auth_token: %w", err)
	}
	return t, nil
}

// FindValid returns a non-used, non-expired token by hash + purpose.
func (r *AuthTokenRepo) FindValid(ctx context.Context, tokenHash, purpose string) (*model.AuthToken, error) {
	const q = `
		SELECT id, user_id, purpose, token_hash, expires_at, used_at, created_at
		FROM auth_tokens
		WHERE token_hash = $1
		  AND purpose    = $2
		  AND used_at    IS NULL
		  AND expires_at > now()
		LIMIT 1`

	t := &model.AuthToken{}
	err := r.pg.Pool.QueryRow(ctx, q, tokenHash, purpose).
		Scan(&t.ID, &t.UserID, &t.Purpose, &t.TokenHash, &t.ExpiresAt, &t.UsedAt, &t.CreatedAt)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrUserNotFound
		}
		return nil, fmt.Errorf("find token: %w", err)
	}
	return t, nil
}

// Consume marks a token as used. After this call the token can never be
// honoured again, even if it has not yet expired.
func (r *AuthTokenRepo) Consume(ctx context.Context, id string) error {
	const q = `UPDATE auth_tokens SET used_at = now() WHERE id = $1 AND used_at IS NULL`
	_, err := r.pg.Pool.Exec(ctx, q, id)
	if err != nil {
		return fmt.Errorf("consume token: %w", err)
	}
	return nil
}

// InvalidatePending marks all not-yet-used tokens for a user+purpose as used.
// Called when a fresh token is issued so old links are immediately dead.
func (r *AuthTokenRepo) InvalidatePending(ctx context.Context, userID, purpose string) error {
	const q = `UPDATE auth_tokens SET used_at = now()
	           WHERE user_id = $1 AND purpose = $2 AND used_at IS NULL`
	_, err := r.pg.Pool.Exec(ctx, q, userID, purpose)
	if err != nil {
		return fmt.Errorf("invalidate pending tokens: %w", err)
	}
	return nil
}