// Package adminbootstrap safely initializes the first Chorus administrator.
package adminbootstrap

import (
	"context"
	"database/sql"
	"errors"
	"strings"

	"golang.org/x/crypto/bcrypt"
)

const chorusOperatorRoleKey = "chorus_operator"

var (
	ErrMigrationPrecondition = errors.New("administrator bootstrap prerequisites are unavailable")
	ErrAccountState          = errors.New("administrator account is not eligible for bootstrap")
	ErrDatabaseUnavailable   = errors.New("cannot connect to administrator database")
)

// Config contains the external inputs accepted by the bootstrap command.
// Password is intentionally held only in memory and is never included in errors.
type Config struct {
	DSN           string
	Username      string
	Password      string
	ResetPassword bool
}

// Result describes the non-sensitive effect of one bootstrap run.
type Result int

const (
	Created Result = iota + 1
	Unchanged
	PasswordReset
)

// LoadConfig reads the command's dedicated environment variables. It does not
// accept defaults so an operator must make every bootstrap action explicit.
func LoadConfig(lookup func(string) (string, bool)) (Config, error) {
	read := func(name string) string {
		value, _ := lookup(name)
		return value
	}

	cfg := Config{
		DSN:      strings.TrimSpace(read("CHORUS_DSN")),
		Username: strings.TrimSpace(read("CHORUS_ADMIN_USERNAME")),
		Password: read("CHORUS_ADMIN_PASSWORD"),
	}
	if value, ok := lookup("CHORUS_ADMIN_RESET_PASSWORD"); ok && value != "" {
		if value != "1" {
			return Config{}, errors.New("CHORUS_ADMIN_RESET_PASSWORD must be 1 when set")
		}
		cfg.ResetPassword = true
	}
	return cfg, cfg.Validate()
}

// Validate rejects inputs that cannot be represented safely in the audited
// schema or processed by bcrypt. It never includes values in returned errors.
func (c Config) Validate() error {
	if strings.TrimSpace(c.DSN) == "" {
		return errors.New("CHORUS_DSN is required")
	}
	if c.Username == "" {
		return errors.New("CHORUS_ADMIN_USERNAME is required")
	}
	if len([]byte(c.Username)) > 64 {
		return errors.New("CHORUS_ADMIN_USERNAME exceeds 64 bytes")
	}
	if c.Password == "" {
		return errors.New("CHORUS_ADMIN_PASSWORD is required")
	}
	if len([]byte(c.Password)) > 72 {
		return errors.New("CHORUS_ADMIN_PASSWORD exceeds 72 bytes")
	}
	return nil
}

// Bootstrap creates an enabled administrator or explicitly resets its password.
// Existing records are never repaired implicitly: a disabled, deleted, empty-
// password, or role-mismatched account is treated as an operator intervention.
func Bootstrap(ctx context.Context, db *sql.DB, cfg Config) (Result, error) {
	return bootstrap(ctx, db, cfg, chorusOperatorRoleKey)
}

func bootstrap(ctx context.Context, db *sql.DB, cfg Config, roleKey string) (Result, error) {
	if err := cfg.Validate(); err != nil {
		return 0, err
	}
	if db == nil {
		return 0, ErrDatabaseUnavailable
	}
	if err := db.PingContext(ctx); err != nil {
		return 0, ErrDatabaseUnavailable
	}

	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return 0, ErrDatabaseUnavailable
	}
	defer tx.Rollback()

	roleID, err := activeChorusOperatorRole(ctx, tx, roleKey)
	if err != nil {
		return 0, err
	}

	var (
		userID       int64
		storedHash   string
		status       string
		storedRoleID int64
		active       bool
	)
	err = tx.QueryRowContext(ctx, `
SELECT user_id, password, status, role_id, deleted_at IS NULL
FROM sys_user
WHERE username = ?
FOR UPDATE`, cfg.Username).Scan(&userID, &storedHash, &status, &storedRoleID, &active)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		hash, hashErr := bcryptHash(cfg.Password)
		if hashErr != nil {
			return 0, hashErr
		}
		if _, err := tx.ExecContext(ctx, `
INSERT INTO sys_user (username, password, role_id, status)
VALUES (?, ?, ?, '2')`, cfg.Username, hash, roleID); err != nil {
			return 0, ErrDatabaseUnavailable
		}
		if err := tx.Commit(); err != nil {
			return 0, ErrDatabaseUnavailable
		}
		return Created, nil
	case err != nil:
		return 0, ErrDatabaseUnavailable
	}

	if !active || status != "2" || storedRoleID != roleID || storedHash == "" {
		return 0, ErrAccountState
	}
	if !cfg.ResetPassword {
		if err := tx.Commit(); err != nil {
			return 0, ErrDatabaseUnavailable
		}
		return Unchanged, nil
	}

	hash, err := bcryptHash(cfg.Password)
	if err != nil {
		return 0, err
	}
	result, err := tx.ExecContext(ctx, `
UPDATE sys_user
SET password = ?, salt = '', update_by = 0
WHERE user_id = ? AND role_id = ? AND status = '2' AND deleted_at IS NULL`, hash, userID, roleID)
	if err != nil {
		return 0, ErrDatabaseUnavailable
	}
	rowsAffected, err := result.RowsAffected()
	if err != nil || rowsAffected != 1 {
		return 0, ErrAccountState
	}
	if err := tx.Commit(); err != nil {
		return 0, ErrDatabaseUnavailable
	}
	return PasswordReset, nil
}

func activeChorusOperatorRole(ctx context.Context, tx *sql.Tx, roleKey string) (int64, error) {
	var roleID int64
	err := tx.QueryRowContext(ctx, `
SELECT role_id
FROM sys_role
WHERE role_key = ? AND status = '2' AND deleted_at IS NULL
FOR UPDATE`, roleKey).Scan(&roleID)
	if errors.Is(err, sql.ErrNoRows) {
		return 0, ErrMigrationPrecondition
	}
	if err != nil {
		return 0, ErrDatabaseUnavailable
	}
	return roleID, nil
}

func bcryptHash(password string) (string, error) {
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", errors.New("cannot generate administrator password hash")
	}
	return string(hash), nil
}