// Package store owns the encrypted SQLite config and read state.
package store

import (
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strconv"

	_ "modernc.org/sqlite"
)

// Store wraps the database and the field-encryption key.
type Store struct {
	db  *sql.DB
	key []byte
}

// Open opens (creating if needed) the DB at path and applies the schema.
// The store opens LOCKED: call InitKeys (first run) or Unlock before any
// secret read/write.
func Open(path string) (*Store, error) {
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		return nil, fmt.Errorf("create db dir: %w", err)
	}
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, err
	}
	// Pin pool to a single connection so PRAGMA foreign_keys = ON sticks.
	// SQLite PRAGMAs are connection-scoped; pool would otherwise create
	// new connections without the pragma set.
	db.SetMaxOpenConns(1)
	if _, err := db.Exec("PRAGMA foreign_keys = ON;"); err != nil {
		db.Close()
		return nil, err
	}
	if _, err := db.Exec(schemaSQL); err != nil {
		db.Close()
		return nil, fmt.Errorf("apply schema: %w", err)
	}
	s := &Store{db: db}
	if err := s.migrate(); err != nil {
		db.Close()
		return nil, err
	}
	return s, nil
}

// migrate brings an existing database up to the current schemaVersion. A brand-
// new database (no schema_version yet) already has every column from schemaSQL,
// so it is simply stamped at the current version. Each older version runs its
// forward step. The version gate makes every step idempotent across reopens.
func (s *Store) migrate() error {
	v, err := s.GetSetting("schema_version")
	if err != nil {
		// Fresh database: schemaSQL created all columns already.
		return s.SetSetting("schema_version", strconv.Itoa(schemaVersion))
	}
	var ver int
	ver, err = strconv.Atoi(v)
	if err != nil {
		return fmt.Errorf("invalid schema_version %q: %w", v, err)
	}
	if ver < 2 {
		if _, err := s.db.Exec(`ALTER TABLE accounts ADD COLUMN from_address TEXT`); err != nil {
			return fmt.Errorf("migrate to v2: %w", err)
		}
		if err := s.SetSetting("schema_version", "2"); err != nil {
			return err
		}
	}
	return nil
}

func (s *Store) Close() error { return s.db.Close() }

// DefaultDBPath resolves EMCLI_DB or the per-OS default location.
func DefaultDBPath() (string, error) {
	if p := os.Getenv("EMCLI_DB"); p != "" {
		return p, nil
	}
	if runtime.GOOS == "windows" {
		if dir := os.Getenv("AppData"); dir != "" {
			return filepath.Join(dir, "emcli", "emcli.db"), nil
		}
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(home, ".config", "emcli", "emcli.db"), nil
}