// Package store keeps Housecarl's data in SQLite: the configuration, the
// history of changes, users, tokens, sessions and the audit log.
//
// The configuration is loaded into a model.State as a whole and saved as
// changes (model.Change), one JSON row per object.
package store

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	_ "modernc.org/sqlite"
)

// ErrNotFound is returned when a row does not exist.
var ErrNotFound = errors.New("not found")

// ErrConflict is returned for unique constraint violations.
var ErrConflict = errors.New("already exists")

// Store is a Housecarl database.
type Store struct {
	db *sql.DB
}

// DB exposes the database (backups, tests).
func (s *Store) DB() *sql.DB { return s.db }

// Path is the database file ("" in memory).
func (s *Store) Path() string {
	var file string
	if err := s.db.QueryRow(`SELECT file FROM pragma_database_list WHERE name = 'main'`).Scan(&file); err != nil {
		return ""
	}
	return file
}

// Open opens (creating if needed) the database at path and applies
// migrations. ":memory:" makes a throwaway database.
func Open(path string) (*Store, error) {
	dsn := "file:" + path + "?_pragma=busy_timeout(10000)&_pragma=foreign_keys(1)&_pragma=synchronous(NORMAL)&_txlock=immediate&_pragma=journal_mode(WAL)"
	if path == ":memory:" {
		dsn = "file::memory:?_pragma=foreign_keys(1)&_txlock=immediate"
	}
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, err
	}
	if path == ":memory:" {
		db.SetMaxOpenConns(1)
	}
	s := &Store{db: db}
	if err := s.migrate(context.Background()); err != nil {
		db.Close()
		return nil, fmt.Errorf("migrating database: %w", err)
	}
	return s, nil
}

// OpenExisting opens a database without creating or migrating it, for
// commands that run next to a running housecarld ('housecarld backup').
func OpenExisting(path string) (*Store, error) {
	db, err := sql.Open("sqlite", "file:"+path+"?mode=rw&_pragma=busy_timeout(10000)&_pragma=foreign_keys(1)&_txlock=immediate")
	if err != nil {
		return nil, err
	}
	if err := db.Ping(); err != nil {
		db.Close()
		return nil, err
	}
	return &Store{db: db}, nil
}

// Close closes the database.
func (s *Store) Close() error { return s.db.Close() }

// SchemaVersion is the schema version this Housecarl uses.
func SchemaVersion() int { return len(migrations) }

// Append new migrations; never edit one that has shipped.
var migrations = []string{
	// 1: initial schema
	`
CREATE TABLE meta (key TEXT PRIMARY KEY, value TEXT NOT NULL);
CREATE TABLE seq (name TEXT PRIMARY KEY, value INTEGER NOT NULL);
INSERT INTO seq (name, value) VALUES ('object', 0);

-- The configuration: one row per object (zone, set, service, rule,
-- forward, snat, redirect), as JSON. The settings are in meta.
CREATE TABLE objects (
	kind TEXT NOT NULL,
	id INTEGER NOT NULL,
	data TEXT NOT NULL,
	PRIMARY KEY (kind, id)
);

CREATE TABLE history (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	time TEXT NOT NULL,
	user_id INTEGER,
	username TEXT NOT NULL,
	via TEXT NOT NULL,
	description TEXT NOT NULL,
	changes TEXT NOT NULL,
	revert_of INTEGER,
	reverted_by INTEGER
);

CREATE TABLE users (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	username TEXT NOT NULL UNIQUE COLLATE NOCASE,
	password_hash TEXT NOT NULL DEFAULT '',
	admin INTEGER NOT NULL DEFAULT 0,
	grants TEXT NOT NULL DEFAULT '[]',
	disabled INTEGER NOT NULL DEFAULT 0,
	comment TEXT NOT NULL DEFAULT '',
	created_at TEXT NOT NULL,
	updated_at TEXT NOT NULL,
	last_login_at TEXT
);
CREATE TABLE tokens (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
	name TEXT NOT NULL,
	public_id TEXT NOT NULL UNIQUE,
	secret_hash TEXT NOT NULL,
	grants TEXT,
	expires_at TEXT,
	created_at TEXT NOT NULL,
	last_used_at TEXT,
	last_used_ip TEXT NOT NULL DEFAULT '',
	revoked_at TEXT,
	rotated_at TEXT,
	prev_secret_hash TEXT NOT NULL DEFAULT '',
	prev_expires_at TEXT
);
CREATE TABLE sessions (
	id_hash TEXT PRIMARY KEY,
	user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
	csrf_token TEXT NOT NULL,
	created_at TEXT NOT NULL,
	expires_at TEXT NOT NULL,
	last_seen_at TEXT NOT NULL,
	ip TEXT NOT NULL DEFAULT '',
	user_agent TEXT NOT NULL DEFAULT ''
);
CREATE TABLE audit (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	time TEXT NOT NULL,
	user_id INTEGER,
	username TEXT NOT NULL DEFAULT '',
	auth TEXT NOT NULL DEFAULT '',
	token_id INTEGER,
	ip TEXT NOT NULL DEFAULT '',
	action TEXT NOT NULL,
	object TEXT NOT NULL DEFAULT '',
	result TEXT NOT NULL,
	detail TEXT NOT NULL DEFAULT ''
);
CREATE INDEX audit_time ON audit (time);
`,
	// 2: changesets, staged changes to review and apply together
	`
CREATE TABLE changesets (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	user_id INTEGER,
	username TEXT NOT NULL,
	via TEXT NOT NULL,
	description TEXT NOT NULL DEFAULT '',
	status TEXT NOT NULL,
	ops TEXT NOT NULL,
	created_at TEXT NOT NULL,
	updated_at TEXT NOT NULL,
	history_id INTEGER
);
CREATE INDEX changesets_status ON changesets (status);
`,
	// 3: ban lists' bans (the lists are objects)
	`
CREATE TABLE bans (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	list_id INTEGER NOT NULL,
	address TEXT NOT NULL,
	protocol TEXT NOT NULL DEFAULT '',
	port INTEGER NOT NULL DEFAULT 0,
	expires_at TEXT,
	created_at TEXT NOT NULL,
	who TEXT NOT NULL DEFAULT '',
	source TEXT NOT NULL DEFAULT '',
	reason TEXT NOT NULL DEFAULT '',
	UNIQUE (list_id, address, protocol, port)
);
CREATE INDEX bans_expires ON bans (expires_at);
`,
}

func (s *Store) migrate(ctx context.Context) error {
	if _, err := s.db.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS schema_version (version INTEGER NOT NULL)`); err != nil {
		return err
	}
	var v int
	err := s.db.QueryRowContext(ctx, `SELECT version FROM schema_version`).Scan(&v)
	if errors.Is(err, sql.ErrNoRows) {
		if _, err := s.db.ExecContext(ctx, `INSERT INTO schema_version (version) VALUES (0)`); err != nil {
			return err
		}
	} else if err != nil {
		return err
	}
	if v > len(migrations) {
		return fmt.Errorf("database schema version %d is newer than this Housecarl (%d); upgrade Housecarl", v, len(migrations))
	}
	for i := v; i < len(migrations); i++ {
		tx, err := s.db.BeginTx(ctx, nil)
		if err != nil {
			return err
		}
		if _, err := tx.ExecContext(ctx, migrations[i]); err != nil {
			tx.Rollback()
			return fmt.Errorf("migration %d: %w", i+1, err)
		}
		if _, err := tx.ExecContext(ctx, `UPDATE schema_version SET version = ?`, i+1); err != nil {
			tx.Rollback()
			return err
		}
		if err := tx.Commit(); err != nil {
			return err
		}
	}
	return nil
}

// Version returns the database's schema version.
func (s *Store) Version(ctx context.Context) (int, error) {
	var v int
	err := s.db.QueryRowContext(ctx, `SELECT version FROM schema_version`).Scan(&v)
	return v, err
}

// AllocateIDs reserves n object IDs (all kinds share one sequence, so an
// ID names one object).
func (s *Store) AllocateIDs(ctx context.Context, n int) ([]int64, error) {
	if n <= 0 {
		return nil, nil
	}
	var last int64
	if err := s.db.QueryRowContext(ctx, `UPDATE seq SET value = value + ? WHERE name = 'object' RETURNING value`, n).Scan(&last); err != nil {
		return nil, err
	}
	ids := make([]int64, n)
	for i := range ids {
		ids[i] = last - int64(n) + 1 + int64(i)
	}
	return ids, nil
}

// GetMeta reads a meta value ("" when unset).
func (s *Store) GetMeta(ctx context.Context, key string) (string, error) {
	var v string
	err := s.db.QueryRowContext(ctx, `SELECT value FROM meta WHERE key = ?`, key).Scan(&v)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	return v, err
}

// SetMeta writes a meta value.
func (s *Store) SetMeta(ctx context.Context, key, value string) error {
	_, err := s.db.ExecContext(ctx, `INSERT INTO meta (key, value) VALUES (?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value`, key, value)
	return err
}

// Backup writes a consistent copy of the database to path.
func (s *Store) Backup(ctx context.Context, path string) error {
	_, err := s.db.ExecContext(ctx, `VACUUM INTO ?`, path)
	return err
}

// ---- helpers

const tsLayout = "2006-01-02T15:04:05.000000000Z07:00"

func ts(t time.Time) string { return t.UTC().Format(tsLayout) }

func tsPtr(t *time.Time) any {
	if t == nil {
		return nil
	}
	return ts(*t)
}

func parseTS(s string) time.Time {
	t, err := time.Parse(time.RFC3339Nano, s)
	if err != nil {
		return time.Time{}
	}
	return t
}

func parseTSPtr(s sql.NullString) *time.Time {
	if !s.Valid || s.String == "" {
		return nil
	}
	t := parseTS(s.String)
	return &t
}

func boolInt(b bool) int {
	if b {
		return 1
	}
	return 0
}

func jsonText(v any) string {
	b, err := json.Marshal(v)
	if err != nil {
		panic(err)
	}
	return string(b)
}

func isUnique(err error) bool {
	return err != nil && strings.Contains(err.Error(), "UNIQUE constraint failed")
}