// Package store 提供后端持久化：默认档为嵌入式 SQLite（单文件，零外部服务）。
// 存储档接口按设计 4.1/D16 预留 PostgreSQL 档；业务层只依赖本包公开方法。
package store

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"time"

	_ "modernc.org/sqlite"
)

// Store 持有数据库连接与对象目录。所有方法并发安全（SQLite 单写者，靠 busy 重试）。
type Store struct {
	db   *sql.DB
	dataDir string // 对象目录：data/artifacts/<id>
}

// Open 打开（必要时创建）SQLite 存储并执行迁移。
func Open(path string) (*Store, error) {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return nil, err
	}
	dsn := fmt.Sprintf("file:%s?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)&_pragma=foreign_keys(1)", path)
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, err
	}
	// SQLite 单写者：串行化写连接，避免 database is locked。
	db.SetMaxOpenConns(1)
	s := &Store{db: db, dataDir: filepath.Join(filepath.Dir(path), "artifacts")}
	if err := s.migrate(); err != nil {
		db.Close()
		return nil, err
	}
	if err := os.MkdirAll(s.dataDir, 0o755); err != nil {
		db.Close()
		return nil, err
	}
	return s, nil
}

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

func (s *Store) migrate() error {
	stmts := []string{
		`CREATE TABLE IF NOT EXISTS projects (
			id TEXT PRIMARY KEY, name TEXT NOT NULL,
			settings TEXT NOT NULL DEFAULT '{}',
			created_at TEXT NOT NULL, updated_at TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS conversations (
			id TEXT PRIMARY KEY, project_id TEXT NOT NULL,
			title TEXT NOT NULL DEFAULT '新会话', profile_id TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL, updated_at TEXT NOT NULL,
			FOREIGN KEY(project_id) REFERENCES projects(id) ON DELETE CASCADE)`,
		`CREATE TABLE IF NOT EXISTS messages (
			id TEXT PRIMARY KEY, conversation_id TEXT NOT NULL,
			run_id TEXT NOT NULL DEFAULT '', role TEXT NOT NULL,
			parts TEXT NOT NULL, seq INTEGER NOT NULL,
			created_at TEXT NOT NULL,
			FOREIGN KEY(conversation_id) REFERENCES conversations(id) ON DELETE CASCADE)`,
		`CREATE INDEX IF NOT EXISTS idx_messages_conv ON messages(conversation_id, seq)`,
		`CREATE TABLE IF NOT EXISTS runs (
			id TEXT PRIMARY KEY, parent_run_id TEXT NOT NULL DEFAULT '',
			conversation_id TEXT NOT NULL, project_id TEXT NOT NULL,
			kind TEXT NOT NULL, profile_id TEXT NOT NULL DEFAULT '',
			status TEXT NOT NULL, phase TEXT NOT NULL DEFAULT '',
			agent_name TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL, ended_at TEXT,
			usage TEXT, error TEXT)`,
		`CREATE INDEX IF NOT EXISTS idx_runs_conv ON runs(conversation_id)`,
		`CREATE INDEX IF NOT EXISTS idx_runs_parent ON runs(parent_run_id)`,
		`CREATE TABLE IF NOT EXISTS events (
			seq INTEGER PRIMARY KEY AUTOINCREMENT,
			conversation_id TEXT NOT NULL, run_id TEXT NOT NULL DEFAULT '',
			ts TEXT NOT NULL, v INTEGER NOT NULL, type TEXT NOT NULL,
			payload TEXT)`,
		`CREATE INDEX IF NOT EXISTS idx_events_conv ON events(conversation_id, seq)`,
		`CREATE TABLE IF NOT EXISTS artifacts (
			id TEXT PRIMARY KEY, project_id TEXT NOT NULL,
			name TEXT NOT NULL, kind TEXT NOT NULL, mime TEXT NOT NULL DEFAULT '',
			size INTEGER NOT NULL DEFAULT 0, source_run TEXT NOT NULL DEFAULT '',
			content_path TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL, updated_at TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS hitl_cards (
			id TEXT PRIMARY KEY, run_id TEXT NOT NULL, conversation_id TEXT NOT NULL,
			payload TEXT NOT NULL, created_at TEXT NOT NULL,
			resolved INTEGER NOT NULL DEFAULT 0, resolution TEXT)`,
		`CREATE TABLE IF NOT EXISTS profiles (
			id TEXT PRIMARY KEY, builtin INTEGER NOT NULL DEFAULT 0, payload TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS settings (
			scope TEXT PRIMARY KEY, "values" TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS plugins (
			id TEXT PRIMARY KEY, dir TEXT NOT NULL, manifest TEXT NOT NULL,
			enabled INTEGER NOT NULL DEFAULT 1, loaded_at TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS plans (
			conversation_id TEXT PRIMARY KEY, payload TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS todos (
			conversation_id TEXT PRIMARY KEY, payload TEXT NOT NULL)`,
		`CREATE TABLE IF NOT EXISTS knowledge (
			id TEXT PRIMARY KEY, project_id TEXT NOT NULL DEFAULT '',
			source TEXT NOT NULL, title TEXT NOT NULL, ref TEXT NOT NULL DEFAULT '',
			chunk TEXT NOT NULL, created_at TEXT NOT NULL)`,
		`CREATE VIRTUAL TABLE IF NOT EXISTS knowledge_fts USING fts5(title, chunk, content='knowledge', content_rowid='rowid')`,
		`CREATE TRIGGER IF NOT EXISTS knowledge_ai AFTER INSERT ON knowledge BEGIN
			INSERT INTO knowledge_fts(rowid, title, chunk) VALUES (new.rowid, new.title, new.chunk); END`,
		`CREATE TRIGGER IF NOT EXISTS knowledge_ad AFTER DELETE ON knowledge BEGIN
			INSERT INTO knowledge_fts(knowledge_fts, rowid, title, chunk) VALUES('delete', old.rowid, old.title, old.chunk); END`,
	}
	for _, q := range stmts {
		if _, err := s.db.Exec(q); err != nil {
			return fmt.Errorf("migrate: %w", err)
		}
	}
	return nil
}

// ---- 通用 ----

func nowISO() string { return time.Now().UTC().Format(time.RFC3339Nano) }

func marshalJSON(v any) string {
	b, _ := json.Marshal(v)
	return string(b)
}

func unmarshalJSON[T any](raw string) (T, error) {
	var out T
	err := json.Unmarshal([]byte(raw), &out)
	return out, err
}

var _ = unmarshalJSON[map[string]any]