// Package store owns the single embedded SQLite database backing the zhanlu
// proxy: token-usage records (the requests table) and the persisted login
// credentials (the credentials table, single-tenant single row). It implements
// stats.Recorder for usage tracking and exposes Load/Save for credentials.
package store

import (
	"database/sql"
	"fmt"
	"strings"

	_ "modernc.org/sqlite"
)

// Store is the single owner of the proxy's SQLite database handle.
type Store struct {
	db *sql.DB
}

// Open opens (or creates) the database at path and ensures both tables exist.
// SQLite is opened with WAL journaling and a busy timeout so concurrent reads
// (stats queries) and writes (request records, credential saves) do not
// collide.
func Open(path string) (*Store, error) {
	db, err := sql.Open("sqlite", path+"?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)&_pragma=synchronous(NORMAL)&_pragma=foreign_keys(ON)")
	if err != nil {
		return nil, fmt.Errorf("open db %q: %w", path, err)
	}
	if err := ensureSchema(db); err != nil {
		db.Close()
		return nil, err
	}
	return &Store{db: db}, nil
}

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

func ensureSchema(db *sql.DB) error {
	stmts := []string{
		`CREATE TABLE IF NOT EXISTS requests (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  ts INTEGER NOT NULL,
  model TEXT NOT NULL,
  stream INTEGER NOT NULL DEFAULT 0,
  prompt_tokens INTEGER NOT NULL DEFAULT 0,
  completion_tokens INTEGER NOT NULL DEFAULT 0,
  total_tokens INTEGER NOT NULL DEFAULT 0,
  reasoning_tokens INTEGER NOT NULL DEFAULT 0,
  cached_tokens INTEGER NOT NULL DEFAULT 0,
  status TEXT NOT NULL DEFAULT 'success',
  latency_ms INTEGER NOT NULL DEFAULT 0
)`,
		`CREATE TABLE IF NOT EXISTS credentials (
  id INTEGER PRIMARY KEY CHECK (id = 1),
  access_key TEXT NOT NULL DEFAULT '',
  secret_key TEXT NOT NULL DEFAULT '',
  token TEXT NOT NULL DEFAULT '',
  api_key TEXT NOT NULL DEFAULT '',
  model_base_url TEXT NOT NULL DEFAULT '',
  email TEXT NOT NULL DEFAULT '',
  organization TEXT NOT NULL DEFAULT '',
  team TEXT NOT NULL DEFAULT '',
  base_url TEXT NOT NULL DEFAULT '',
  saved_at INTEGER NOT NULL DEFAULT 0
)`,
		`CREATE INDEX IF NOT EXISTS idx_requests_ts ON requests(ts)`,
		`CREATE INDEX IF NOT EXISTS idx_requests_model ON requests(model)`,
		// Ensure the single credentials row exists so UPSERTs and SELECTs always
		// have a target.
		`INSERT INTO credentials (id) VALUES (1) ON CONFLICT(id) DO NOTHING`,
	}
	for _, q := range stmts {
		if _, err := db.Exec(q); err != nil {
			return fmt.Errorf("schema: %w", err)
		}
	}
	// Add cached_tokens to databases created before this column existed. SQLite
	// returns "duplicate column name" when it already exists; that is expected
	// and ignored.
	if _, err := db.Exec(`ALTER TABLE requests ADD COLUMN cached_tokens INTEGER NOT NULL DEFAULT 0`); err != nil {
		if !strings.Contains(err.Error(), "duplicate column") {
			return fmt.Errorf("migrate cached_tokens: %w", err)
		}
	}
	return nil
}