From 6998a0fa0a3caa1314bf4dc85cdfd02f1e1a6fce Mon Sep 17 00:00:00 2001
From: omicron <omicron.me@protonmail.com>
Date: Thu, 8 May 2025 14:18:54 +0200
Subject: [PATCH] Add basic database interaction

---
 go.mod                       |   2 +
 go.sum                       |   2 +
 internal/database/manager.go | 163 +++++++++++++++++++++++++++++++++++
 3 files changed, 167 insertions(+)
 create mode 100644 internal/database/manager.go

diff --git a/go.mod b/go.mod
index ffc716f..fa4115e 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module git.omicron.one/omicron/linkshare
 
 go 1.24
+
+require github.com/mattn/go-sqlite3 v1.14.28
diff --git a/go.sum b/go.sum
index e69de29..42e5bac 100644
--- a/go.sum
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/mattn/go-sqlite3 v1.14.28 h1:ThEiQrnbtumT+QMknw63Befp/ce/nUPgBPMlRFEum7A=
+github.com/mattn/go-sqlite3 v1.14.28/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
diff --git a/internal/database/manager.go b/internal/database/manager.go
new file mode 100644
index 0000000..cd11188
--- /dev/null
+++ b/internal/database/manager.go
@@ -0,0 +1,163 @@
+// Package database provides all database interactions for linkshare.
+// This includes functions to read and write structured link data, setting and
+// getting configurations, updating and initializing the schema and backing up
+// data
+package database
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+const expectedSchemaVersion = 1
+
+// DB represents a database connection
+type DB struct {
+	conn *sql.DB
+}
+
+var (
+	ErrDatabaseNotInitialized     = errors.New("database not initialized")
+	ErrDatabaseAlreadyInitialized = errors.New("database already initialized")
+	ErrDatabaseSchemaOutdated     = errors.New("database schema needs updating")
+	ErrDatabaseSchemaUnsupported  = errors.New("database schema is too new for the server")
+	ErrMigrationFailed            = errors.New("migration failed")
+)
+
+// Open opens a connection to the sqlite database at the given path
+func Open(dbPath string) (*DB, error) {
+	conn, err := sql.Open("sqlite3", dbPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open database: %w", err)
+	}
+
+	conn.SetMaxOpenConns(1) // SQLite only supports one writer at a time
+
+	if err := conn.Ping(); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("failed to ping database: %w", err)
+	}
+
+	_, err = conn.Exec("PRAGMA foreign_keys = ON")
+	if err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("failed to enable foreign key constraints: %w", err)
+	}
+
+	return &DB{conn: conn}, nil
+}
+
+// Close closes the database connection if it's open
+func (db *DB) Close() error {
+	if db.conn != nil {
+		return db.conn.Close()
+	}
+	return nil
+}
+
+// Initialize the database schema
+func (db *DB) Initialize(schemaPath string) error {
+	err := db.CheckInitialized()
+	if err == nil {
+		return ErrDatabaseAlreadyInitialized
+	}
+
+	currentSchema := filepath.Join(schemaPath, "current.sql")
+	schema, err := os.ReadFile(currentSchema)
+	if err != nil {
+		return fmt.Errorf("failed to read schema file: %w", err)
+	}
+
+	_, err = db.conn.Exec(string(schema))
+	if err != nil {
+		return fmt.Errorf("failed to initialize database: %w", err)
+	}
+
+	return nil
+}
+
+// CheckInitialized returns nil if the database is initialized and an error otherwise
+func (db *DB) CheckInitialized() error {
+	var count int
+	err := db.conn.QueryRow("SELECT count(*) FROM sqlite_master WHERE type='table' AND name='settings'").Scan(&count)
+	if err != nil {
+		return fmt.Errorf("failed to check if database is initialized: %w", err)
+	}
+
+	if count == 0 {
+		return ErrDatabaseNotInitialized
+	}
+	return nil
+}
+
+// GetSchemaVersion returns the schema version or an error
+func (db *DB) GetSchemaVersion() (int, error) {
+	var version string
+	err := db.conn.QueryRow("SELECT value FROM settings WHERE key='schema-version'").Scan(&version)
+	if err != nil {
+		return 0, fmt.Errorf("failed to get schema version: %w", err)
+	}
+
+	versionInt, err := strconv.Atoi(version)
+	if err != nil {
+		return 0, fmt.Errorf("invalid schema version: %w", err)
+	}
+
+	if versionInt < 1 {
+		return 0, fmt.Errorf("invalid schema version %d", versionInt)
+	}
+
+	return versionInt, nil
+}
+
+// CheckSchemaVersion verifies that the schema is initialized and has the correct version
+func (db *DB) CheckSchemaVersion() error {
+	err := db.CheckInitialized()
+	if err != nil {
+		return err
+	}
+	version, err := db.GetSchemaVersion()
+	if err != nil {
+		return err
+	}
+	if version < expectedSchemaVersion {
+		return ErrDatabaseSchemaOutdated
+	} else if version > expectedSchemaVersion {
+		return ErrDatabaseSchemaUnsupported
+	}
+	return nil
+}
+
+func (db *DB) transaction(ctx context.Context, fn func(*sql.Tx) error) error {
+	tx, err := db.conn.BeginTx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf("failed to begin transaction: %w", err)
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			tx.Rollback()
+			panic(p)
+		}
+	}()
+
+	if err := fn(tx); err != nil {
+		if rbErr := tx.Rollback(); rbErr != nil {
+			return fmt.Errorf("error rolling back transaction: %v (original error: %w)", rbErr, err)
+		}
+		return err
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("failed to commit transaction: %w", err)
+	}
+
+	return nil
+}