2 files changed, 229 insertions, 0 deletions
diff --git a/src/main/kotlin/moe/nea/ledger/database/DBSchema.kt b/src/main/kotlin/moe/nea/ledger/database/DBSchema.kt
new file mode 100644
index 0000000..49e2048
--- /dev/null
+++ b/src/main/kotlin/moe/nea/ledger/database/DBSchema.kt
@@ -0,0 +1,206 @@
+package moe.nea.ledger.database
+
+import java.sql.Connection
+import java.sql.PreparedStatement
+import java.sql.ResultSet
+import java.time.Instant
+
+interface DBSchema {
+	val tables: List<Table>
+}
+
+interface DBType<T> {
+	val dbType: String
+
+	fun get(result: ResultSet, index: Int): T
+	fun set(stmt: PreparedStatement, index: Int, value: T)
+	fun getName(): String = javaClass.simpleName
+}
+
+object DBString : DBType<String> {
+	override val dbType: String
+		get() = "TEXT"
+
+	override fun get(result: ResultSet, index: Int): String {
+		return result.getString(index)
+	}
+
+	override fun set(stmt: PreparedStatement, index: Int, value: String) {
+		stmt.setString(index, value)
+	}
+}
+
+object DBInt : DBType<Long> {
+	override val dbType: String
+		get() = "INTEGER"
+
+	override fun get(result: ResultSet, index: Int): Long {
+		return result.getLong(index)
+	}
+
+	override fun set(stmt: PreparedStatement, index: Int, value: Long) {
+		stmt.setLong(index, value)
+	}
+}
+
+object DBInstant : DBType<Instant> {
+	override val dbType: String
+		get() = "INTEGER"
+
+	override fun set(stmt: PreparedStatement, index: Int, value: Instant) {
+		stmt.setLong(index, value.toEpochMilli())
+	}
+
+	override fun get(result: ResultSet, index: Int): Instant {
+		return Instant.ofEpochMilli(result.getLong(index))
+	}
+}
+
+// TODO: add table
+class Column<T> @Deprecated("Use Table.column instead") constructor(val name: String, val type: DBType<T>) {
+	val sqlName get() = "`$name`"
+}
+
+interface Constraint {
+	fun asSQL(): String
+}
+
+class UniqueConstraint(val columns: List<Column<*>>) : Constraint {
+	init {
+		require(columns.isNotEmpty())
+	}
+
+	override fun asSQL(): String {
+		return "UNIQUE (${columns.joinToString() { it.sqlName }})"
+	}
+}
+
+abstract class Table(val name: String) {
+	val sqlName get() = "`$name`"
+	protected val _mutable_columns: MutableList<Column<*>> = mutableListOf()
+	protected val _mutable_constraints: MutableList<Constraint> = mutableListOf()
+	val columns: List<Column<*>> get() = _mutable_columns
+	val constraints get() = _mutable_constraints
+	protected fun unique(vararg columns: Column<*>) {
+		_mutable_constraints.add(UniqueConstraint(columns.toList()))
+	}
+
+	protected fun <T> column(name: String, type: DBType<T>): Column<T> {
+		@Suppress("DEPRECATION") val column = Column(name, type)
+		_mutable_columns.add(column)
+		return column
+	}
+
+	fun debugSchema() {
+		val nameWidth = columns.maxOf { it.name.length }
+		val typeWidth = columns.maxOf { it.type.getName().length }
+		val totalWidth = maxOf(2 + nameWidth + 3 + typeWidth + 2, name.length + 4)
+		val adjustedTypeWidth = totalWidth - nameWidth - 2 - 3 - 2
+
+		var string = "\n"
+		string += ("+" + "-".repeat(totalWidth - 2) + "+\n")
+		string += ("| $name${" ".repeat(totalWidth - 4 - name.length)} |\n")
+		string += ("+" + "-".repeat(totalWidth - 2) + "+\n")
+		for (column in columns) {
+			string += ("| ${column.name}${" ".repeat(nameWidth - column.name.length)} |")
+			string += (" ${column.type.getName()}" +
+					"${" ".repeat(adjustedTypeWidth - column.type.getName().length)} |\n")
+		}
+		string += ("+" + "-".repeat(totalWidth - 2) + "+")
+		println(string)
+	}
+
+	fun createIfNotExists(connection: Connection) {
+		val properties = mutableListOf<String>()
+		for (column in columns) {
+			properties.add("${column.sqlName} ${column.type.dbType}")
+		}
+		for (constraint in constraints) {
+			properties.add(constraint.asSQL())
+		}
+		connection.prepareAndLog("CREATE TABLE IF NOT EXISTS `$name` (" + properties.joinToString() + ")")
+			.execute()
+	}
+
+
+	fun selectAll(connection: Connection): Query {
+		return Query(connection, columns, this)
+	}
+}
+
+fun Connection.prepareAndLog(statement: String): PreparedStatement {
+	println("Preparing to execute $statement")
+	return prepareStatement(statement)
+}
+
+class Query(
+	val connection: Connection,
+	val selectedColumns: List<Column<*>>,
+	var table: Table,
+	var limit: UInt? = null,
+	var skip: UInt? = null,
+//	var order: OrderClause?= null,
+//	val condition: List<SqlCondition>
+) : Iterable<ResultRow> {
+	fun skip(skip: UInt): Query {
+		require(limit != null)
+		this.skip = skip
+		return this
+	}
+
+	fun limit(limit: UInt): Query {
+		this.limit = limit
+		return this
+	}
+
+	override fun iterator(): Iterator<ResultRow> {
+		val columnSelections = selectedColumns.joinToString { it.sqlName }
+		var query = "SELECT $columnSelections FROM ${table.sqlName} "
+		if (limit != null) {
+			query += "LIMIT $limit "
+			if (skip != null) {
+				query += "OFFSET $skip "
+			}
+		}
+		val prepared = connection.prepareAndLog(query)
+		val results = prepared.executeQuery()
+		return object : Iterator<ResultRow> {
+			var hasAdvanced = false
+			var hasEnded = false
+			override fun hasNext(): Boolean {
+				if (hasEnded) return false
+				if (hasAdvanced) return true
+				if (results.next()) {
+					hasAdvanced = true
+					return true
+				} else {
+					hasEnded = true
+					return false
+				}
+			}
+
+			override fun next(): ResultRow {
+				if (!hasNext()) {
+					throw NoSuchElementException()
+				}
+				hasAdvanced = false
+				return ResultRow(selectedColumns.withIndex().associate {
+					it.value to it.value.type.get(results, it.index + 1)
+				})
+			}
+
+		}
+	}
+}
+
+class ResultRow(val columnValues: Map<Column<*>, *>) {
+	operator fun <T> get(column: Column<T>): T {
+		val value = columnValues[column]
+			?: error("Invalid column ${column.name}. Only ${columnValues.keys.joinToString { it.name }} are available.")
+		return value as T
+	}
+}
+
+
+
+
diff --git a/src/main/kotlin/moe/nea/ledger/database/Database.kt b/src/main/kotlin/moe/nea/ledger/database/Database.kt
new file mode 100644
index 0000000..d14a0e2
--- /dev/null
+++ b/src/main/kotlin/moe/nea/ledger/database/Database.kt
@@ -0,0 +1,23 @@
+package moe.nea.ledger.database
+
+import java.sql.DriverManager
+
+object Database {
+	val connection = DriverManager.getConnection("jdbc:sqlite:money-ledger/database.db")
+
+	object MetaTable : Table("LedgerMeta") {
+		val key = column("key", DBString)
+		val value = column("value", DBString)
+
+		init {
+			unique(key)
+		}
+	}
+
+	fun init() {
+		MetaTable.createIfNotExists(connection)
+		val meta = MetaTable.selectAll(connection).associate { it[MetaTable.key] to it[MetaTable.value] }
+		println("Old Meta: $meta")
+	}
+
+}
+\ No newline at end of file