const std = @import("std");
const zqlite = @import("zqlite");

pub fn init(allocator: std.mem.Allocator, path: [*:0]const u8) !zqlite.Conn {
    const flags = zqlite.OpenFlags.Create | zqlite.OpenFlags.EXResCode;
    const conn = try zqlite.open(path, flags);
    try conn.execNoArgs("PRAGMA foreign_keys = ON");
    try conn.execNoArgs("PRAGMA journal_mode = WAL");
    try migrate(allocator, conn, .{@embedFile("migrations/01.sql")});
    return conn;
}

fn migrate(allocator: std.mem.Allocator, conn: zqlite.Conn, migrations: [1][]const u8) !void {
    var version: i64 = 0;
    if (try conn.row("PRAGMA user_version", .{})) |row| {
        defer row.deinit();
        version = row.int(0);
    }

    // Start transaction
    try conn.transaction();
    errdefer conn.rollback();

    for (migrations, 1..) |migration, i| {
        const v: i64 = @intCast(i);
        if (version < v) {
            std.debug.print("Applying migration: {d}\n", .{i});

            var it = std.mem.splitScalar(u8, migration, ';');
            while (it.next()) |statement| {
                if (!is_statement_empty(statement)) {
                    try conn.exec(statement, .{});
                }
            }

            try set_version(allocator, conn, @intCast(i));
        }
    }

    // Commit transaction
    try conn.commit();
}

fn is_statement_empty(str: []const u8) bool {
    for (str) |c| {
        if (c == ' ') continue;
        if (c == '\n') continue;
        if (c == '\t') continue;
        return false;
    }
    return true;
}

fn set_version(allocator: std.mem.Allocator, conn: zqlite.Conn, version: i64) !void {
    const string = try std.fmt.allocPrint(
        allocator,
        "PRAGMA user_version = {d}",
        .{version},
    );
    defer allocator.free(string);
    try conn.exec(string, .{});
}