module mssql

@[params]
pub struct Config {
pub:
    conn_str string
    dsn      string
    driver   string
    server   string
    port     int
    uid      string
    user     string
    pwd      string
    password string
    // if dbname empty, conn str will not contain Database info,
    // and it is up to the server to choose which db to connect to.
    dbname  string
    options map[string]string
}

// connect creates a new connection using the provided configuration.
pub fn connect(config Config) !Connection {
    return open(config.get_conn_str())
}

// open creates a new connection using a raw ODBC connection string.
pub fn open(conn_str string) !Connection {
    mut conn := Connection{}
    conn.connect(conn_str)!
    return conn
}

fn preferred_value(primary string, fallback string) string {
    if primary != '' {
        return primary
    }
    return fallback
}

fn needs_odbc_braces(value string) bool {
    return value.contains_any(' \t\r\n;{}')
}

fn format_odbc_value(value string) string {
    if value == '' {
        return ''
    }
    if needs_odbc_braces(value) {
        return '{' + value.replace('}', '}}') + '}'
    }
    return value
}

fn append_conn_part(mut parts []string, key string, value string) {
    if value == '' {
        return
    }
    parts << '${key}=${format_odbc_value(value)}'
}

// get_conn_str builds an ODBC connection string from the configured fields.
pub fn (cfg Config) get_conn_str() string {
    if cfg.conn_str != '' {
        return cfg.conn_str
    }
    mut parts := []string{}
    append_conn_part(mut parts, 'DSN', cfg.dsn)
    append_conn_part(mut parts, 'Driver', cfg.driver)
    append_conn_part(mut parts, 'Server', cfg.server)
    if cfg.port > 0 {
        parts << 'Port=${cfg.port}'
    }
    append_conn_part(mut parts, 'UID', preferred_value(cfg.uid, cfg.user))
    append_conn_part(mut parts, 'PWD', preferred_value(cfg.pwd, cfg.password))
    if cfg.dbname != '' {
        append_conn_part(mut parts, 'Database', cfg.dbname)
    }
    if cfg.options.len > 0 {
        mut option_keys := cfg.options.keys()
        // Manual insertion sort avoids relying on the generic .sort() helper,
        // which has tripped bounds-check builds in CI.
        for i in 1 .. option_keys.len {
            key := option_keys[i]
            mut j := i
            for j > 0 && option_keys[j - 1] > key {
                option_keys[j] = option_keys[j - 1]
                j--
            }
            option_keys[j] = key
        }
        for key in option_keys {
            append_conn_part(mut parts, key, cfg.options[key])
        }
    }
    return parts.join(';')
}