using System;
using System.Collections.Generic;
using System.Data;
using System.Text;

namespace DbTools {
    public class SqlBuilder {

        public string[] GetTableNames(IDbConnection cn) {
            if (cn == null) {
                throw new ArgumentNullException("cn");
            }
            List<string> tables = new List<string>();
            if (cn.State != ConnectionState.Open) {
                cn.Open();
            }
            using (IDbCommand cmd = cn.CreateCommand()) {
                cmd.CommandText = "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' ORDER BY name;";
                using (IDataReader reader = cmd.ExecuteReader()) {
                    while (reader.Read()) {
                        tables.Add(reader.GetString(0));
                    }
                }
            }
            return tables.ToArray();
        }

        public string GetTableCreateSql(IDbConnection cn, string tableName, string selectStatement = "select * from $table") {
            if (cn == null) {
                throw new ArgumentNullException("cn");
            }
            if (string.IsNullOrEmpty(tableName)) {
                throw new ArgumentNullException("tableName");
            }

            if (cn.State != ConnectionState.Open) {
                cn.Open();
            }
            selectStatement = selectStatement.Replace("$table", tableName);
            using (IDbCommand cmd = cn.CreateCommand()) {
                cmd.CommandText = selectStatement;
                using (IDataReader reader = cmd.ExecuteReader(CommandBehavior.SchemaOnly | CommandBehavior.KeyInfo)) {
                    DataTable schemaTable = reader.GetSchemaTable();
                    if (schemaTable == null) {
                        throw new Exception("Could not get schema for table " + tableName);
                    }
                    StringBuilder sb = new StringBuilder();
                    sb.AppendLine("CREATE TABLE " + tableName + " (");
                    List<string> pkColumns = new List<string>();
                    foreach (DataRow row in schemaTable.Rows) {
                        string columnName = row["ColumnName"].ToString();
                        string dataType = row["DataTypeName"].ToString();
                        int columnSize = Convert.ToInt32(row["ColumnSize"]);
                        bool allowDBNull = Convert.ToBoolean(row["AllowDBNull"]);
                        bool isKey = Convert.ToBoolean(row["IsKey"]);
                        if (isKey) {
                            pkColumns.Add(columnName);
                        }
                        sb.Append("    " + columnName + " " + dataType);
                        if (dataType.Equals("VARCHAR", StringComparison.OrdinalIgnoreCase) ||
                            dataType.Equals("CHAR", StringComparison.OrdinalIgnoreCase) ||
                            dataType.Equals("NVARCHAR", StringComparison.OrdinalIgnoreCase) ||
                            dataType.Equals("NCHAR", StringComparison.OrdinalIgnoreCase)) {
                            sb.Append("(" + columnSize + ")");
                        }
                        if (!allowDBNull) {
                            sb.Append(" NOT NULL");
                        }
                        sb.AppendLine(",");
                    }
                    if (pkColumns.Count > 0) {
                        sb.AppendLine("    PRIMARY KEY (" + string.Join(", ", pkColumns) + ")");
                    } else {
                        // Remove the last comma
                        sb.Length -= 3;
                        sb.AppendLine();
                    }
                    sb.AppendLine(");");
                    return sb.ToString();
                }
            }
        }
    }
}