using System.Collections.Generic;
using System.Data.OleDb;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace DbMigrate {
    public class SqlDatabase {
        public string ConnectionString { get; set; }
        public string SqlScript { get; set; }
        public List<SqlTable> Tables { get; set; } = new List<SqlTable>();


        public SqlDatabase() {

        }

        public void Connect(string connectionString) {
            ConnectionString = connectionString;

        }

        public void LoadSql(string sql) {
            SqlScript = sql;
            Tables = ParseTablesFromSql(sql).ToList();
        }

        public void LoadSqlFromFile(string fileName) {
            if (!File.Exists(fileName)) {
                throw new FileNotFoundException("SQL file '" + fileName + "' was not found and could not be loaded.");
            }

            string sql = File.ReadAllText(fileName);
            LoadSql(sql);
        }

        public IEnumerable<SqlTable> ParseTablesFromSql(string sql) {
            SqlTable table = null;
            StringBuilder sb = new StringBuilder();

            foreach (string line in Regex.Split(sql, "\\r\\n")) {
                if (string.IsNullOrEmpty(line) || line.StartsWith("--")) {
                    continue;
                }

                if (line.ToUpper().StartsWith("CREATE TABLE ")) {
                    if (table != null) {
                        table.ParseSql(sb.ToString());
                        yield return table;
                    }

                    // Start a new table
                    table = new SqlTable();
                    sb = new StringBuilder();
                    sb.AppendLine(line);
                    continue;
                }
                sb.AppendLine(line);
            }

            table.ParseSql(sb.ToString());
            yield return table;
        }

        public async Task<string> BuildSql(string dbConnectionString, bool includeIfNotExist = false) {
            using (OleDbConnection cn = new OleDbConnection(dbConnectionString)) {
                string sql = "";

                //List<string> TableSql = new List<string>();
                IEnumerable<SqliteTableDefinition> TableDefs = await cn.QueryAsync<SqliteTableDefinition>("select * from sqlite_master");

                foreach (SqliteTableDefinition table in TableDefs.Where(f => f.type == "table").OrderBy(f => f.tbl_name)) {
                    if (table.tbl_name == "sqlite_sequence") { continue; }
                    Match m = Regex.Match(table.sql, "CREATE TABLE \\S+ \\((.*)\\)", RegexOptions.Singleline);
                    if (!m.Success) {
                        Trace.TraceWarning("Unable to match regex on table " + table.name);
                        continue;
                    }

                    int startIndex = m.Groups[1].Index;
                    int length = m.Groups[1].Length;
                    string columns = Regex.Replace(m.Groups[1].Value, "\\s{2,}", " ");
                    columns = Regex.Replace(columns.Replace(", ", ",").Replace(",\n", ","), ",(?!\\d+\\))", ",\r\n\t");

                    sql += "-- BEGIN TABLE " + table.tbl_name + " --\r\n";
                    sql += table.sql.Substring(0, startIndex) + "\r\n\t" +
                        columns.Trim() + "\r\n" +
                        table.sql.Substring(startIndex + length) + ";\r\n";


                    List<SqliteTableDefinition> indexes = TableDefs.Where(f => f.type == "index" && f.tbl_name == table.tbl_name && !string.IsNullOrEmpty(f.sql)).ToList();
                    if (indexes.Count > 0) {
                        sql += "\r\n-- INDEXES --\r\n";
                        foreach (var index in indexes) {
                            if (string.IsNullOrEmpty(index.sql)) { continue; }
                            sql += index.sql + ";\r\n";
                        }
                    }

                    List<SqliteTableDefinition> triggers = TableDefs.Where(f => f.type == "trigger" && f.tbl_name == table.tbl_name && !string.IsNullOrEmpty(f.sql)).ToList();
                    if (triggers.Count > 0) {
                        sql += "\r\n-- TRIGGERS --\r\n";
                        foreach (var trigger in triggers) {
                            if (string.IsNullOrEmpty(trigger.sql)) { continue; }
                            sql += trigger.sql + ";\r\n";
                        }
                    }

                    sql += "-- END TABLE " + table.tbl_name + " --\r\n\r\n";
                    //TableSql.Add(sql);
                }

                return sql;
            }
        }
    }
}