rustorm 0.0.8

use dao::{Value, ToValue};
use table::{Table};
use std::collections::BTreeMap;
use database::Database;
use dao::DaoResult;
use dao::IsDao;
use dao::Dao;
use table::IsTable;
use writer::SqlFrag;
use std::fmt;

#[derive(Debug)]
#[derive(Clone)]
pub enum JoinType{
    CROSS,
    INNER,
    OUTER,
}
#[derive(Debug)]
#[derive(Clone)]
pub enum Modifier{
    LEFT,
    RIGHT,
    FULL,
}

#[derive(Debug)]
#[derive(Clone)]
pub struct Join{
    pub modifier:Option<Modifier>,
    pub join_type:JoinType,
    pub table_name:TableName,
    pub column1:Vec<String>,
    pub column2:Vec<String>
}
#[derive(Debug)]
#[derive(Clone)]
pub enum Direction{
    ASC,
    DESC,
}


////
/// Filter struct merged to query
/// 
#[derive(Debug)]
#[derive(Clone)]
pub enum Connector{
    And,
    Or
}

#[derive(Debug)]
#[derive(Clone)]
pub enum Equality{
    EQ, //EQUAL,
    NE, //NOT_EQUAL,
    LT, //LESS_THAN,
    LTE, //LESS_THAN_OR_EQUAL,
    GT, //GREATER_THAN,
    GTE, //GREATER_THAN_OR_EQUAL,
    IN,
    NOT_IN,//NOT_IN,
    LIKE,
    NULL,
    IS_NOT_NULL,//NOT_NULL,
    IS_NULL,//IS_NULL,
}

/// function in a sql statement
#[derive(Debug)]
#[derive(Clone)]
pub struct Function{
    pub function:String,
    pub params:Vec<Operand>,
}

/// Operands can be columns, functions, query or value types
#[derive(Debug)]
#[derive(Clone)]
pub enum Operand{
    ColumnName(ColumnName),
    TableName(TableName),
    Function(Function),
    Query(Query),
    Value(Value),
    Vec(Vec<Operand>),
}

/// expression has left operand,
/// equality and right operand
#[derive(Debug)]
#[derive(Clone)]
pub struct Condition{
    pub left:Operand,
    pub equality:Equality,
    pub right:Operand,
}

/// TODO: support for functions on columns
/// TODO: need to merge with Expr
#[derive(Debug)]
#[derive(Clone)]
pub struct Filter{
    pub connector:Connector,
    /// TODO: maybe renamed to LHS, supports functions and SQL
    pub condition: Condition,
    pub subfilters:Vec<Filter>
}

impl Filter{
    
    /// user friendly, commonly use API
    pub fn new(column:&str, equality:Equality, value:&ToValue)->Self{
        let right = Operand::Value(value.to_db_type());
        Filter{
            connector:Connector::And,
            condition: Condition{left: Operand::ColumnName(ColumnName::from_str(column)),
                        equality:equality,
                        right:right},
            subfilters:vec![],
        }
    }
    
    
    /// not very commonly used, offers enough flexibility
    pub fn bare_new(left: Operand, equality: Equality, right: Operand)->Self{
        Filter{
            connector:Connector::And,
            condition: Condition{left:left,
                        equality:equality,
                        right:right},
            subfilters:vec![],
        }
    }
    
    
    pub fn is_null(column:&str)->Self{
        Filter::new(column, Equality::IS_NULL, &())
    }
    pub fn is_not_null(column:&str)->Self{
        Filter::new(column, Equality::IS_NOT_NULL, &())
    }
    
    pub fn and(&mut self, column:&str, equality:Equality, value:&ToValue)->&mut Self{
        let mut filter = Filter::new(column, equality, value);
        filter.connector = Connector::And;
        self.subfilters.push(filter);
        self
    }
    
    pub fn or(&mut self, column:&str, equality:Equality, value:&ToValue)->&mut Self{
        let mut filter = Filter::new(column, equality, value);
        filter.connector = Connector::Or;
        self.subfilters.push(filter);
        self
    }
    
    pub fn or_filter(&mut self, filter: Filter)->&mut Self{
        let mut filter = filter.clone();
        filter.connector = Connector::Or;
        self.subfilters.push(filter);
        self
    }
    pub fn and_filter(&mut self, filter: Filter)->&mut Self{
        let mut filter = filter.clone();
        filter.connector = Connector::And;
        self.subfilters.push(filter);
        self
    }
}

/// Could have been SqlAction
#[derive(Debug)]
#[derive(Clone)]
pub enum SqlType{
    //DML
    SELECT,
    INSERT,
    UPDATE,
    DELETE,
}

#[derive(Clone)]
#[derive(Debug)]
pub struct ColumnName{
    pub column:String,
    pub table:Option<String>,
    ////optional schema, if ever there are same tables resideing in  different schema/namespace
    pub schema:Option<String>,
}

#[derive(Debug)]
#[derive(Clone)]
pub struct Field{
    /// the field
    pub operand:Operand,
    /// when renamed as field
    pub name:Option<String>,
}

impl Field{

    fn rename(&self)->Field{
        match self.operand{
            Operand::ColumnName(ref column_name) => {
                let rename = column_name.default_rename();
                Field{
                    operand:Operand::ColumnName(column_name.clone()), 
                    name:Some(rename)
                }
            },
            _ => panic!("not yet")
        }
    }
}

impl ColumnName{

    pub fn from_str(column:&str)->Self{
        if column.contains("."){
            let splinters = column.split(".").collect::<Vec<&str>>();
            assert!(splinters.len() == 2, "There should only be 2 splinters");
            let table_split = splinters[0].to_string();
            let column_split = splinters[1].to_string();
            ColumnName{
                column:column_split.to_string(), 
                table:Some(table_split.to_string()), 
                schema:None,
            }
        } else {
            ColumnName{
                column:column.to_string(), 
                table:None, 
                schema:None,
            }
        }
    }
    
    fn default_rename(&self)->String{
         if self.table.is_some(){
            return format!("{}_{}", self.table.as_ref().unwrap(), self.column);
        }else{
            panic!("Unable to rename {} since table is not specified", self.column);
        }
    }
    
    /// table name and column name
    pub fn complete_name(&self)->String{
        if self.table.is_some(){
            return format!("{}.{}", self.table.as_ref().unwrap(), self.column);
        }else{
            return self.column.to_string();
        }
    }
    /// includes the schema, table name and column name
    pub fn super_complete_name(&self)->String{
        if self.schema.is_some(){
            return format!("{}.{}", self.schema.as_ref().unwrap(), self.complete_name());
        }else{
            return self.complete_name();
        }
    }
    
    /// is this column conflicts the other column
    /// conflicts means, when used both in a SQL query, it will result to ambiguous columns
    fn is_conflicted(&self, other:&ColumnName)->bool{
        self.column == other.column
    }
}

impl fmt::Display for ColumnName{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.complete_name())
    }
}

impl PartialEq for ColumnName{
    fn eq(&self, other: &Self) -> bool{
        self.column == other.column && self.table == other.table
     }

    fn ne(&self, other: &Self) -> bool {
        self.column != other.column || self.table != other.table || self.schema != other.schema
    }
}


#[derive(Clone)]
#[derive(Debug)]
pub struct TableName{
    pub schema: Option<String>,
    pub name: String,
    /// optional columns needed when rename for conflicting columns are needed
    pub columns: Vec<ColumnName>,
}

impl TableName{
    
    fn from_str(str: &str)->Self{
        if str.contains("."){
            let splinters = str.split(".").collect::<Vec<&str>>();
            assert!(splinters.len() == 2, "There should only be 2 splinters");
            let schema_split = splinters[0].to_string();
            let table_split = splinters[1].to_string();
            
            TableName{
                schema: Some(schema_split),
                name: table_split,
                columns: vec![],
            }
            
        } else {
             TableName{
                schema: None,
                name: str.to_string(),
                columns: vec![],
            }
        }
    }
    
    pub fn complete_name(&self)->String{
        match self.schema{
            Some (ref schema) => format!("{}.{}",schema, self.name),
            None => self.name.to_string()
        }
    }
}

impl PartialEq for TableName{
    fn eq(&self, other: &Self) -> bool{
        self.name == other.name && self.schema == other.schema
     }

    fn ne(&self, other: &Self) -> bool {
        self.name != other.name || self.schema != other.schema
    }
}

impl fmt::Display for TableName{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.complete_name())
    }
}

/// convert str, IsTable to TableName
pub trait ToTableName{
    
    fn to_table_name(&self)->TableName;
    
}

impl <'a>ToTableName for &'a str{
    
    fn to_table_name(&self)->TableName{
        TableName::from_str(self)
    }
}


impl ToTableName for Table{
    
    /// contain the columns for later use when renaming is necessary
    fn to_table_name(&self)->TableName{
        let mut columns = vec![];
        for c in &self.columns{
            let column_name = ColumnName{
                schema: Some(self.schema.to_string()), 
                table: Some(self.name.to_string()), 
                column: c.name.to_string(), 
            };
            columns.push(column_name);
        }
        TableName{
            schema:Some(self.schema.to_string()),
            name: self.name.to_string(),
            columns: columns,
        }
    }
}

/// Query Error
pub enum Error{
    NoTableSpecified(String),
    NoColumnSpecified(String),
    SqlError(String),
}

#[derive(Debug)]
#[derive(Clone)]
pub struct Query{
    
    ///sql type determine which type of query to form, some fields are not applicable to other types of query
    pub sql_type:SqlType,
    
    /// whether to select the records distinct
    pub distinct: bool,
    
    /// whether to enumate all columns in involved models
    pub enumerate_all: bool,
    
    pub declared_query: BTreeMap<String, Query>,

    ///fields can be functions, column sql query, and even columns
    /// TODO; merge enumerated column to this, add a builder for fields
    pub enumerated_fields:Vec<Field>,
    
    /// specify to use distinct ON set of columns 
    pub distinct_on_columns:Vec<String>,
    
    /// filter records, ~ where statement of the query
    pub filters:Vec<Filter>,
    
    /// joining multiple tables
    pub joins:Vec<Join>,
    
    /// ordering of the records via the columns specified
    pub order_by:Vec<(String, Direction)>,
    
    /// grouping columns to create an aggregate
    pub group_by: Vec<Operand>,
    
    /// having field
    pub having: Vec<Condition>,
    
    /// exclude the mention of the columns in the SQL query, useful when ignoring changes in update/insert records
    pub excluded_columns:Vec<ColumnName>,
    
    /// paging of records
    pub page:Option<usize>,
    
    /// size of a page
    pub page_size:Option<usize>,
    
    /// where the focus of values of column selection
    /// this is the table to insert to, update to delete, create, drop
    /// whe used in select, this is the 
    /// pub from_table:Option<TableName>,
    
    /// from field, where field can be a query, table, column, or function
    pub from:Option<Box<Field>>,
    
    /// The data values, used in bulk inserting, updating,
    pub values:Vec<Operand>,
    
    /// the returning clause of the query when supported,
    pub enumerated_returns: Vec<Field>,
}

impl Query{
    
    /// the default query is select
    pub fn new()->Self{
        Query{
            sql_type:SqlType::SELECT,
            distinct:false,
            enumerate_all: false,
            declared_query: BTreeMap::new(),
            enumerated_fields: vec![],
            distinct_on_columns: vec![],
            filters: vec![],
            joins: vec![],
            order_by: vec![],
            group_by: vec![],
            having: vec![],
            excluded_columns:vec![],
            page:None,
            page_size:None,
            from: None,
            values:vec![],
            enumerated_returns: vec![],
        }
    }
    
    pub fn select()->Self{
        let mut q = Query::new();
        q.sql_type = SqlType::SELECT;
        q
    }
    
    pub fn insert()->Self{
        let mut q = Query::new();
        q.sql_type = SqlType::INSERT;
        q
    }
    pub fn update()->Self{
        let mut q = Query::new();
        q.sql_type = SqlType::UPDATE;
        q
    }
    pub fn delete()->Self{
        let mut q = Query::new();
        q.sql_type = SqlType::DELETE;
        q
    }
    
    /// add DISTINCT ie: SELECT DISTINCT
    pub fn distinct(&mut self)->&mut Self{
        self.distinct = true;
        self
    }
    
    pub fn select_all()->Self{
        let mut q = Self::select();
        q.all();
        q
    }
    pub fn enumerate_all()->Self{
        let mut q = Self::select();
        q.enumerate_all = true;
        q
    }
    
    pub fn all(&mut self)->&mut Self{
        self.column("*")
    }
    
    fn enumerate(&mut self, column_name: ColumnName)->&mut Self{
        let operand = Operand::ColumnName(column_name);
        let field = Field{operand:operand, name:None};
        self.enumerated_fields.push(field);
        self
    }
    
    /// all enumerated columns shall be called from this
    /// any conflict of columns from some other table will be automatically renamed
    /// columns that are not conflicts from some other table,
    /// but is the other conflicting column is not explicityly enumerated will not be renamed
    /// 
    pub fn column(&mut self, column:&str)->&mut Self{
        let column_name = ColumnName::from_str(column);
        self.enumerate(column_name);
        self
    }
    
    
    pub fn columns(&mut self, columns:Vec<&str>)->&mut Self{
        for c in columns{
            self.column(c);
        }
        self
    }
    
    pub fn group_by(&mut self, columns:Vec<&str>)->&mut Self{
        for c in columns{
            let column_name = ColumnName::from_str(c);
            let operand = Operand::ColumnName(column_name);
            self.group_by.push(operand);
        }
        self
    }
    
    pub fn having(&mut self, column:&str, equality: Equality, value :&ToValue)->&mut Self{
        let column_name = ColumnName::from_str(column);
        let left = Operand::ColumnName(column_name);
        let cond = Condition{
            left: left,
            equality: equality,
            right: Operand::Value(value.to_db_type())
        };
        self.having.push(cond);
        self
    }
    
    /// exclude columns when inserting/updating data
    /// also ignores the column when selecting records
    /// useful for manipulating thin records by excluding huge binary blobs such as images
    pub fn exclude_column(&mut self, column:&str)->&mut Self{
        let c = ColumnName::from_str(column);
        self.excluded_columns.push(c);
        self
    }
    pub fn exclude_columns(&mut self, columns:Vec<&str>)->&mut Self{
        for c in columns{
            self.exclude_column(c);
        }
        self
    }
    
    pub fn distinct_on_columns(&mut self, columns:&Vec<String>)->&mut Self{
        let columns = columns.clone();
        for c in columns{
            self.distinct_on_columns.push(c);
        }
        self
    }
    
    /// when paging multiple records
    pub fn set_page(&mut self, page:usize)->&mut Self{
        self.page = Some(page);
        self
    }
    
    /// the number of items retrieve per page
    pub fn set_page_size(&mut self, items:usize)->&mut Self{
        self.page_size = Some(items);
        self
    }

    /// the number of items retrieve per page
    pub fn limit(&mut self, limit:usize)->&mut Self{
        self.set_page_size(limit)
    }
    
    /// A more terse way to write the query
    pub fn from(&mut self, table: &ToTableName)->&mut Self{
        let table_name = table.to_table_name();
        let operand = Operand::TableName(table_name);
        let field = Field{ operand:operand, name: None};
        self.from_field(field)
    }
    
     pub fn from_table(&mut self, table:&str)->&mut Self{
        self.from(&table)
    }
    /// `into` is used in rust, os settled with `into_`
    pub fn into_(&mut self, table :&ToTableName)->&mut Self{
        self.sql_type = SqlType::INSERT;
        self.from(table)
    }
    /// can not use into since it's rust .into built-in (owned)
    pub fn into_table(&mut self, table: &str)->&mut Self{
        self.into_(&table)
    }
    /// can be used in behalf of into_, from, 
    pub fn table(&mut self, table: &ToTableName)->&mut Self{
        self.from(table)
    }
    
    /// if the database support CTE declareted query i.e WITH, 
    /// then this query will be declared
    /// if database doesn't support WITH queries, then this query will be 
    /// wrapped in the from_query
    /// build a builder for this
    pub fn declare_query(&mut self, query:Query, alias:&str)->&mut Self{
        self.declared_query.insert(alias.to_string(), query);
        self
    }
    
    /// a query to query from
    /// use WITH (query) t1 SELECT from t1 declaration in postgresql, sqlite
    /// use SELECT FROM (query) in oracle, mysql, others 
    /// alias of the table
    pub fn from_query(&mut self, query:Query, alias:&str)->&mut Self{
        let operand = Operand::Query(query);
        let field = Field{operand:operand, name:Some(alias.to_string())};
        self.from_field(field)
    }
    
    pub fn from_field(&mut self, field:Field)->&mut Self{
        self.from = Some(Box::new(field));
        self
    }
    
    pub fn get_from_table(&self)->Option<&TableName>{
        match self.from{
            Some(ref field) => {
                match field.operand{
                    Operand::TableName(ref table_name) => {
                        Some(table_name)
                     },
                    _ => None
                }
            },
            None => None,
        }
    }
    
    
    /// join a table on this query
    ///
    pub fn join(&mut self, join:Join)->&mut Self{
        self.joins.push(join);
        self
    }
    
    
    /// join a table on this query
    ///
    pub fn left_join_table(&mut self, table:&str, column1:&str, column2:&str)->&mut Self{
        self.left_join(&table, column1, column2)
    }
    pub fn left_join(&mut self, table:&ToTableName, column1:&str, column2:&str)->&mut Self{
        let join = Join{
            modifier:Some(Modifier::LEFT),
            join_type:JoinType::OUTER,
            table_name: table.to_table_name(),
            column1:vec![column1.to_string()],
            column2:vec![column2.to_string()]
        };
        self.join(join)
    }
    pub fn right_join_table(&mut self, table:&str, column1:&str, column2:&str)->&mut Self{
        self.right_join(&table, column1, column2)
    }
    pub fn right_join(&mut self, table:&ToTableName, column1:&str, column2:&str)->&mut Self{
        let join = Join{
            modifier:Some(Modifier::RIGHT),
            join_type:JoinType::OUTER,
            table_name: table.to_table_name(),
            column1:vec![column1.to_string()],
            column2:vec![column2.to_string()]
        };
        self.join(join)
    }
    pub fn full_join_table(&mut self, table:&str, column1:&str, column2:&str)->&mut Self{
        self.full_join(&table, column1, column2)
    }
    pub fn full_join(&mut self, table:&ToTableName, column1:&str, column2:&str)->&mut Self{
        let join = Join{
            modifier:Some(Modifier::FULL),
            join_type:JoinType::OUTER,
            table_name: table.to_table_name(),
            column1:vec![column1.to_string()],
            column2:vec![column2.to_string()]
        };
        self.join(join)
    }
    
    pub fn inner_join_table(&mut self, table:&str, column1:&str, column2:&str)->&mut Self{
        self.inner_join(&table, column1, column2)
    }
    pub fn inner_join(&mut self, table:&ToTableName, column1:&str, column2:&str)->&mut Self{
        let join  = Join{
            modifier:None,
            join_type:JoinType::INNER,
            table_name: table.to_table_name(),
            column1:vec![column1.to_string()],
            column2:vec![column2.to_string()]
        };
        self.join(join)
    }
    
    ///ascending orderby of this column
    pub fn asc(&mut self, column:&str)->&mut Self{
        self.order_by.push((column.to_string(), Direction::ASC));
        self
    }
        ///ascending orderby of this column
    pub fn desc(&mut self, column:&str)->&mut Self{
        self.order_by.push((column.to_string(), Direction::DESC));
        self
    }
    
    /// get the indexes of the fields that matches the the column name
    fn match_fields_indexes(&self, column: &str)->Vec<usize>{
        let mut indexes = vec![];
        let mut cnt = 0;
        for field in &self.enumerated_fields{
            match field.operand{
                Operand::ColumnName(ref column_name) => {
                    if column_name.column == column{
                        indexes.push(cnt);
                    }
                },
                _ => {},
            }
            cnt += 1;
        }
        indexes
    }
    
    /// take the enumerated field that is a column that matched the name
    fn rename_fields(&mut self, column:&str)->&mut Self{
        let matched_indexes = self.match_fields_indexes(column);
        for index in matched_indexes{
            let field = self.enumerated_fields.remove(index);//remove it
            let field = field.rename(); //rename it
            self.enumerated_fields.insert(index, field); //insert it back to the same location
        }
        self
    }
    
    pub fn get_involved_tables(&self)->Vec<TableName>{
        let mut tables = vec![];
        let from_table = self.get_from_table();
        if from_table.is_some(){
            tables.push(from_table.unwrap().clone());
        }
        for j in &self.joins{
            if !tables.contains(&&j.table_name){
                tables.push(j.table_name.clone());
            }
        }
        tables
    }
    
    /// preprocess the missing fields of the query,
    /// such as mentioning the columns of the from_table
    /// enumerate the columns of the involved tables
    /// skipping those which are explicitly ignored
    /// the query will then be built and ready to be executed
    /// TODO: renamed conflicting enumerated columns
    /// if no enumerated fields and no excluded columns
    /// do a select all
    pub fn finalize(&mut self)->&Self{
        
        let involved_models = self.get_involved_tables();
        if involved_models.len() > 1{
            //enumerate all columns when there is a join
            if self.enumerate_all{
                self.enumerate_involved_tables_columns(&involved_models);
            }
            self.rename_conflicting_columns(); // rename an enumerated columns that conflicts
        }
        let excluded_columns = &self.excluded_columns.clone();
        for i in  excluded_columns{
            self.remove_from_enumerated(&i);
        }
        if self.excluded_columns.is_empty() 
            && self.enumerated_fields.is_empty(){
            self.all();
        }
        self
    }
    
    fn enumerate_involved_tables_columns(&mut self, involved_models:&Vec<TableName>){
        for m in involved_models{
            for c in &m.columns{
                self.enumerate(c.clone());
            }
        }
    }
    
    fn get_renamed_fields(&self)->Vec<&Field>{
        let mut renamed = vec![];
        for field in &self.enumerated_fields{
            if field.name.is_some(){
                renamed.push(field);
            }
        }
        renamed
    }
    
    /// return the list of renamed columns, used in dao conversion to struc types
    pub fn get_renamed_columns(&self)->Vec<(ColumnName, String)>{
        let mut renamed_columns = vec![];
        let renamed_fields = self.get_renamed_fields();
        for field in &renamed_fields{
            match field.operand{
                Operand::ColumnName(ref column_name) => {
                    if field.name.is_some(){
                        let rename = field.name.as_ref().unwrap().to_string();
                        renamed_columns.push( (column_name.clone(), rename ) );
                    }
                },
                _ => ()
            }
        }
        renamed_columns
    }
    
    /// determine which columns are conflicting and rename it accordingly
    /// rename only the columns that are in the enumerated list
    fn get_conflicting_columns(&self)->Vec<String>{
        let mut conflicts = vec![];
        let enumerated_columns = self.get_enumerated_columns();
        for c in &enumerated_columns{
            for d in &enumerated_columns{
                if c != d {
                    if c.is_conflicted(d){
                        conflicts.push(c.column.to_string());
                    }
                }
            }
        }
        conflicts
    }
    /// rename the fields that has a conflicting column
    fn rename_conflicting_columns(&mut self)->&mut Self{
        let conflicts = self.get_conflicting_columns();
        for c in conflicts{
            self.rename_fields(&c);
        }
        self
    }
    
    /// used by removed_from_enumerated
    fn index_of_field(&self, column: &ColumnName)->Option<usize>{
        let mut cnt = 0;
        for field in &self.enumerated_fields{
            match field.operand{
                Operand::ColumnName(ref column_name) => {
                    if column_name == column{
                        return Some(cnt);
                    }
                },
                _ => {},
            }
            cnt += 1;
        }
        None
    }
    
    fn remove_from_enumerated(&mut self, column_name: &ColumnName)->&mut Self{
        let index = self.index_of_field(column_name);
        if index.is_some(){
            self.enumerated_fields.remove(index.unwrap());
        }
        self
    }
    
    /// return the list of enumerated columns
    /// will be used for updating records
    pub fn get_enumerated_columns(&self)->Vec<&ColumnName>{
        let mut columns = vec![];
        for field in &self.enumerated_fields{
            match field.operand{
                Operand::ColumnName(ref column_name) => {
                      columns.push(column_name);
                },
                _ => {},
            }
        }
        columns
    }
    
    
    pub fn add_filter(&mut self, filter:Filter)->&mut Self{
        self.filters.push(filter);
        self
    }
    
    pub fn filter(&mut self, column:&str, equality:Equality, value:&ToValue)->&mut Self{
        self.add_filter(Filter::new(column, equality, value))
    }
    
    pub fn add_value(&mut self, value:Operand)->&mut Self{
        self.values.push(value);
        self
    }
    
    pub fn value(&mut self, value:&ToValue)->&mut Self{
        let operand = Operand::Value(value.to_db_type());
        self.add_value(operand)
    }
    
    /// set a value of a column when inserting/updating records
    pub fn set(&mut self, column: &str, value:&ToValue)->&mut Self{
        self.column(column);
        self.value(value)
    }
    
     pub fn return_all(&mut self)->&mut Self{
        self.enumerate_column_as_return("*")
    }
    
    pub fn returns(&mut self, columns: Vec<&str>)->&mut Self{
        for c in columns{
            self.enumerate_column_as_return(c);
        }
        self
    }
    
    pub fn enumerate_column_as_return(&mut self, column:&str)->&mut Self{
        let column_name = ColumnName::from_str(column);
        let operand = Operand::ColumnName(column_name);
        let field = Field{operand: operand, name:None};
        self.enumerated_returns.push(field);
        self
    }
    
    /// build the query only, not executed, useful when debugging
    pub fn build(&mut self, db: &mut Database)->SqlFrag{
        self.finalize();
        db.build_query(self)
    }
    
    /// expects a return, such as select, insert/update with returning clause
    pub fn execute_with_return(&mut self, db: &mut Database)->DaoResult{
        self.finalize();
        db.execute_with_return(self)
    }
    
    /// expects a return, such as select, insert/update with returning clause
    /// no casting of data to structs is done
    /// This is used when retrieving multiple models in 1 query, then casting the records to its equivalent structs
    pub fn execute_with_one_return(&mut self, db: &mut Database)->Dao{
        self.finalize();
        db.execute_with_one_return(self)
    }
    
    /// delete, update without caring for the return
    pub fn execute(&mut self, db: &mut Database)->Result<usize, String>{
        self.finalize();
        db.execute(self)
    }
    
    /// execute the query, then convert the result
    pub fn collect<T: IsDao+IsTable>(&mut self, db: &mut Database)->Vec<T>{
        let result = self.execute_with_return(db);
        result.cast()
    }
    
    /// execute the query then collect only 1 record
    /// TODO: use Result<T,Error> instead of Option<T>
    pub fn collect_one<T: IsDao+IsTable>(&mut self, db: &mut Database)->Option<T>{
        let result = self.execute_with_return(db);
        result.cast_one()
    }
}