//! Query Builder
//!
//! The QueryBuilder creates sql queries from chained methods
use std::any::Any;
use std::collections::HashMap;

use crate::drivers::{DatabaseDriver, DefaultDriver};
use crate::fns::split_map_join;

use regex::Regex;

/// The position of the wildcard(s)
/// for a `like` clause
#[derive(Debug)]
pub enum LikeWildcard {
    /// Wildcard before search term
    /// eg. `%foo`
    Before,

    /// Wildcard after the search term
    /// eg. `foo%`
    After,

    /// Wildcards surrounding the search term
    /// eg. `%foo%`
    Both,
}

/// The type of SQL join
#[derive(Debug)]
pub enum JoinType {
    /// A `CROSS` join
    Cross,
    /// An `INNER` join
    Inner,
    /// An `OUTER` join
    Outer,
    /// A `LEFT (OUTER)` join
    Left,
    /// A `RIGHT (OUTER)` join
    Right,
}

/// The sort direction
#[derive(Debug, PartialEq)]
pub enum OrderDirection {
    /// Sort Ascending
    Asc,
    /// Sort Descending
    Desc,
    /// Random Sort (Not yet implemented!)
    Rand,
}

/// The type of Query Clause
#[derive(Debug, PartialEq)]
enum QueryClauseType {
    /// Ending a parenthetical grouping
    GroupEnd,
    /// Starting a parenthetical grouping
    GroupStart,
    /// A having clause
    Having,
    /// A join clause
    Join,
    /// A like clause
    Like,
    /// A where clause
    Where,
    /// A where in clause
    WhereIn,
}

#[derive(Debug)]
enum QueryType {
    Select,
    Insert,
    Update,
    Delete,
}

/// QueryBuilder for general SQL queries
///
/// ```
/// use stringqb::prelude::*;
///
/// // You probably do not want to use the default driver, as it
/// // is basically a mock for testing
/// use stringqb::drivers::DefaultDriver;
///
/// // The query builder must be mutable to be useful
/// let mut qb = QueryBuilder::new(DefaultDriver::new());
///
/// // Each builder method returns a mutable reference to itself so
/// // the methods are chainable
/// qb.select("field as f")
///     .from("table t")
///     .inner_join("table_two tt", "field2 as ff", "=", "f")
///     .wher("f >", 3);
///
/// // Since they are references, you do not have to chain.
/// let sql = qb.get_compiled_select();
///
/// # assert_eq!(
/// #    sql,
/// #    r#"SELECT "field" AS "f"
/// # FROM "table" "t"
/// # INNER JOIN "table_two" "tt" ON "field2" AS "ff"=f
/// # WHERE "f" > ?"#
/// # );
/// ```
pub struct QueryBuilder {
    /// The struct to store the query builder info
    state: QueryState,
    driver: Box<dyn DatabaseDriver>,
}

/// The struct representing a prepared statement
pub struct Prepared {}

impl Default for QueryBuilder {
    /// Creates a new QueryBuilder instance with default driver
    ///
    /// This is **not** useful for a real database.
    fn default() -> Self {
        QueryBuilder {
            state: QueryState::new(),
            driver: Box::new(DefaultDriver::new()),
        }
    }
}

impl QueryBuilder {
    /// Create a new QueryBuilder instance with a driver
    ///
    /// ```no_run
    /// use stringqb::prelude::*;
    ///
    /// // Postgres Driver (If enabled)
    /// let pgDriver = PostgresDriver::new("postgres://user:pass@host:port/database");
    ///
    /// // MySQL/MariaDB Driver, requires "mysql" feature
    /// let myDriver = MySQLDriver::new("mysql://user:pass@host:port/database");
    ///
    /// // SQLite Driver (memory), requires "sqlite" feature
    /// #[cfg(feature = "sqlite")]
    /// let liteMemoryDriver = SQLiteDriver::new(":memory:");
    ///
    /// // SQLite Driver (file), requires "sqlite" feature
    /// #[cfg(feature = "sqlite")]
    /// let liteDriver = SQLiteDriver::new("/path/to/db.sqlite3");
    ///
    /// // The variable to the query builder must be mutable
    /// let mut queryBuilder = QueryBuilder::new(pgDriver);
    /// ```
    pub fn new(driver: impl DatabaseDriver + 'static) -> Self {
        QueryBuilder {
            state: QueryState::new(),
            driver: Box::new(driver),
        }
    }

    // --------------------------------------------------------------------------
    // ! Select Queries
    // --------------------------------------------------------------------------

    /// Set the fields to select from the database as a string
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // You can also alias field names
    /// qb.select("foo as bar");
    /// ```
    pub fn select(&mut self, fields: &str) -> &mut Self {
        let fields = self.quote_fields(fields);

        self.state.append_select_string(&fields);

        self
    }

    /// Set the fields to select from the database as a Vector
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // You can also alias via a vector of fields
    /// qb.select_vec(vec!["foo as bar", "baz"]);
    /// ```
    pub fn select_vec(&mut self, fields: Vec<&str>) -> &mut Self {
        let fields = fields.join(",");
        self.select(&fields)
    }

    /// Adds the `distinct` keyword to a query
    pub fn distinct(&mut self) -> &mut Self {
        self.state.prepend_select_string(" DISTINCT");

        self
    }

    /// Tell the database to give you query plan info, rather
    /// than a result set
    pub fn explain(&mut self) -> &mut Self {
        self.state.explain = true;

        self
    }

    /// Specify the database table to select from
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // You can specify an alias for the table
    /// qb.from("products p");
    /// ```
    pub fn from(&mut self, table_name: &str) -> &mut Self {
        let from_str = split_map_join(table_name, " ", |s| self.driver.quote_identifier(s));

        self.state.set_from_string(&from_str);

        self
    }

    // --------------------------------------------------------------------------
    // ! 'Like' methods
    // --------------------------------------------------------------------------

    /// Creates a `like` clause in the sql
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Search for a value that ends with "foo"
    /// qb.like("field", String::from("foo"), LikeWildcard::Before);
    ///
    /// // Search for a value that starts with "foo"
    /// qb.like("field", String::from("foo"), LikeWildcard::After);
    ///
    /// // Search for a value that has "foo" in it
    /// qb.like("field", String::from("foo"), LikeWildcard::Both);
    /// ```
    pub fn like(&mut self, field: &str, value: impl Any, position: LikeWildcard) -> &mut Self {
        self._like(field, value, position, "LIKE", "AND")
    }

    /// Generates an `or like` clause
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Search for a value that ends with "foo"
    /// qb.or_like("field", String::from("foo"), LikeWildcard::Before);
    ///
    /// // Search for a value that starts with "foo"
    /// qb.or_like("field", String::from("foo"), LikeWildcard::After);
    ///
    /// // Search for a value that has "foo" in it
    /// qb.or_like("field", String::from("foo"), LikeWildcard::Both);
    /// ```
    pub fn or_like(&mut self, field: &str, value: impl Any, position: LikeWildcard) -> &mut Self {
        self._like(field, value, position, "LIKE", "OR")
    }

    /// Generates a `not like` clause
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Search for a value that does not end with "foo"
    /// qb.not_like("field", String::from("foo"), LikeWildcard::Before);
    ///
    /// // Search for a value that does not start with "foo"
    /// qb.not_like("field", String::from("foo"), LikeWildcard::After);
    ///
    /// // Search for a value that does not have "foo" in it
    /// qb.not_like("field", String::from("foo"), LikeWildcard::Both);
    /// ```
    pub fn not_like(&mut self, field: &str, value: impl Any, position: LikeWildcard) -> &mut Self {
        self._like(field, value, position, "NOT LIKE", "AND")
    }

    /// Generates an OR NOT Like clause
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Search for a value that does not end with "foo"
    /// qb.or_not_like("field", String::from("foo"), LikeWildcard::Before);
    ///
    /// // Search for a value that does not start with "foo"
    /// qb.or_not_like("field", String::from("foo"), LikeWildcard::After);
    ///
    /// // Search for a value that does not have "foo" in it
    /// qb.or_not_like("field", String::from("foo"), LikeWildcard::Both);
    /// ```
    pub fn or_not_like(
        &mut self,
        field: &str,
        value: impl Any,
        position: LikeWildcard,
    ) -> &mut Self {
        self._like(field, value, position, "NOT LIKE", "OR")
    }

    // --------------------------------------------------------------------------
    // ! Having methods
    // --------------------------------------------------------------------------

    /// Add a `having` clause to the query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // By default, key = value
    /// qb.having("key", vec!["value"]);
    ///
    /// // Other operators can be used with a separating space
    /// qb.having("clues >=", vec![4]);
    /// ```
    pub fn having(&mut self, key: &str, value: Vec<impl Any>) -> &mut Self {
        self._having(key, value, "AND")
    }

    /// Add a `having` clause to the query, prefixed with an `or`
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // By default, key = value
    /// qb.or_having("key", vec!["value"]);
    ///
    /// // Other operators can be used with a separating space
    /// qb.or_having("clues <", vec![88]);
    /// ```
    pub fn or_having(&mut self, key: &str, value: Vec<impl Any>) -> &mut Self {
        self._having(key, value, "OR")
    }

    // --------------------------------------------------------------------------
    // ! 'Where' methods
    // --------------------------------------------------------------------------

    /// Specify a condition for the `where` clause of the query. Can be called
    /// multiple times, which will then add additional where conditions, prefixed
    /// with 'AND'.
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // By default, key = value
    /// qb.r#where("key", "value");
    ///
    /// // Other operators can be used with a separating space
    /// qb.r#where("key >", 4);
    ///
    /// // If you don't like the r#where syntax, you can use the wher method instead
    /// qb.wher("key >", 4);
    /// ```
    pub fn r#where(&mut self, key: &str, value: impl Any) -> &mut Self {
        self._where_string(key, value, "AND")
    }

    /// Alias method for `where`, as using the `where` method requires
    /// using the raw identifier `r#where`.
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // By default, key = value
    /// qb.wher("key", "value");
    ///
    /// // Other operators can be used with a separating space
    /// qb.wher("key >", 4);
    /// ```
    pub fn wher(&mut self, key: &str, value: impl Any) -> &mut Self {
        self._where_string(key, value, "AND")
    }

    /// Specify a condition for the `where` clause of the query, prefixed with `or`
    ///
    /// By default does not have any query grouping.
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // By default, key = value
    /// qb.or_where("key", "value");
    ///
    /// // Other operators can be used with a separating space
    /// qb.or_where("key !=", "foo");
    /// ```
    pub fn or_where(&mut self, key: &str, value: impl Any) -> &mut Self {
        self._where_string(key, value, "OR")
    }

    /// Specify a `where in` clause for the query. If called multiple times,
    /// will prefix the clause with `AND`
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Look for a set of rows matching the values passed
    /// qb.where_in("key", vec![1,2,3]);
    /// ```
    pub fn where_in(&mut self, key: &str, values: Vec<impl Any>) -> &mut Self {
        self._where_in(key, values, "IN", "AND")
    }

    /// Specify a `where in` clause for the query, prefixed with `or`
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Look for a set of rows matching the values passed
    /// qb.or_where_in("key", vec![1,2,3]);
    /// ```
    pub fn or_where_in(&mut self, key: &str, values: Vec<impl Any>) -> &mut Self {
        self._where_in(key, values, "IN", "OR")
    }

    /// Specify a `where not in` clause for the query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Look for a set of rows not matching the values passed
    /// qb.where_not_in("key", vec![1,2,3]);
    /// ```
    pub fn where_not_in(&mut self, key: &str, values: Vec<impl Any>) -> &mut Self {
        self._where_in(key, values, "NOT IN", "AND")
    }

    /// Specify a `where not in` clause for the query, prefixed with `or`
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Look for a set of rows not matching the values passed
    /// qb.or_where_not_in("key", vec![1,2,3]);
    /// ```
    pub fn or_where_not_in(&mut self, key: &str, values: Vec<impl Any>) -> &mut Self {
        self._where_in(key, values, "NOT IN", "OR")
    }

    // --------------------------------------------------------------------------
    // ! Other Query Modifier methods
    // --------------------------------------------------------------------------

    /// Set a key and value for an insert or update query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Can be called multiple times to set multiple values
    /// qb.set("foo", 3)
    ///     .set("bar", 4)
    ///     .insert("table");
    /// ```
    pub fn set(&mut self, key: &str, value: impl Any) -> &mut Self {
        let key = self.driver.quote_identifier(key);
        self.state
            .append_set_array_keys(&key)
            .append_values(Box::new(value));

        self
    }

    /// Set a map of data for an insert or update query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// use std::collections::HashMap;
    ///
    /// let mut authors = HashMap::new();
    /// authors.insert(String::from("Chinua Achebe"), String::from("Nigeria"));
    /// authors.insert(String::from("Rabindranath Tagore"), String::from("India"));
    /// authors.insert(String::from("Anita Nair"), String::from("India"));
    ///
    /// qb.set_map(authors)
    ///     .insert("authors");
    /// ```
    pub fn set_map(&mut self, data: HashMap<String, impl Any>) -> &mut Self {
        for (key, value) in data {
            self.set(&key, value);
        }

        self
    }

    /// Convenience method for a `left` join
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Note that the value is not prepared/escaped, due to it often being a column
    /// qb.left_join("table1", "column1", "<>", "foo");
    /// ```
    pub fn left_join(&mut self, table: &str, col: &str, op: &str, value: &str) -> &mut Self {
        self.join(table, col, op, value, JoinType::Left)
    }

    /// Convenience method for an `inner` join
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Note that the value is not prepared/escaped, due to it often being a column
    /// qb.inner_join("table1", "column1", "<>", "foo");
    /// ```
    pub fn inner_join(&mut self, table: &str, col: &str, op: &str, value: &str) -> &mut Self {
        self.join(table, col, op, value, JoinType::Inner)
    }

    /// Add a table join to the query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // Note that the value is not prepared/escaped, due to it often being a column
    /// qb.join("table1", "column1", "<>", "foo", JoinType::Inner);
    /// ```
    pub fn join(
        &mut self,
        table: &str,
        col: &str,
        op: &str,
        value: &str,
        join_type: JoinType,
    ) -> &mut Self {
        let col = self.quote_fields(col);
        let table = self.quote_table(table);

        let condition = format!(
            "{} ON {}{}{}",
            table,
            &col,
            op,
            value
        );

        let join_type = match join_type {
            JoinType::Cross => "CROSS ",
            JoinType::Left => "LEFT ",
            JoinType::Inner => "INNER ",
            JoinType::Outer => "OUTER ",
            JoinType::Right => "RIGHT ",
        };

        let conjunction = "\n".to_string() + join_type + "JOIN ";

        self.state
            .append_query_map(QueryClauseType::Join, &conjunction, &condition);

        self
    }

    /// Add a group by clause to the query
    pub fn group_by(&mut self, field: &str) -> &mut Self {
        self.state.append_group_array(field);

        let group_string = String::from(" GROUP BY ") + &self.state.get_group_array().join(",");

        self.state.set_group_string(&group_string);

        self
    }

    /// Add an order by clause to the query
    pub fn order_by(&mut self, field: &str, direction: OrderDirection) -> &mut Self {
        let field = self.driver.quote_identifier(field);
        let dir = match direction {
            OrderDirection::Asc => String::from("ASC"),
            OrderDirection::Desc => String::from("DESC"),
            OrderDirection::Rand => self.driver.random(),
        };
        self.state.append_order_map(&field, &dir);

        let mut order_clauses: Vec<String> = vec![];

        for (f, dir) in self.state.get_order_map() {
            let clause = String::clone(f) + " " + &dir;
            &order_clauses.push(clause);
        }

        let order_str = "\nORDER BY ".to_string() + &order_clauses.join(", ");

        self.state.set_order_string(&order_str);

        self
    }

    /// Add a limit to the query
    pub fn limit(&mut self, limit: usize) -> &mut Self {
        self.state.limit = Some(limit);

        self
    }

    ///  Add an offset to the query
    pub fn offset(&mut self, offset: usize) -> &mut Self {
        assert!(
            self.state.offset.is_some(),
            "You must set a limit to set an offset"
        );

        self.state.offset = Some(offset);

        self
    }

    // --------------------------------------------------------------------------
    // ! Query Grouping Methods
    // --------------------------------------------------------------------------

    /// Start a logical grouping in the current query
    pub fn group_start(&mut self) -> &mut Self {
        let conj = if ! self.state.has_where_clause() {
            "\nWHERE "
        } else {
            " "
        };

        self.state
            .append_query_map(QueryClauseType::GroupStart, conj, "(");

        self
    }

    /// Start a logical grouping, prefixed with `not`
    pub fn not_group_start(&mut self) -> &mut Self {
        let conj = if ! self.state.has_where_clause() {
            "\nWHERE "
        } else {
            " AND "
        };

        self.state
            .append_query_map(QueryClauseType::GroupStart, conj, "NOT (");

        self
    }

    /// Start a logical grouping, prefixed with `or`
    pub fn or_group_start(&mut self) -> &mut Self {
        self.state
            .append_query_map(QueryClauseType::GroupStart, "", " OR (");

        self
    }

    /// Start a logical grouping, prefixed with `or not`
    pub fn or_not_group_start(&mut self) -> &mut Self {
        self.state
            .append_query_map(QueryClauseType::GroupStart, "", " OR NOT (");

        self
    }

    /// End the current logical grouping
    pub fn group_end(&mut self) -> &mut Self {
        self.state
            .append_query_map(QueryClauseType::GroupEnd, "", ")");

        self
    }

    // --------------------------------------------------------------------------
    // ! Query execution methods
    // --------------------------------------------------------------------------

    /// Execute the generated select query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // The get() method actually calls the driver to run
    /// // the SQL query
    /// let query = qb.select_vec(vec!["foo", "bar"])
    ///     .from("table t")
    ///     .get();
    /// ```
    pub fn get(&mut self) {
        let sql = self.get_compiled_select();

        self.run(&sql)
    }

    /// Count all the rows in the specified database table
    pub fn count_all(self, table: &str) -> usize {
        unimplemented!();
    }

    /// Execute the generated insert query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // The insert() method actually calls the driver to run
    /// // the SQL query
    /// let query = qb.set("foo", 3)
    ///     .insert("table");
    /// ```
    pub fn insert(&mut self, table: &str) {
        let sql = self.get_compiled_insert(table);

        self.run(&sql)
    }

    /// Execute the generated update query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // The update() method actually calls the driver to run
    /// // the SQL query
    /// let query = qb.set("foo", 3)
    ///     .wher("foo", 4)
    ///     .update("table");
    /// ```
    pub fn update(&mut self, table: &str) {
        let sql = self.get_compiled_update(table);

        self.run(&sql)
    }

    /// Execute the generated delete query
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// // The delete() method actually calls the driver to run
    /// // the SQL query
    /// let query = qb.wher("foo", 3)
    ///     .delete("table");
    /// ```
    pub fn delete(&mut self, table: &str) {
        let sql = self.get_compiled_delete(table);

        self.run(&sql)
    }

    /// Empty the table of all values
    ///
    /// ```no_run
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// let query = qb.truncate("table");
    /// ```
    pub fn truncate(&mut self, table: &str) -> Result<Box<dyn Any>, Box<dyn Any>> {
        let sql = self.driver.truncate(table);

        self.basic_query(&sql)
    }

    // --------------------------------------------------------------------------
    // ! SQL Returning Methods
    // --------------------------------------------------------------------------

    /// Get the generated SQL for a select query
    pub fn get_compiled_select(&self) -> String {
        // The table name should already be set from the `from` method
        assert!(
            self.state.get_from_string().len() > 0,
            "You must use the `from` method to set the table name for a select query"
        );

        self.compile(QueryType::Select, "")
    }

    /// Get the generated SQL for an insert query
    pub fn get_compiled_insert(&self, table: &str) -> String {
        // The fields and values to insert must be specified
        assert!(
            self.state.get_set_array_keys().len() > 0,
            "You must use the `set` or `set_map` method to set columns and values to insert"
        );

        self.compile(QueryType::Insert, table)
    }

    /// Get the generated SQL for an update query
    pub fn get_compiled_update(&self, table: &str) -> String {
        // Updates require fields and values
        assert!(
            self.state.get_set_array_keys().len() > 0,
            "You must use the `set` or `set_map` method to set columns and values to update"
        );

        self.compile(QueryType::Update, table)
    }

    /// Get the generated SQL for a delete query
    pub fn get_compiled_delete(&self, table: &str) -> String {
        // Where clause required
        assert!(
            self.state.has_where_clause(),
            "You must specify a where clause for delete. To empty a table, use the `truncate` method."
        );

        self.compile(QueryType::Delete, table)
    }

    // --------------------------------------------------------------------------
    // ! Miscellaneous Methods
    // --------------------------------------------------------------------------

    /// Get a new instance of the query builder
    pub fn reset(&mut self) -> &mut Self {
        self.state = QueryState::new();

        self
    }

    /// Execute an SQL query with no parameters
    pub fn basic_query(&mut self, sql: &str) -> Result<Box<dyn Any>, Box<dyn Any>> {
        self.driver.query(sql)
    }

    /// Prepare an SQL query
    pub fn prepare(&mut self, sql: &str) -> Prepared {
        unimplemented!();
    }

    /// Execute a prepared statement
    pub fn execute(&mut self, stmt: &Prepared, params: &[Box<dyn Any>]) {
        unimplemented!();
    }

    /// Quotes table column(s)/field(s) accounting for 'as' aliases
    ///
    /// ```
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// let fields = "a.b,c as cplus,d.a as x";
    /// let quoted_fields = qb.quote_fields(fields);
    /// let expected = r#""a"."b","c" AS "cplus","d"."a" AS "x""#;
    ///
    /// assert_eq!(quoted_fields, expected);
    /// ```
    pub fn quote_fields(&mut self, fields: &str) -> String {
        lazy_static! {
            static ref RE: Regex = Regex::new(r"(?i) as ").unwrap();
        };

        split_map_join(fields, ",", |s| {
            if !RE.is_match(s) {
                return self.driver.quote_identifier(s.trim());
            }

            // Do a operation similar to split_map_join for the
            // regex matches, quoting each identifier
            RE.split(s)
                .into_iter()
                .map(|p| self.driver.quote_identifier(p))
                .collect::<Vec<String>>()
                .join(" AS ")
        })
    }

    /// Quotes table(s), accounting for aliases
    ///
    /// ```
    /// # use stringqb::prelude::*;
    /// # let mut qb = QueryBuilder::default();
    /// let tables = "a,b.c,d dprime";
    /// let quoted_tables = qb.quote_table(tables);
    /// let expected = r#""a","b"."c","d" "dprime""#;
    ///
    /// assert_eq!(quoted_tables, expected);
    /// ```
    pub fn quote_table(&mut self, table: &str) -> String {
        split_map_join(table, " ", |s| self.driver.quote_identifier(s))
    }

    // --------------------------------------------------------------------------
    // ! Implementation Details
    // --------------------------------------------------------------------------

    fn _like(
        &mut self,
        field: &str,
        value: impl Any,
        position: LikeWildcard,
        like: &str,
        conj: &str,
    ) -> &mut Self {
        let conj = if ! self.state.has_where_clause() {
            "\nWHERE "
        } else {
            conj
        };

        let field = self.driver.quote_identifier(field);

        let like = format!("{} {} ?", field, like);

        let value: Box<dyn Any + 'static> = Box::new(value);
        let string_val = value.downcast_ref::<String>().unwrap();

        let value = match position {
            LikeWildcard::Before => format!("%{}", string_val),
            LikeWildcard::After => format!("{}%s", string_val),
            LikeWildcard::Both => format!("%{}%", string_val),
        };

        self.state
            .append_query_map(QueryClauseType::Like, conj, &like);
        self.state.append_where_values(Box::new(value));

        self
    }

    fn _having(&mut self, key: &str, values: Vec<impl Any>, conj: &str) -> &mut Self {
        let keys = self._where(key, values);

        for k in keys {
            self._having_key(&k, conj);
        }

        self
    }

    fn _having_key(&mut self, key: &str, conj: &str) -> &mut Self {
        let field = key.trim().split(" ").collect::<Vec<&str>>();

        let mut item = self.driver.quote_identifier(field[0]);;

        let item2 = if field.len() == 1 {
            String::from("=?")
        } else {
            format!(" {} ?", &field[1])
        };

        item += &item2;

        self.state.append_having_map(conj, &item);

        self
    }

    fn _where(&mut self, key: &str, values: Vec<impl Any>) -> Vec<String> {
        for x in values {
            self.state.append_where_values(Box::new(x));
        }

        vec![String::from(key)]
    }

    fn _where_in(
        &mut self,
        key: &str,
        values: Vec<impl Any>,
        in_str: &str,
        conj: &str,
    ) -> &mut Self {
        let key = self.driver.quote_identifier(key);
        let placeholders = vec!["?"; values.len()];

        for value in values {
            self.state.append_where_values(Box::new(value));
        }

        let str = format!("{} {} ({}) ", key, in_str, placeholders.join(","));

        let conj = if ! self.state.has_where_clause() {
            "\nWHERE "
        } else {
            conj
        };

        self.state
            .append_query_map(QueryClauseType::WhereIn, conj, &str);

        self
    }

    fn _where_string(&mut self, key: &str, value: impl Any, conj: &str) -> &mut Self {
        let keys = self._where(key, vec![value]);

        for k in keys {
            self._where_string_key(&k, conj);
        }

        self
    }

    fn _where_string_key(&mut self, key: &str, conj: &str) {
        let field = key.trim().split(" ").collect::<Vec<&str>>();

        let last_item = self.state.get_query_map_last();
        let mut item = self.driver.quote_identifier(field[0]);

        let item2 = if field.len() == 1 {
            String::from("=?")
        } else {
            format!(" {} ?", &field[1])
        };

        item += &item2;

        let conj = if self.state.query_map.len() == 0 || ( ! self.state.has_where_clause()) {
            String::from("\nWHERE")
        } else {
            String::from(conj)
        };

        let conj = if last_item.is_some() {
            let last_item = last_item.unwrap();

            match last_item.clause_type {
                QueryClauseType::GroupStart => String::from(""),
                _ => format!("{} ", conj),
            }
        } else {
            format!("{} ", conj)
        };

        self.state
            .append_query_map(QueryClauseType::Where, &conj, &item);
    }

    fn compile(&self, query_type: QueryType, table: &str) -> String {
        // Get the base clause for the query
        let base_sql = self.compile_type(query_type, &self.driver.quote_identifier(table));

        let mut parts = vec![base_sql];

        for clause in self.state.get_query_map() {
            &parts.push(clause.to_string());
        }

        &parts.push(self.state.get_group_string().to_string());
        &parts.push(self.state.get_order_string().to_string());

        for clause in self.state.get_having_map() {
            &parts.push(clause.to_string());
        }

        let mut sql = parts.join("");

        // Add limit/ offset
        sql = self.driver.limit(&sql, self.state.limit, self.state.offset);

        // Handle explain
        if self.state.explain == true {
            self.driver.explain(&sql)
        } else {
            sql
        }
    }

    fn compile_type(&self, query_type: QueryType, table: &str) -> String {
        match query_type {
            QueryType::Select => {
                let from = self.state.get_from_string();
                let select = self.state.get_select_string();

                let sql = format!("SELECT *\nFROM {}", from);

                if select.len() > 0 {
                    sql.replace("*", select)
                } else {
                    sql
                }
            }
            QueryType::Insert => {
                let set_array_keys = self.state.get_set_array_keys();
                let param_count = set_array_keys.len();
                let params = vec!["?"; param_count];

                format!(
                    "INSERT INTO {} ({})\nVALUES({})",
                    table,
                    set_array_keys.join(","),
                    params.join(",")
                )
            }
            QueryType::Update => {
                let set_string = self.state.get_set_string();

                format!("UPDATE {}\nSET {}", table, set_string)
            }
            QueryType::Delete => format!("DELETE FROM {}", table),
        }
    }

    fn run(&mut self, sql: &str) {
        let mut values: Vec<Box<Any>> = vec![];
        values.append(self.state.get_values());
        values.append(self.state.get_where_values());

        // @TODO determine query result type
        // @TODO prepare/execute query, and return result
        let stmt = self.prepare(sql);
        self.execute(&stmt, &values)
    }
}

#[derive(Debug)]
struct QueryClause {
    clause_type: QueryClauseType,
    conjunction: String,
    string: String,
}

impl QueryClause {
    fn new(clause_type: QueryClauseType, conjunction: &str, string: &str) -> Self {
        QueryClause {
            clause_type,
            conjunction: conjunction.to_string(),
            string: string.to_string(),
        }
    }

    fn to_string(&self) -> String {
        format!("{}{}", self.conjunction, self.string)
    }
}

#[derive(Debug)]
struct QueryState {
    pub explain: bool,

    select_string: String,
    from_string: String,
    set_string: String,
    order_string: String,
    group_string: String,

    // Keys for insert/update statement
    set_array_keys: Vec<String>,

    // Order by clause
    order_map: HashMap<String, String>,

    // Group by clause
    group_array: Vec<String>,

    // Values to apply to prepared statements
    values: Vec<Box<Any>>,

    // Values to apply to where clauses in prepared statements
    where_values: Vec<Box<Any>>,

    pub limit: Option<usize>,

    pub offset: Option<usize>,

    // Query components for complex selects
    query_map: Vec<QueryClause>,

    // Query components for having clauses
    having_map: Vec<QueryClause>,
}

impl Default for QueryState {
    fn default() -> Self {
        QueryState {
            explain: false,

            select_string: String::from(""),
            from_string: String::from(""),
            set_string: String::from(""),
            order_string: String::from(""),
            group_string: String::from(""),

            set_array_keys: vec![],
            order_map: HashMap::new(),
            group_array: vec![],
            values: vec![],
            where_values: vec![],

            limit: None,
            offset: None,

            query_map: vec![],
            having_map: vec![],
        }
    }
}

impl QueryState {
    fn new() -> Self {
        QueryState::default()
    }

    fn append_select_string(&mut self, s: &str) -> &mut Self {
        self.select_string += s;

        self
    }

    fn prepend_select_string(&mut self, s: &str) -> &mut Self {
        self.select_string = String::from(s) + &self.select_string;

        self
    }

    fn append_group_array(&mut self, field: &str) -> &mut Self {
        self.group_array.push(String::from(field));

        self
    }

    fn append_having_map(&mut self, conj: &str, s: &str) -> &mut Self {
        let conj = if self.having_map.len() == 0 {
            String::from(" HAVING ")
        } else {
            format!(" {} ", conj)
        };

        self.having_map
            .push(QueryClause::new(QueryClauseType::Having, &conj, s));

        self
    }

    fn append_order_map(&mut self, key: &str, dir: &str) -> &mut Self {
        self.order_map.insert(String::from(key), String::from(dir));

        self
    }

    fn append_set_array_keys(&mut self, key: &str) -> &mut Self {
        self.set_array_keys.push(key.to_string());

        self
    }

    fn append_values(&mut self, val: Box<Any>) -> &mut Self {
        self.values.push(val);

        self
    }

    fn append_where_values(&mut self, val: Box<Any>) -> &mut Self {
        self.where_values.push(val);

        self
    }

    fn append_query_map(&mut self, clause_type: QueryClauseType, conj: &str, s: &str) -> &mut Self {
        self.query_map.push(QueryClause::new(clause_type, conj, s));

        self
    }

    fn get_from_string(&self) -> &str {
        &self.from_string
    }

    fn get_group_array(&self) -> &Vec<String> {
        &self.group_array
    }

    fn get_group_string(&self) -> &str {
        &self.group_string
    }

    fn get_having_map(&self) -> &Vec<QueryClause> {
        &self.having_map
    }

    fn get_query_map(&self) -> &Vec<QueryClause> {
        &self.query_map
    }

    fn get_query_map_last(&self) -> Option<&QueryClause> {
        if self.query_map.len() == 0 {
            return None;
        }

        let index = self.query_map.len() - 1;

        Some(&self.query_map[index])
    }

    fn get_select_string(&self) -> &str {
        &self.select_string
    }

    fn get_set_array_keys(&self) -> &Vec<String> {
        &self.set_array_keys
    }

    fn get_set_string(&self) -> &str {
        &self.set_string
    }

    fn get_order_map(&self) -> &HashMap<String, String> {
        &self.order_map
    }

    fn get_order_string(&self) -> &str {
        &self.order_string
    }

    fn get_values(&mut self) -> &mut Vec<Box<Any>> {
        &mut self.values
    }

    fn get_where_values(&mut self) -> &mut Vec<Box<Any>> {
        &mut self.where_values
    }

    fn has_where_clause(&self) -> bool {
        let has_clause = false;

        for clause in self.query_map.iter() {
            match clause.clause_type {
                QueryClauseType::Where => return true,
                QueryClauseType::WhereIn => return true,
                _ => (),
            }
        }

        has_clause
    }

    fn set_from_string(&mut self, s: &str) -> &mut Self {
        self.from_string = String::from(s);

        self
    }

    fn set_group_string(&mut self, s: &str) -> &mut Self {
        self.group_string = String::from(s);

        self
    }

    fn set_order_string(&mut self, order_string: &str) -> &mut Self {
        self.order_string = String::from(order_string);

        self
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn set_key_value() {
        let mut qb = QueryBuilder::default();

        qb.set("foo", "bar");

        assert_eq!(qb.state.get_set_array_keys()[0], "\"foo\"");
        assert!(qb.state.get_values()[0].is::<&str>());

        // @TODO find a way to make this kind of operation much more ergonomic
        assert_eq!(
            *qb.state.get_values()[0].downcast_ref::<&str>().unwrap(),
            "bar"
        );
    }

    #[test]
    fn set_hashmap() {
        let mut qb = QueryBuilder::default();

        let mut authors = HashMap::new();
        authors.insert(String::from("Chinua Achebe"), String::from("Nigeria"));
        authors.insert(String::from("Rabindranath Tagore"), String::from("India"));
        authors.insert(String::from("Anita Nair"), String::from("India"));

        qb.set_map(authors);

        // assert_eq!(qb.state.set_array_keys[0], "Chinua Achebe");
        assert_eq!(qb.state.get_set_array_keys().len(), 3);
        assert_eq!(qb.state.get_values().len(), 3);
    }

    #[test]
    fn set_where_in() {
        let mut qb = QueryBuilder::default();

        qb.from("test").where_in("foo", vec![0, 1, 2, 3, 4, 5]);

        let sql = qb.get_compiled_select();
        let expected = "SELECT *\nFROM \"test\"\nWHERE \"foo\" IN (?,?,?,?,?,?) ";

        assert_eq!(sql, expected);
    }
}