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

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

/// 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 {
    /// An `INNER` join
    Inner,
    /// An `OUTER` join
    Outer,
    /// A `LEFT` join
    Left,
    /// A `RIGHT` join
    Right,
    /// A `LEFT OUTER` join
    LeftOuter,
    /// A `RIGHT OUTER` join
    RightOuter,
}

/// The sort direction
#[derive(Debug, PartialEq)]
pub enum OrderDirection {
    /// Sort Ascending
    Asc,
    /// Sort Descending
    Desc,
    /// Random Sort
    Rand,
}

#[derive(Debug)]
enum QueryClauseType {
    GroupEnd,
    GroupStart,
    Join,
    Like,
    Where,
    WhereIn,
}

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

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

#[derive(Debug)]
struct QueryState {
    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_array: HashMap<String, String>,

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

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

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

    limit: Option<usize>,

    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 {
            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_array: HashMap::new(),
            group_array: vec![],
            values: vec![],
            where_values: vec![],

            limit: None,
            offset: None,

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

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

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

        self
    }

    pub 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
    }

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

        self
    }
}

/// The struct representing a query builder
#[derive(Debug)]
pub struct QueryBuilder {
    state: QueryState,
    driver: Box<dyn DatabaseDriver>,
}

impl Default for QueryBuilder {
    /// Creates a new QueryBuilder instance with default driver
    fn default() -> Self {
        QueryBuilder {
            state: QueryState::new(),
            driver: Box::new(DefaultDriver::new()),
        }
    }
}

impl QueryBuilder {
    /// Create a new QueryBuilder instance with a driver
    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
    pub fn select(&mut self, fields: &str) -> &mut Self {
        unimplemented!();
    }

    /// Set the fields to select from the database as a Vector
    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 {
        unimplemented!();
    }

    /// Specify the database table to select from
    pub fn from(&mut self, table_name: &str) -> &mut Self {
        // @TODO properly escape the table name
        self.state.from_string = table_name.to_string();

        self
    }

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

    /// Creates a `like` clause in the sql statement
    pub fn like(&mut self, field: &str, value: Box<dyn Any>, position: LikeWildcard) -> &mut Self {
        unimplemented!();
    }

    /// Generates an OR Like clause
    pub fn or_like(
        &mut self,
        field: &str,
        value: Box<dyn Any>,
        position: LikeWildcard,
    ) -> &mut Self {
        unimplemented!();
    }

    /// Generates a NOI Like clause
    pub fn not_like(
        &mut self,
        field: &str,
        value: Box<dyn Any>,
        position: LikeWildcard,
    ) -> &mut Self {
        unimplemented!();
    }

    /// Generates an OR NOT Like clause
    pub fn or_not_like(
        &mut self,
        field: &str,
        value: Box<dyn Any>,
        position: LikeWildcard,
    ) -> &mut Self {
        unimplemented!();
    }

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

    /// Add a `having` clause to the query
    pub fn having(&mut self, key: &str, value: Box<dyn Any>) -> &mut Self {
        unimplemented!();
    }

    /// Add a `having` clause to the query, prefixed with an `or`
    pub fn or_having(&mut self, key: &str, value: Box<dyn Any>) -> &mut Self {
        unimplemented!();
    }

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

    /// Specify a condition for the `where` clause of the query
    pub fn r#where(&mut self, key: &str, op: &str, value: Box<dyn Any>) -> &mut Self {
        // @TODO actually implement setting the keys for the where
        self.state.where_values.push(value);

        self
    }

    // Specify a condition for a `where` clause where a column has a value
    pub fn where_eq(&mut self, key: &str, value: Box<dyn Any>) -> &mut Self {
        self.r#where(key, "=", value)
    }

    /// Specify a condition for the `where` clause of the query, prefixed with `or`
    pub fn or_where(&mut self, key: &str, value: Box<dyn Any>) -> &mut Self {
        unimplemented!();
    }

    /// Specify a `where in` clause for the query
    pub fn where_in(&mut self, key: &str, value: Vec<Box<dyn Any>>) -> &mut Self {
        unimplemented!();
    }

    /// Specify a `where in` clause for the query, prefixed with `or`
    pub fn or_where_in(&mut self, key: &str, value: Vec<Box<dyn Any>>) -> &mut Self {
        unimplemented!();
    }

    /// Specify a `where not in` clause for the query
    pub fn where_not_in(&mut self, key: &str, value: Vec<Box<dyn Any>>) -> &mut Self {
        unimplemented!();
    }

    /// Specify a `where not in` clause for the query, prefixed with `or`
    pub fn or_where_not_in(&mut self, key: &str, value: Vec<Box<dyn Any>>) -> &mut Self {
        unimplemented!();
    }

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

    /// Set a key and value for an insert or update query
    pub fn set(&mut self, key: &str, value: Box<dyn Any>) -> &mut Self {
        // @TODO figure a way to make this easier to use
        self.state.set_array_keys.push(key.to_string());
        self.state.values.push(value);

        self
    }

    /// Set a map of data for an insert or update query
    pub fn set_map(&mut self, data: HashMap<String, Box<dyn Any>>) -> &mut Self {
        for (key, value) in data {
            self.set(&key, value);
        }

        self
    }

    /// Convenience method for a `left` join
    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
    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
    pub fn join(
        &mut self,
        table: &str,
        col: &str,
        op: &str,
        value: &str,
        join_type: JoinType,
    ) -> &mut Self {
        let table = self.driver.quote_identifier(table);
        let col = self.driver.quote_identifier(col);
        let condition = table + " ON " + &col + op + value;

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

        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.group_array.push(field.to_string());

        self.state.group_string = " GROUP BY ".to_string() + &self.state.group_array.join(",");

        self
    }

    /// Add an order by clause to the query
    pub fn order_by(&mut self, field: &str, direction: OrderDirection) -> &mut Self {
        if direction == OrderDirection::Rand {
            // @TODO handle random sorting
            unimplemented!();
        }

        let field = self.driver.quote_identifier(field);
        let dir = match direction {
            OrderDirection::Asc => String::from("ASC"),
            OrderDirection::Desc => String::from("DESC"),
            OrderDirection::Rand => String::from("RAND"),
        };
        self.state.order_array.insert(field, dir);

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

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

        let order_str = if direction != OrderDirection::Rand {
            "\nORDER BY ".to_string() + &order_clauses.join(", ")
        } else {
            unimplemented!();
        };

        self.state.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 {
        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 {
        if self.state.query_map.len() == 0 {
            self.state
                .append_query_map(QueryClauseType::GroupStart, " ", "(");
        } else {
            self.state
                .append_query_map(QueryClauseType::GroupStart, " WHERE ", "(");
        }

        self
    }

    /// Start a logical grouping, prefixed with `not`
    pub fn not_group_start(&mut self) -> &mut Self {
        if self.state.query_map.len() == 0 {
            self.state
                .append_query_map(QueryClauseType::GroupStart, " WHERE NOT ", "(");
        } else {
            self.state
                .append_query_map(QueryClauseType::GroupStart, " AND 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 built query
    pub fn get(self) -> Box<dyn Any> {
        unimplemented!();
    }

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

    /// Execute the generated insert query
    pub fn insert(&mut self, table: &str) {
        // @TODO determine query result type
        unimplemented!();
    }

    /// Execute the generated update query
    pub fn update(&mut self, table: &str) {
        // @TODO determine query result type
        unimplemented!();
    }

    /// Execute the generated delete query
    pub fn delete(&mut self, table: &str) {
        unimplemented!();
    }

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

    /// Get the generated SQL for a select query
    pub fn get_compiled_select(self) -> String {
        unimplemented!();
    }

    /// Get the generated SQL for an insert query
    pub fn get_compiled_insert(self) -> String {
        unimplemented!();
    }

    /// Get the generated SQL for an update query
    pub fn get_compiled_update(self) -> String {
        unimplemented!();
    }

    /// Get the generated SQL for a delete query
    pub fn get_compiled_delete(self) -> String {
        unimplemented!();
    }

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

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

        self
    }

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

    fn compile() -> String {
        unimplemented!();
    }
}

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

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

        qb.set("foo", Box::new("bar"));

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

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

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

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

        qb.set_map(authors);

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