// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! AST types specific to CREATE/ALTER variants of [Statement]
//! (commonly referred to as Data Definition Language, or DDL)
use super::{display_comma_separated, DataType, Expr, Ident, ObjectName};
use std::fmt;

/// An `ALTER TABLE` (`Statement::AlterTable`) operation
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum AlterTableOperation {
    AddColumn(ColumnDef),
    /// `ADD <table_constraint>`
    AddConstraint(TableConstraint),
    DropColumn {
        column: Ident,
        if_exists: bool,
        cascade: bool,
    },
    /// TODO: implement `DROP CONSTRAINT <name>`
    DropConstraint {
        name: Ident,
    },
}

impl fmt::Display for AlterTableOperation {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            AlterTableOperation::AddColumn(column_def) => write!(f, "ADD COLUMN {}", column_def),
            AlterTableOperation::AddConstraint(c) => write!(f, "ADD {}", c),
            AlterTableOperation::DropColumn {
                column,
                if_exists,
                cascade,
            } => write!(
                f,
                "DROP COLUMN {}{} {}",
                if *if_exists { "IF EXISTS " } else { " " },
                column,
                if *cascade { "CASCADE" } else { "" }
            ),
            AlterTableOperation::DropConstraint { name } => write!(f, "DROP CONSTRAINT {}", name),
        }
    }
}

/// A table-level constraint, specified in a `CREATE TABLE` or an
/// `ALTER TABLE ADD <constraint>` statement.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum TableConstraint {
    /// `[ CONSTRAINT <name> ] { PRIMARY KEY | UNIQUE } (<columns>)`
    Unique {
        name: Option<Ident>,
        columns: Vec<Ident>,
        /// Whether this is a `PRIMARY KEY` or just a `UNIQUE` constraint
        is_primary: bool,
    },
    /// A referential integrity constraint (`[ CONSTRAINT <name> ] FOREIGN KEY (<columns>)
    /// REFERENCES <foreign_table> (<referred_columns>)`)
    ForeignKey {
        name: Option<Ident>,
        columns: Vec<Ident>,
        foreign_table: ObjectName,
        referred_columns: Vec<Ident>,
    },
    /// `[ CONSTRAINT <name> ] CHECK (<expr>)`
    Check {
        name: Option<Ident>,
        expr: Box<Expr>,
    },
}

impl fmt::Display for TableConstraint {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            TableConstraint::Unique {
                name,
                columns,
                is_primary,
            } => write!(
                f,
                "{}{} ({})",
                display_constraint_name(name),
                if *is_primary { "PRIMARY KEY" } else { "UNIQUE" },
                display_comma_separated(columns)
            ),
            TableConstraint::ForeignKey {
                name,
                columns,
                foreign_table,
                referred_columns,
            } => write!(
                f,
                "{}FOREIGN KEY ({}) REFERENCES {}({})",
                display_constraint_name(name),
                display_comma_separated(columns),
                foreign_table,
                display_comma_separated(referred_columns)
            ),
            TableConstraint::Check { name, expr } => {
                write!(f, "{}CHECK ({})", display_constraint_name(name), expr)
            }
        }
    }
}

/// SQL column definition
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ColumnDef {
    pub name: Ident,
    pub data_type: DataType,
    pub collation: Option<ObjectName>,
    pub options: Vec<ColumnOptionDef>,
}

impl fmt::Display for ColumnDef {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{} {}", self.name, self.data_type)?;
        for option in &self.options {
            write!(f, " {}", option)?;
        }
        Ok(())
    }
}

/// An optionally-named `ColumnOption`: `[ CONSTRAINT <name> ] <column-option>`.
///
/// Note that implementations are substantially more permissive than the ANSI
/// specification on what order column options can be presented in, and whether
/// they are allowed to be named. The specification distinguishes between
/// constraints (NOT NULL, UNIQUE, PRIMARY KEY, and CHECK), which can be named
/// and can appear in any order, and other options (DEFAULT, GENERATED), which
/// cannot be named and must appear in a fixed order. PostgreSQL, however,
/// allows preceding any option with `CONSTRAINT <name>`, even those that are
/// not really constraints, like NULL and DEFAULT. MSSQL is less permissive,
/// allowing DEFAULT, UNIQUE, PRIMARY KEY and CHECK to be named, but not NULL or
/// NOT NULL constraints (the last of which is in violation of the spec).
///
/// For maximum flexibility, we don't distinguish between constraint and
/// non-constraint options, lumping them all together under the umbrella of
/// "column options," and we allow any column option to be named.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ColumnOptionDef {
    pub name: Option<Ident>,
    pub option: ColumnOption,
}

impl fmt::Display for ColumnOptionDef {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}{}", display_constraint_name(&self.name), self.option)
    }
}

/// `ColumnOption`s are modifiers that follow a column definition in a `CREATE
/// TABLE` statement.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ColumnOption {
    /// `NULL`
    Null,
    /// `NOT NULL`
    NotNull,
    /// `DEFAULT <restricted-expr>`
    Default(Expr),
    /// `{ PRIMARY KEY | UNIQUE }`
    Unique {
        is_primary: bool,
    },
    /// A referential integrity constraint (`[FOREIGN KEY REFERENCES
    /// <foreign_table> (<referred_columns>)`).
    ForeignKey {
        foreign_table: ObjectName,
        referred_columns: Vec<Ident>,
    },
    // `CHECK (<expr>)`
    Check(Expr),
}

impl fmt::Display for ColumnOption {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use ColumnOption::*;
        match self {
            Null => write!(f, "NULL"),
            NotNull => write!(f, "NOT NULL"),
            Default(expr) => write!(f, "DEFAULT {}", expr),
            Unique { is_primary } => {
                write!(f, "{}", if *is_primary { "PRIMARY KEY" } else { "UNIQUE" })
            }
            ForeignKey {
                foreign_table,
                referred_columns,
            } => write!(
                f,
                "REFERENCES {} ({})",
                foreign_table,
                display_comma_separated(referred_columns)
            ),
            Check(expr) => write!(f, "CHECK ({})", expr),
        }
    }
}

fn display_constraint_name<'a>(name: &'a Option<Ident>) -> impl fmt::Display + 'a {
    struct ConstraintName<'a>(&'a Option<Ident>);
    impl<'a> fmt::Display for ConstraintName<'a> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            if let Some(name) = self.0 {
                write!(f, "CONSTRAINT {} ", name)?;
            }
            Ok(())
        }
    }
    ConstraintName(name)
}