//! Traits dealing with SQLite data types.
//!
//! SQLite uses a [dynamic type system](https://www.sqlite.org/datatype3.html). Implementations of
//! the `ToSql` and `FromSql` traits are provided for the basic types that SQLite provides methods
//! for:
//!
//! * C integers and doubles (`c_int` and `c_double`)
//! * Strings (`String` and `&str`)
//! * Blobs (`Vec<u8>` and `&[u8]`)
//!
//! Additionally, because it is such a common data type, implementations are provided for
//! `time::Timespec` that use a string for storage (using the same format string,
//! `"%Y-%m-%d %H:%M:%S"`, as SQLite's builtin
//! [datetime](https://www.sqlite.org/lang_datefunc.html) function.  Note that this storage
//! truncates timespecs to the nearest second. If you want different storage for timespecs, you can
//! use a newtype. For example, to store timespecs as doubles:
//!
//! `ToSql` and `FromSql` are also implemented for `Option<T>` where `T` implements `ToSql` or
//! `FromSql` for the cases where you want to know if a value was NULL (which gets translated to
//! `None`). If you get a value that was NULL in SQLite but you store it into a non-`Option` value
//! in Rust, you will get a "sensible" zero value - 0 for numeric types (including timespecs), an
//! empty string, or an empty vector of bytes.
//!
//! ```rust,ignore
//! extern crate rusqlite;
//! extern crate libc;
//!
//! use rusqlite::types::{FromSql, ToSql};
//! use rusqlite::{ffi, SqliteResult};
//! use libc::c_int;
//! use time;
//!
//! pub struct TimespecSql(pub time::Timespec);
//!
//! impl FromSql for TimespecSql {
//!     unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int)
//!             -> SqliteResult<TimespecSql> {
//!         let as_f64_result = FromSql::column_result(stmt, col);
//!         as_f64_result.map(|as_f64: f64| {
//!             TimespecSql(time::Timespec{ sec: as_f64.trunc() as i64,
//!                                         nsec: (as_f64.fract() * 1.0e9) as i32 })
//!         })
//!     }
//! }
//!
//! impl ToSql for TimespecSql {
//!     unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
//!         let TimespecSql(ts) = *self;
//!         let as_f64 = ts.sec as f64 + (ts.nsec as f64) / 1.0e9;
//!         as_f64.bind_parameter(stmt, col)
//!     }
//! }
//! ```

extern crate time;

use libc::{c_int, c_double};
use std::c_str::{CString};
use std::mem;
use super::ffi;
use super::{SqliteResult, SqliteError};

const SQLITE_DATETIME_FMT: &'static str = "%Y-%m-%d %H:%M:%S";

/// A trait for types that can be converted into SQLite values.
pub trait ToSql {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int;
}

/// A trait for types that can be created from a SQLite value.
pub trait FromSql {
    unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int) -> SqliteResult<Self>;
}

macro_rules! raw_to_impl(
    ($t:ty, $f:ident) => (
        impl ToSql for $t {
            unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
                ffi::$f(stmt, col, *self)
            }
        }
    )
);

raw_to_impl!(c_int, sqlite3_bind_int);
raw_to_impl!(i64, sqlite3_bind_int64);
raw_to_impl!(c_double, sqlite3_bind_double);

impl<'a> ToSql for &'a str {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        self.with_c_str(|c_str| {
            ffi::sqlite3_bind_text(stmt, col, c_str, -1, Some(ffi::SQLITE_TRANSIENT()))
        })
    }
}

impl ToSql for String {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        self.as_slice().bind_parameter(stmt, col)
    }
}

impl<'a> ToSql for &'a [u8] {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        ffi::sqlite3_bind_blob(
            stmt, col, mem::transmute(self.as_ptr()), self.len() as c_int,
            Some(ffi::SQLITE_TRANSIENT()))
    }
}

impl ToSql for Vec<u8> {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        self.as_slice().bind_parameter(stmt, col)
    }
}

impl ToSql for time::Timespec {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        let time_str = time::at_utc(*self).strftime(SQLITE_DATETIME_FMT).unwrap().to_string();
        time_str.bind_parameter(stmt, col)
    }
}

impl<T: ToSql> ToSql for Option<T> {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        match *self {
            None => ffi::sqlite3_bind_null(stmt, col),
            Some(ref t) => t.bind_parameter(stmt, col),
        }
    }
}

/// Empty struct that can be used to fill in a query parameter as `NULL`.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{SqliteConnection, SqliteResult};
/// # use rusqlite::types::{Null};
/// fn insert_null(conn: &SqliteConnection) -> SqliteResult<uint> {
///     conn.execute("INSERT INTO people (name) VALUES (?)", &[&Null])
/// }
/// ```
#[deriving(Copy)]
pub struct Null;

impl ToSql for Null {
    unsafe fn bind_parameter(&self, stmt: *mut ffi::sqlite3_stmt, col: c_int) -> c_int {
        ffi::sqlite3_bind_null(stmt, col)
    }
}

macro_rules! raw_from_impl(
    ($t:ty, $f:ident) => (
        impl FromSql for $t {
            unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int) -> SqliteResult<$t> {
                Ok(ffi::$f(stmt, col))
            }
        }
    )
);

raw_from_impl!(c_int, sqlite3_column_int);
raw_from_impl!(i64, sqlite3_column_int64);
raw_from_impl!(c_double, sqlite3_column_double);

impl FromSql for String {
    unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int) -> SqliteResult<String> {
        let c_text = ffi::sqlite3_column_text(stmt, col);
        if c_text.is_null() {
            Ok("".to_string())
        } else {
            match CString::new(mem::transmute(c_text), false).as_str() {
                Some(s) => Ok(s.to_string()),
                None => Err(SqliteError{ code: ffi::SQLITE_MISMATCH,
                    message: "Could not convert text to UTF-8".to_string() })
            }
        }
    }
}

impl FromSql for Vec<u8> {
    unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int) -> SqliteResult<Vec<u8>> {
        let c_blob = ffi::sqlite3_column_blob(stmt, col);
        let len = ffi::sqlite3_column_bytes(stmt, col);

        assert!(len >= 0); let len = len as uint;

        Ok(Vec::from_raw_buf(mem::transmute(c_blob), len))
    }
}

impl FromSql for time::Timespec {
    unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt,
                            col: c_int) -> SqliteResult<time::Timespec> {
        let col_str = FromSql::column_result(stmt, col);
        col_str.and_then(|txt: String| {
            time::strptime(txt.as_slice(), SQLITE_DATETIME_FMT).map(|tm| {
                tm.to_timespec()
            }).map_err(|parse_error| {
                SqliteError{ code: ffi::SQLITE_MISMATCH, message: format!("{}", parse_error) }
            })
        })
    }
}

impl<T: FromSql> FromSql for Option<T> {
    unsafe fn column_result(stmt: *mut ffi::sqlite3_stmt, col: c_int) -> SqliteResult<Option<T>> {
        if ffi::sqlite3_column_type(stmt, col) == ffi::SQLITE_NULL {
            Ok(None)
        } else {
            FromSql::column_result(stmt, col).map(|t| Some(t))
        }
    }
}

#[cfg(test)]
mod test {
    use SqliteConnection;
    use super::time;

    fn checked_memory_handle() -> SqliteConnection {
        let db = SqliteConnection::open(":memory:").unwrap();
        db.execute_batch("CREATE TABLE foo (b BLOB, t TEXT)").unwrap();
        db
    }

    #[test]
    fn test_blob() {
        let db = checked_memory_handle();

        let v1234 = vec![1u8,2,3,4];
        db.execute("INSERT INTO foo(b) VALUES (?)", &[&v1234]).unwrap();

        let v: Vec<u8> = db.query_row("SELECT b FROM foo", &[], |r| r.get(0));
        assert_eq!(v, v1234);
    }

    #[test]
    fn test_str() {
        let db = checked_memory_handle();

        let s = "hello, world!";
        db.execute("INSERT INTO foo(t) VALUES (?)", &[&s.to_string()]).unwrap();

        let from: String = db.query_row("SELECT t FROM foo", &[], |r| r.get(0));
        assert_eq!(from.as_slice(), s);
    }

    #[test]
    fn test_timespec() {
        let db = checked_memory_handle();

        let ts = time::Timespec{sec: 10_000, nsec: 0 };
        db.execute("INSERT INTO foo(t) VALUES (?)", &[&ts]).unwrap();

        let from: time::Timespec = db.query_row("SELECT t FROM foo", &[], |r| r.get(0));
        assert_eq!(from, ts);
    }

    #[test]
    fn test_option() {
        let db = checked_memory_handle();

        let s = Some("hello, world!");
        let b = Some(vec![1u8,2,3,4]);

        db.execute("INSERT INTO foo(t) VALUES (?)", &[&s]).unwrap();
        db.execute("INSERT INTO foo(b) VALUES (?)", &[&b]).unwrap();

        let mut stmt = db.prepare("SELECT t, b FROM foo ORDER BY ROWID ASC").unwrap();
        let mut rows = stmt.query(&[]).unwrap();

        let row1 = rows.next().unwrap().unwrap();
        let s1: Option<String> = row1.get(0);
        let b1: Option<Vec<u8>> = row1.get(1);
        assert_eq!(s.unwrap(), s1.unwrap().as_slice());
        assert!(b1.is_none());

        let row2 = rows.next().unwrap().unwrap();
        let s2: Option<String> = row2.get(0);
        let b2: Option<Vec<u8>> = row2.get(1);
        assert!(s2.is_none());
        assert_eq!(b, b2);
    }
}