use ffi;
use libc::{c_char, c_int, c_void};
use std::marker::PhantomData;
use std::path::Path;

use {Result, Statement};

/// A connection to a database.
pub struct Connection {
    raw: *mut ffi::sqlite3,
    busy_callback: Option<Box<FnMut(usize) -> bool>>,
    phantom: PhantomData<ffi::sqlite3>,
}

impl Connection {
    /// Open a connection to a new or existing database.
    pub fn open<T: AsRef<Path>>(path: T) -> Result<Connection> {
        let mut raw = 0 as *mut _;
        unsafe {
            ok!(ffi::sqlite3_open_v2(path_to_cstr!(path.as_ref()).as_ptr(), &mut raw,
                                     ffi::SQLITE_OPEN_CREATE | ffi::SQLITE_OPEN_READWRITE,
                                     0 as *const _));
        }
        Ok(Connection { raw: raw, busy_callback: None, phantom: PhantomData })
    }

    /// Execute a query without processing the resulting rows if any.
    #[inline]
    pub fn execute<T: AsRef<str>>(&self, query: T) -> Result<()> {
        unsafe {
            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_cstr!(query.as_ref()).as_ptr(), None,
                                            0 as *mut _, 0 as *mut _));
        }
        Ok(())
    }

    /// Execute a query and process the resulting rows if any.
    ///
    /// The callback is triggered for each row. If the callback returns `false`,
    /// no more rows will be processed. For large queries and non-string data
    /// types, prepared statement are highly preferable; see `prepare`.
    #[inline]
    pub fn process<T: AsRef<str>, F>(&self, query: T, callback: F) -> Result<()>
        where F: FnMut(&[(&str, Option<&str>)]) -> bool
    {
        unsafe {
            let callback = Box::new(callback);
            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_cstr!(query.as_ref()).as_ptr(),
                                            Some(process_callback::<F>),
                                            &*callback as *const F as *mut F as *mut _,
                                            0 as *mut _));
        }
        Ok(())
    }

    /// Create a prepared statement.
    #[inline]
    pub fn prepare<'l, T: AsRef<str>>(&'l self, query: T) -> Result<Statement<'l>> {
        ::statement::new(self.raw, query)
    }

    /// Set a callback for handling busy events.
    ///
    /// The callback is triggered when the database cannot perform an operation
    /// due to processing of some other request. If the callback returns `true`,
    /// the operation will be repeated.
    pub fn set_busy_handler<F>(&mut self, callback: F) -> Result<()>
        where F: FnMut(usize) -> bool + 'static
    {
        try!(self.remove_busy_handler());
        unsafe {
            let callback = Box::new(callback);
            let result = ffi::sqlite3_busy_handler(self.raw, Some(busy_callback::<F>),
                                                   &*callback as *const F as *mut F as *mut _);
            self.busy_callback = Some(callback);
            ok!(self.raw, result);
        }
        Ok(())
    }

    /// Set an implicit callback for handling busy events that tries to repeat
    /// rejected operations until a timeout expires.
    #[inline]
    pub fn set_busy_timeout(&mut self, milliseconds: usize) -> Result<()> {
        unsafe { ok!(self.raw, ffi::sqlite3_busy_timeout(self.raw, milliseconds as c_int)) };
        Ok(())
    }

    /// Remove the callback handling busy events.
    #[inline]
    pub fn remove_busy_handler(&mut self) -> Result<()> {
        self.busy_callback = None;
        unsafe { ok!(self.raw, ffi::sqlite3_busy_handler(self.raw, None, 0 as *mut _)) };
        Ok(())
    }
}

impl Drop for Connection {
    #[cfg(not(feature = "sqlite3-close-v2"))]
    #[inline]
    #[allow(unused_must_use)]
    fn drop(&mut self) {
        self.remove_busy_handler();
        unsafe { ffi::sqlite3_close(self.raw) };
    }

    #[cfg(feature = "sqlite3-close-v2")]
    #[inline]
    #[allow(unused_must_use)]
    fn drop(&mut self) {
        self.remove_busy_handler();
        unsafe { ffi::sqlite3_close_v2(self.raw) };
    }
}

extern fn busy_callback<F>(callback: *mut c_void, attempts: c_int) -> c_int
    where F: FnMut(usize) -> bool
{
    unsafe { if (*(callback as *mut F))(attempts as usize) { 1 } else { 0 } }
}

extern fn process_callback<F>(callback: *mut c_void, count: c_int, values: *mut *mut c_char,
                              columns: *mut *mut c_char) -> c_int
    where F: FnMut(&[(&str, Option<&str>)]) -> bool
{
    unsafe {
        let mut pairs = Vec::with_capacity(count as usize);

        for i in 0..(count as isize) {
            let column = {
                let pointer = *columns.offset(i);
                debug_assert!(!pointer.is_null());
                c_str_to_str!(pointer).unwrap()
            };
            let value = {
                let pointer = *values.offset(i);
                if pointer.is_null() {
                    None
                } else {
                    Some(c_str_to_str!(pointer).unwrap())
                }
            };
            pairs.push((column, value));
        }

        if (*(callback as *mut F))(&pairs) { 0 } else { 1 }
    }
}