//! Tracing and profiling functions. Error and warning log.

use std::ffi::{CStr, CString};
use std::mem;
use std::os::raw::{c_char, c_int, c_void};
use std::panic::catch_unwind;
use std::ptr;
use std::time::Duration;

use super::ffi;
use crate::error::error_from_sqlite_code;
use crate::{Connection, Result};

/// Set up the process-wide SQLite error logging callback.
/// This function is marked unsafe for two reasons:
///
/// * The function is not threadsafe. No other SQLite calls may be made while
///   `config_log` is running, and multiple threads may not call `config_log`
///   simultaneously.
/// * The provided `callback` itself function has two requirements:
///     * It must not invoke any SQLite calls.
///     * It must be threadsafe if SQLite is used in a multithreaded way.
///
/// cf [The Error And Warning Log](http://sqlite.org/errlog.html).
pub unsafe fn config_log(callback: Option<fn(c_int, &str)>) -> Result<()> {
    extern "C" fn log_callback(p_arg: *mut c_void, err: c_int, msg: *const c_char) {
        let c_slice = unsafe { CStr::from_ptr(msg).to_bytes() };
        let callback: fn(c_int, &str) = unsafe { mem::transmute(p_arg) };

        let s = String::from_utf8_lossy(c_slice);
        let _ = catch_unwind(|| callback(err, &s));
    }

    let rc = match callback {
        Some(f) => {
            let p_arg: *mut c_void = mem::transmute(f);
            ffi::sqlite3_config(
                ffi::SQLITE_CONFIG_LOG,
                log_callback as extern "C" fn(_, _, _),
                p_arg,
            )
        }
        None => {
            let nullptr: *mut c_void = ptr::null_mut();
            ffi::sqlite3_config(ffi::SQLITE_CONFIG_LOG, nullptr, nullptr)
        }
    };

    if rc == ffi::SQLITE_OK {
        Ok(())
    } else {
        Err(error_from_sqlite_code(rc, None))
    }
}

/// Write a message into the error log established by `config_log`.
pub fn log(err_code: c_int, msg: &str) {
    let msg = CString::new(msg).expect("SQLite log messages cannot contain embedded zeroes");
    unsafe {
        ffi::sqlite3_log(err_code, msg.as_ptr());
    }
}

impl Connection {
    /// Register or clear a callback function that can be used for tracing the
    /// execution of SQL statements.
    ///
    /// Prepared statement placeholders are replaced/logged with their assigned
    /// values. There can only be a single tracer defined for each database
    /// connection. Setting a new tracer clears the old one.
    pub fn trace(&mut self, trace_fn: Option<fn(&str)>) {
        unsafe extern "C" fn trace_callback(p_arg: *mut c_void, z_sql: *const c_char) {
            let trace_fn: fn(&str) = mem::transmute(p_arg);
            let c_slice = CStr::from_ptr(z_sql).to_bytes();
            let s = String::from_utf8_lossy(c_slice);
            let _ = catch_unwind(|| trace_fn(&s));
        }

        let c = self.db.borrow_mut();
        match trace_fn {
            Some(f) => unsafe {
                ffi::sqlite3_trace(c.db(), Some(trace_callback), mem::transmute(f));
            },
            None => unsafe {
                ffi::sqlite3_trace(c.db(), None, ptr::null_mut());
            },
        }
    }

    /// Register or clear a callback function that can be used for profiling
    /// the execution of SQL statements.
    ///
    /// There can only be a single profiler defined for each database
    /// connection. Setting a new profiler clears the old one.
    pub fn profile(&mut self, profile_fn: Option<fn(&str, Duration)>) {
        unsafe extern "C" fn profile_callback(
            p_arg: *mut c_void,
            z_sql: *const c_char,
            nanoseconds: u64,
        ) {
            let profile_fn: fn(&str, Duration) = mem::transmute(p_arg);
            let c_slice = CStr::from_ptr(z_sql).to_bytes();
            let s = String::from_utf8_lossy(c_slice);
            const NANOS_PER_SEC: u64 = 1_000_000_000;

            let duration = Duration::new(
                nanoseconds / NANOS_PER_SEC,
                (nanoseconds % NANOS_PER_SEC) as u32,
            );
            let _ = catch_unwind(|| profile_fn(&s, duration));
        }

        let c = self.db.borrow_mut();
        match profile_fn {
            Some(f) => unsafe {
                ffi::sqlite3_profile(c.db(), Some(profile_callback), mem::transmute(f))
            },
            None => unsafe { ffi::sqlite3_profile(c.db(), None, ptr::null_mut()) },
        };
    }
}

#[cfg(test)]
mod test {
    use std::sync::Mutex;
    use std::time::Duration;
    use lazy_static::lazy_static;

    use crate::Connection;

    #[test]
    fn test_trace() {
        lazy_static! {
            static ref TRACED_STMTS: Mutex<Vec<String>> = Mutex::new(Vec::new());
        }
        fn tracer(s: &str) {
            let mut traced_stmts = TRACED_STMTS.lock().unwrap();
            traced_stmts.push(s.to_owned());
        }

        let mut db = Connection::open_in_memory().unwrap();
        db.trace(Some(tracer));
        {
            let _ = db.query_row("SELECT ?", &[1i32], |_| Ok(()));
            let _ = db.query_row("SELECT ?", &["hello"], |_| Ok(()));
        }
        db.trace(None);
        {
            let _ = db.query_row("SELECT ?", &[2i32], |_| Ok(()));
            let _ = db.query_row("SELECT ?", &["goodbye"], |_| Ok(()));
        }

        let traced_stmts = TRACED_STMTS.lock().unwrap();
        assert_eq!(traced_stmts.len(), 2);
        assert_eq!(traced_stmts[0], "SELECT 1");
        assert_eq!(traced_stmts[1], "SELECT 'hello'");
    }

    #[test]
    fn test_profile() {
        lazy_static! {
            static ref PROFILED: Mutex<Vec<(String, Duration)>> = Mutex::new(Vec::new());
        }
        fn profiler(s: &str, d: Duration) {
            let mut profiled = PROFILED.lock().unwrap();
            profiled.push((s.to_owned(), d));
        }

        let mut db = Connection::open_in_memory().unwrap();
        db.profile(Some(profiler));
        db.execute_batch("PRAGMA application_id = 1").unwrap();
        db.profile(None);
        db.execute_batch("PRAGMA application_id = 2").unwrap();

        let profiled = PROFILED.lock().unwrap();
        assert_eq!(profiled.len(), 1);
        assert_eq!(profiled[0].0, "PRAGMA application_id = 1");
    }
}