//! Thin safe wrapper over the `cam_wrapper` C component (see
//! `components/cam_wrapper`).
//!
//! The pin map matches the XIAO ESP32S3 Sense camera connector, which is the
//! common OV2640/OV3660 wiring on an ESP32-S3-N16R8. Adjust `PINS` at the
//! bottom of this file if your board wires the DVP bus differently.

use std::ffi::CStr;

use anyhow::{anyhow, Result};
use esp_idf_svc::sys;
// bindgen names C enum variants `<enum type>_<VARIANT>`, so alias them to
// something readable here instead of scattering those prefixes around.
use esp_idf_svc::sys::camera::{
    cam_wrapper_fb_location_t_CAM_WRAPPER_FB_IN_PSRAM as FB_IN_PSRAM,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_CIF as FRAMESIZE_CIF,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_HVGA as FRAMESIZE_HVGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_QQVGA as FRAMESIZE_QQVGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_QVGA as FRAMESIZE_QVGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_SVGA as FRAMESIZE_SVGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_SXGA as FRAMESIZE_SXGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_UXGA as FRAMESIZE_UXGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_VGA as FRAMESIZE_VGA,
    cam_wrapper_framesize_t_CAM_WRAPPER_FRAMESIZE_XGA as FRAMESIZE_XGA,
    cam_wrapper_grab_mode_t_CAM_WRAPPER_GRAB_LATEST as GRAB_LATEST,
    cam_wrapper_pixel_format_t_CAM_WRAPPER_PIXFORMAT_JPEG as PIXFORMAT_JPEG,
    cam_wrapper_sensor_t_CAM_WRAPPER_SENSOR_AUTO as SENSOR_AUTO,
    cam_wrapper_sensor_t_CAM_WRAPPER_SENSOR_OV2640 as SENSOR_OV2640,
    cam_wrapper_sensor_t_CAM_WRAPPER_SENSOR_OV3660 as SENSOR_OV3660,
    cam_wrapper_sensor_t_CAM_WRAPPER_SENSOR_OV5640 as SENSOR_OV5640,
};

/// Capture resolution.
///
/// Anything above CIF needs PSRAM, which the N16R8 has; the bandwidth cost of
/// the bigger sizes is real, so start at VGA and only go higher if the link
/// keeps up.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Resolution {
    Qqvga,
    Qvga,
    Cif,
    Hvga,
    Vga,
    Svga,
    Xga,
    Sxga,
    Uxga,
}

impl Resolution {
    fn framesize(self) -> sys::camera::cam_wrapper_framesize_t {
        match self {
            Resolution::Qqvga => FRAMESIZE_QQVGA,
            Resolution::Qvga => FRAMESIZE_QVGA,
            Resolution::Cif => FRAMESIZE_CIF,
            Resolution::Hvga => FRAMESIZE_HVGA,
            Resolution::Vga => FRAMESIZE_VGA,
            Resolution::Svga => FRAMESIZE_SVGA,
            Resolution::Xga => FRAMESIZE_XGA,
            Resolution::Sxga => FRAMESIZE_SXGA,
            Resolution::Uxga => FRAMESIZE_UXGA,
        }
    }
}

impl std::str::FromStr for Resolution {
    type Err = anyhow::Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_ascii_lowercase().as_str() {
            "qqvga" => Ok(Resolution::Qqvga),
            "qvga" => Ok(Resolution::Qvga),
            "cif" => Ok(Resolution::Cif),
            "hvga" => Ok(Resolution::Hvga),
            "vga" => Ok(Resolution::Vga),
            "svga" => Ok(Resolution::Svga),
            "xga" => Ok(Resolution::Xga),
            "sxga" => Ok(Resolution::Sxga),
            "uxga" => Ok(Resolution::Uxga),
            other => Err(anyhow!("unknown resolution {other:?}")),
        }
    }
}
use log::info;

/// Sensor override. `Auto` lets esp32-camera probe the SCCB bus, which is what
/// you want unless the probe is ambiguous.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum SensorHint {
    Auto,
    Ov2640,
    Ov3660,
    Ov5640,
}

impl From<SensorHint> for sys::camera::cam_wrapper_sensor_t {
    fn from(hint: SensorHint) -> Self {
        match hint {
            SensorHint::Auto => SENSOR_AUTO,
            SensorHint::Ov2640 => SENSOR_OV2640,
            SensorHint::Ov3660 => SENSOR_OV3660,
            SensorHint::Ov5640 => SENSOR_OV5640,
        }
    }
}

/// One captured JPEG frame. Holds the driver frame buffer, so the data is only
/// valid until the `Frame` is dropped.
pub struct Frame {
    fb: sys::camera::cam_wrapper_fb_t,
}

impl Frame {
    pub fn data(&self) -> &[u8] {
        if self.fb.data.is_null() || self.fb.len == 0 {
            return &[];
        }

        // SAFETY: `data` points at `len` bytes owned by esp32-camera, which
        // stays valid until this Frame is dropped (cam_wrapper_fb_release).
        unsafe { std::slice::from_raw_parts(self.fb.data, self.fb.len) }
    }

    /// Size of the JPEG in bytes.
    ///
    /// Reported in the sender's statistics, which is how a frame rate problem gets
    /// attributed to the capture side or the transport side.
    #[allow(dead_code)]
    pub fn len(&self) -> usize {
        self.fb.len
    }

    /// Capture width in pixels, as the sensor actually produced it (which can be
    /// smaller than the requested frame size).
    pub fn width(&self) -> usize {
        self.fb.width
    }

    /// Capture height in pixels.
    pub fn height(&self) -> usize {
        self.fb.height
    }
}

impl Drop for Frame {
    fn drop(&mut self) {
        unsafe { sys::camera::cam_wrapper_fb_release(&mut self.fb) }
    }
}

/// The driver could not hand out a frame.
#[derive(Debug, Clone, Copy)]
pub struct FrameError;

impl std::fmt::Display for FrameError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str("camera returned no frame")
    }
}

impl std::error::Error for FrameError {}

/// An initialized camera.
///
/// Held for the lifetime of the program: esp32-camera keeps a task and the
/// frame buffers running, and tearing them down would only be needed to power
/// the sensor down, which this program never does.
pub struct Camera {
    sensor: SensorHint,
}

impl Camera {
    /// Brings up the sensor and blocks until it has produced frames.
    ///
    /// `vsync_invert` should be true for a directly connected DVP VSYNC (the
    /// esp32-camera default) and false if the board inverts the line in hardware.
    pub fn init(
        sensor: SensorHint,
        resolution: Resolution,
        jpeg_quality: u8,
        vsync_invert: bool,
    ) -> Result<Self> {
        if jpeg_quality > 63 {
            return Err(anyhow!("jpeg_quality must be 0-63, got {jpeg_quality}"));
        }

        let config = sys::camera::cam_wrapper_config_t {
            pin_pwdn: -1,
            pin_reset: pins::RESET,
            pin_xclk: pins::XCLK,
            pin_sccb_sda: pins::SIOD,
            pin_sccb_scl: pins::SIOC,
            pin_d: pins::DATA,
            pin_vsync: pins::VSYNC,
            pin_href: pins::HREF,
            pin_pclk: pins::PCLK,

            // 20 MHz is what the OV5640 datasheet calls for, and esp32-camera's
            // OV5640 driver is only PLL-tuned for it; raising this without
            // retuning the sensor's own PLL just corrupts frames.
            xclk_freq_hz: 20_000_000,
            ledc_timer: 0,
            ledc_channel: 0,

            pixel_format: PIXFORMAT_JPEG,
            frame_size: resolution.framesize(),
            jpeg_quality: jpeg_quality as i32,
            // Three buffers, not two: esp32-camera needs a free buffer at every
            // VSYNC, and with two a client that is still draining the previous
            // frame costs a whole capture period. One is spent filling, one is
            // being written to the socket, and one is spare for the moment the
            // write blocks.
            fb_count: 3,
            fb_location: FB_IN_PSRAM,
            // LATEST keeps the newest frame in the queue instead of handing out
            // whatever was captured first, which matters once a client is slow
            // enough for frames to pile up.
            grab_mode: GRAB_LATEST,
            sccb_i2c_port: 0,

            // esp32-camera inverts VSYNC by default, which is right for the
            // large majority of DVP sensors. A board that inverts the line
            // itself needs this cleared: a mismatch here does not fail, it
            // makes the driver latch frames on the wrong edge and the frame rate
            // collapses while the pictures still look plausible.
            vsync_invert: if vsync_invert { 1 } else { 0 },
        };

        let rc = unsafe { sys::camera::cam_wrapper_init(&config, sensor.into()) };

        if rc != 0 {
            return Err(anyhow!(
                "camera init failed (esp_err 0x{:x}) - check the DVP/SCCB wiring and that \
                 octal PSRAM is enabled",
                rc
            ));
        }

        info!("camera ready: {}", Self::sensor_name());

        Ok(Self { sensor })
    }

    pub fn sensor_name() -> String {
        unsafe {
            let ptr = sys::camera::cam_wrapper_sensor_name();

            if ptr.is_null() {
                String::from("unknown")
            } else {
                CStr::from_ptr(ptr).to_string_lossy().into_owned()
            }
        }
    }

    /// Grabs the next frame.
    ///
    /// This blocks until the sensor has one, which is what paces the stream.
    /// `Err` means the driver could not hand out a frame at all; the camera is
    /// still usable afterwards, so callers should keep going rather than treat
    /// it as fatal.
    pub fn next_frame(&self) -> Result<Frame, FrameError> {
        let mut fb: sys::camera::cam_wrapper_fb_t = unsafe { std::mem::zeroed() };

        let rc = unsafe { sys::camera::cam_wrapper_fb_get(&mut fb, self.sensor.into()) };

        if rc != 0 || fb.data.is_null() || fb.len == 0 {
            // Nothing was handed out, but be defensive in case a future
            // driver version sets a partial frame.
            unsafe { sys::camera::cam_wrapper_fb_release(&mut fb) };
            return Err(FrameError);
        }

        Ok(Frame { fb })
    }
}

/// Camera connector of the Freenove ESP32-S3-WROOM CAM board.
///
/// Every pin here is one the ESP32-S3 leaves free: 26..37 are bonded to the
/// module's SPI flash and octal PSRAM, 19/20 are the native USB pair this
/// firmware logs over, and 43/44 are the console UART. Touching IO_MUX on any
/// of the flash/PSRAM pins hangs the CPU mid-transfer, which is what happens if
/// you reuse a pin map written for a different board.
///
/// The data bus is the sensor's Y2..Y9, i.e. the low byte of the 10-bit pixel
/// word, so Y2 is D0 and Y9 is D7.
mod pins {
    pub const RESET: i32 = 0;
    pub const XCLK: i32 = 15;
    pub const PCLK: i32 = 13;
    pub const VSYNC: i32 = 6;
    pub const HREF: i32 = 7;
    pub const SIOD: i32 = 4;
    pub const SIOC: i32 = 5;

    /// D0..D7 == Y2..Y9, in the order `camera_config_t` expects.
    pub const DATA: [i32; 8] = [11, 9, 8, 10, 12, 18, 17, 16];
}