use std::io::Cursor;
use std::path::Path;

use anyhow::Context;
use chrono::{DateTime, NaiveDateTime, Utc};
use image::codecs::jpeg::JpegEncoder;
use image::imageops::FilterType;
use image::DynamicImage;
use serde::Deserialize;
use uuid::Uuid;

use crate::models::{Photo, PhotoStatus};
use crate::s3;
use crate::state::AppState;

const PREVIEW_EDGE: u32 = 2048;
const THUMB_EDGE: u32 = 512;

pub const RAW_EXTENSIONS: &[&str] = &[
    "3fr", "arw", "cr2", "cr3", "dng", "erf", "iiq", "kdc", "mef", "mos", "nef", "nrw", "orf",
    "pef", "raf", "raw", "rw2", "rwl", "srw", "x3f",
];

pub fn is_raw_filename(filename: &str) -> bool {
    Path::new(filename)
        .extension()
        .and_then(|e| e.to_str())
        .map(|e| RAW_EXTENSIONS.contains(&e.to_lowercase().as_str()))
        .unwrap_or(false)
}

#[derive(Deserialize)]
struct ProcessPayload {
    photo_id: Uuid,
}

pub async fn process_photo_job(state: &AppState, payload: &serde_json::Value) -> anyhow::Result<()> {
    let payload: ProcessPayload = serde_json::from_value(payload.clone())?;
    process_photo(state, payload.photo_id).await
}

pub async fn process_photo(state: &AppState, photo_id: Uuid) -> anyhow::Result<()> {
    let photo: Option<Photo> = sqlx::query_as("select * from photos where id = $1")
        .bind(photo_id)
        .fetch_optional(&state.db)
        .await?;
    let Some(photo) = photo else {
        tracing::warn!("photo {photo_id} no longer exists, skipping");
        return Ok(());
    };

    sqlx::query("update photos set status = $2, error = null where id = $1")
        .bind(photo_id)
        .bind(PhotoStatus::Processing.as_str())
        .execute(&state.db)
        .await?;

    let dir = tempfile::tempdir().context("creating temp dir")?;
    let extension = Path::new(&photo.filename)
        .extension()
        .and_then(|e| e.to_str())
        .unwrap_or("bin")
        .to_lowercase();
    let src_path = dir.path().join(format!("original.{extension}"));
    let (sha256, crc32) =
        download(state, &s3::original_key(photo_id, &photo.filename), &src_path).await?;
    if photo.sha256.is_none() || photo.crc32.is_none() {
        // Best-effort backfill for pre-hash photos; a duplicate in the same
        // album trips the unique index, which is fine — skip silently.
        if let Err(e) = sqlx::query(
            "update photos set sha256 = coalesce(sha256, $2), crc32 = coalesce(crc32, $3)
             where id = $1",
        )
        .bind(photo_id)
        .bind(&sha256)
        .bind(crc32)
        .execute(&state.db)
        .await
        {
            tracing::debug!("hash backfill skipped for {photo_id}: {e}");
        }
    }

    let meta = exif_metadata(&src_path).await?;

    let render_input = if RAW_EXTENSIONS.contains(&extension.as_str()) {
        extract_embedded_jpeg(&src_path).await?
    } else {
        tokio::fs::read(&src_path).await.context("reading original")?
    };

    let orientation = meta.orientation;
    let (preview, thumb, width, height) =
        tokio::task::spawn_blocking(move || render(&render_input, orientation))
            .await
            .context("render task panicked")??;

    s3::put_bytes(state, &s3::preview_key(photo_id), preview, "image/jpeg").await?;
    s3::put_bytes(state, &s3::thumb_key(photo_id), thumb, "image/jpeg").await?;

    let updated = sqlx::query(
        "update photos
         set status = $5, error = null, width = $2, height = $3,
             taken_at = coalesce($4, taken_at), processed_at = now()
         where id = $1",
    )
    .bind(photo_id)
    .bind(width as i32)
    .bind(height as i32)
    .bind(meta.taken_at)
    .bind(PhotoStatus::Ready.as_str())
    .execute(&state.db)
    .await?;
    if updated.rows_affected() == 0 {
        // Photo was deleted while we were processing; its delete_s3_prefix job
        // may already have run, so remove the derivatives we just re-created.
        tracing::warn!("photo {photo_id} deleted during processing; cleaning up derivatives");
        s3::delete_prefix(state, &s3::photo_prefix(photo_id)).await?;
    }
    Ok(())
}

/// Download the original, hashing along the way so legacy photos (uploaded
/// before hashes existed) can be backfilled.
async fn download(state: &AppState, key: &str, path: &Path) -> anyhow::Result<(String, i64)> {
    use sha2::Digest;
    use tokio::io::{AsyncReadExt, AsyncWriteExt};
    let object = state
        .s3
        .get_object()
        .bucket(&state.config.s3_bucket)
        .key(key)
        .send()
        .await
        .with_context(|| format!("fetching s3://{}/{key}", state.config.s3_bucket))?;
    let mut reader = object.body.into_async_read();
    let mut file = tokio::fs::File::create(path).await?;
    let mut sha = sha2::Sha256::new();
    let mut crc = crc32fast::Hasher::new();
    let mut buf = vec![0u8; 128 * 1024];
    loop {
        let n = reader.read(&mut buf).await?;
        if n == 0 {
            break;
        }
        sha.update(&buf[..n]);
        crc.update(&buf[..n]);
        file.write_all(&buf[..n]).await?;
    }
    file.flush().await?;
    Ok((hex::encode(sha.finalize()), i64::from(crc.finalize())))
}

#[derive(Default)]
struct ExifMeta {
    orientation: u32,
    taken_at: Option<DateTime<Utc>>,
}

async fn exif_metadata(path: &Path) -> anyhow::Result<ExifMeta> {
    let output = tokio::process::Command::new("exiftool")
        .args([
            "-j",
            "-d",
            "%Y-%m-%dT%H:%M:%S",
            "-Orientation#",
            "-DateTimeOriginal",
            "-CreateDate",
            "-OffsetTimeOriginal",
            "-OffsetTime",
        ])
        .arg(path)
        .output()
        .await;
    let output = match output {
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            anyhow::bail!("exiftool is not installed or not on PATH")
        }
        other => other.context("running exiftool")?,
    };
    if !output.status.success() {
        tracing::warn!(
            "exiftool metadata read failed: {}",
            String::from_utf8_lossy(&output.stderr)
        );
        return Ok(ExifMeta::default());
    }
    let parsed: Vec<serde_json::Value> =
        serde_json::from_slice(&output.stdout).context("parsing exiftool json")?;
    let entry = parsed.first().cloned().unwrap_or_default();
    let orientation = entry
        .get("Orientation")
        .and_then(|v| v.as_u64())
        .map(|v| v as u32)
        .unwrap_or(1);
    let offset = ["OffsetTimeOriginal", "OffsetTime"]
        .iter()
        .find_map(|field| entry.get(*field).and_then(|v| v.as_str()));
    let taken_at = ["DateTimeOriginal", "CreateDate"]
        .iter()
        .filter_map(|field| entry.get(*field).and_then(|v| v.as_str()))
        .find_map(|s| parse_exif_datetime(s, offset));
    Ok(ExifMeta {
        orientation,
        taken_at,
    })
}

/// EXIF datetimes are camera-local wall-clock time; apply the EXIF offset tag
/// when the camera recorded one, otherwise fall back to treating it as UTC.
fn parse_exif_datetime(s: &str, offset: Option<&str>) -> Option<DateTime<Utc>> {
    if let Some(offset) = offset {
        if let Ok(dt) = DateTime::parse_from_str(&format!("{s}{offset}"), "%Y-%m-%dT%H:%M:%S%:z") {
            return Some(dt.with_timezone(&Utc));
        }
    }
    NaiveDateTime::parse_from_str(s, "%Y-%m-%dT%H:%M:%S")
        .ok()
        .map(|naive| naive.and_utc())
}

/// Extract the largest embedded JPEG preview from a raw file using exiftool.
async fn extract_embedded_jpeg(path: &Path) -> anyhow::Result<Vec<u8>> {
    let mut best: Vec<u8> = Vec::new();
    for tag in ["-JpgFromRaw", "-PreviewImage", "-OtherImage", "-ThumbnailImage"] {
        let output = tokio::process::Command::new("exiftool")
            .args(["-b", tag])
            .arg(path)
            .output()
            .await
            .context("running exiftool")?;
        if output.status.success() && output.stdout.len() > best.len() {
            best = output.stdout;
        }
        // A full-size embedded preview is comfortably above this; stop early.
        if best.len() > 200_000 {
            break;
        }
    }
    anyhow::ensure!(
        best.len() > 1_000,
        "no usable embedded preview found in raw file"
    );
    Ok(best)
}

fn render(bytes: &[u8], orientation: u32) -> anyhow::Result<(Vec<u8>, Vec<u8>, u32, u32)> {
    let img = image::load_from_memory(bytes).context("decoding image")?;
    let img = apply_orientation(img, orientation);
    let (width, height) = (img.width(), img.height());

    let preview = if width.max(height) > PREVIEW_EDGE {
        img.resize(PREVIEW_EDGE, PREVIEW_EDGE, FilterType::Triangle)
    } else {
        img
    };
    let thumb = preview.resize(THUMB_EDGE, THUMB_EDGE, FilterType::Lanczos3);

    Ok((
        encode_jpeg(&preview, 86)?,
        encode_jpeg(&thumb, 82)?,
        width,
        height,
    ))
}

fn encode_jpeg(img: &DynamicImage, quality: u8) -> anyhow::Result<Vec<u8>> {
    let rgb = img.to_rgb8();
    let mut buf = Cursor::new(Vec::new());
    let encoder = JpegEncoder::new_with_quality(&mut buf, quality);
    rgb.write_with_encoder(encoder).context("encoding jpeg")?;
    Ok(buf.into_inner())
}

fn apply_orientation(img: DynamicImage, orientation: u32) -> DynamicImage {
    match orientation {
        2 => img.fliph(),
        3 => img.rotate180(),
        4 => img.flipv(),
        5 => img.rotate90().fliph(),
        6 => img.rotate90(),
        7 => img.rotate270().fliph(),
        8 => img.rotate270(),
        _ => img,
    }
}