//! 剪贴板监听线程：基于 GetClipboardSequenceNumber 轮询
//!
//! 选用轮询而非 AddClipboardFormatListener 消息窗口：实现更简单、无需消息循环，
//! 250ms 间隔兼顾响应速度与开销，且 GetClipboardSequenceNumber 不需要 OpenClipboard，开销极小。

use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

use tauri::{AppHandle, Emitter};

use super::reader::{read_clipboard, ClipData};
use super::storage::{NewItem, Storage};
use windows_sys::Win32::System::DataExchange::GetClipboardSequenceNumber;

/// 启动监听线程，返回 JoinHandle。
/// `suppress` 记录本应用 copy_back 写入后的剪贴板序列号，用于跳过自身写入产生的记录。
pub fn start_monitor(
    storage: Arc<Storage>,
    app: AppHandle,
    settings: Arc<Mutex<super::manager::ClipboardSettings>>,
    suppress: Arc<Mutex<Option<u32>>>,
    stop: Arc<AtomicBool>,
) -> thread::JoinHandle<()> {
    thread::spawn(move || loop {
        if stop.load(Ordering::SeqCst) {
            break;
        }
        thread::sleep(Duration::from_millis(250));
        if stop.load(Ordering::SeqCst) {
            break;
        }
        let seq = unsafe { GetClipboardSequenceNumber() };
        // 首次记录基准；后续对比变化
        let last = LAST_SEQ.with(|c| {
            let prev = c.get().unwrap_or(seq);
            c.set(Some(seq));
            prev
        });
        if seq == last {
            continue;
        }
        // 序列号变化：仅当变化来自本应用 copy_back（序列号精确匹配）时跳过，
        // 避免旧布尔标志在用户后续复制时被误吞。
        if let Ok(mut s) = suppress.lock() {
            if *s == Some(seq) {
                *s = None;
                continue;
            }
        }
        let (rec_text, rec_image, rec_files, max_items, max_image_kb, dedup) = {
            let s = settings.lock().unwrap_or_else(|e| e.into_inner());
            (
                s.record_text,
                s.record_image,
                s.record_files,
                s.max_items,
                s.max_image_kb,
                s.dedup,
            )
        };
        let data = match read_clipboard() {
            Some(d) => d,
            None => continue,
        };
        let item = match &data {
            ClipData::Text(t) => {
                if !rec_text {
                    continue;
                }
                build_text_item(t)
            }
            ClipData::Image { dib, width, height } => {
                if !rec_image {
                    continue;
                }
                if max_image_kb > 0 && (dib.len() as u64 / 1024) > max_image_kb {
                    continue;
                }
                build_image_item(dib, *width, *height)
            }
            ClipData::Files(fs) => {
                if !rec_files {
                    continue;
                }
                build_files_item(fs)
            }
        };
        if let Some(_id) = storage.insert_or_touch(item, dedup) {
            storage.prune_to_max(max_items);
            let _ = app.emit(crate::constants::events::CLIPBOARD_CHANGED, ());
        }
    })
}

thread_local! {
    static LAST_SEQ: std::cell::Cell<Option<u32>> = std::cell::Cell::new(None);
}

fn build_text_item(t: &str) -> NewItem {
    NewItem {
        kind: "text".into(),
        content: Some(t.to_string()),
        blob: None,
        thumb: None,
        preview: make_preview(t, 200),
        size: t.len() as i64,
        hash: hash_str(t),
    }
}

fn build_image_item(dib: &[u8], w: u32, h: u32) -> NewItem {
    NewItem {
        kind: "image".into(),
        content: None,
        blob: Some(dib.to_vec()),
        thumb: super::reader::dib_to_thumbnail(dib, 256),
        preview: format!("图片 {}×{}", w, h),
        size: dib.len() as i64,
        hash: hash_bytes(dib),
    }
}

fn build_files_item(files: &[String]) -> NewItem {
    let content = serde_json::to_string(files).unwrap_or_default();
    let preview = if files.len() == 1 {
        make_preview(&files[0], 200)
    } else {
        format!(
            "{} 个文件 · {}",
            files.len(),
            make_preview(files.first().map(|s| s.as_str()).unwrap_or(""), 60)
        )
    };
    let hash = hash_str(&content);
    NewItem {
        kind: "files".into(),
        content: Some(content),
        blob: None,
        thumb: None,
        preview,
        size: files.iter().map(|f| f.len()).sum::<usize>() as i64,
        hash,
    }
}

fn make_preview(s: &str, max_chars: usize) -> String {
    let single: String = s
        .chars()
        .map(|c| if c.is_control() { ' ' } else { c })
        .collect();
    let trimmed = single.trim().to_string();
    if trimmed.chars().count() <= max_chars {
        trimmed
    } else {
        let truncated: String = trimmed.chars().take(max_chars).collect();
        format!("{}…", truncated)
    }
}

fn hash_str(s: &str) -> String {
    use std::collections::hash_map::DefaultHasher;
    use std::hash::Hasher;
    let mut h = DefaultHasher::new();
    h.write(s.as_bytes());
    format!("{:016x}", h.finish())
}

fn hash_bytes(b: &[u8]) -> String {
    use std::collections::hash_map::DefaultHasher;
    use std::hash::Hasher;
    let mut h = DefaultHasher::new();
    h.write(b);
    format!("{:016x}", h.finish())
}