// Browser integration via our own miniquad JS plugin (www/dc_plugin.js):
// persistent key/value storage (localStorage), a cache that is written to storage when the
// page is hidden or closed, file download, file upload and HTTP requests.
// Native builds use simple fallbacks.

// Result of an HTTP request: status 0 means the service could not be reached
pub struct HttpResult {
    pub status: i32,
    pub body: Vec<u8>,
}

#[cfg(target_arch = "wasm32")]
mod imp {
    extern "C" {
        fn dc_storage_get(key: *const u8, key_len: u32) -> i32;
        fn dc_storage_take(dst: *mut u8);
        fn dc_storage_set(key: *const u8, key_len: u32, val: *const u8, val_len: u32);
        fn dc_cache_set(key: *const u8, key_len: u32, val: *const u8, val_len: u32);
        fn dc_download(name: *const u8, name_len: u32, data: *const u8, data_len: u32);
        fn dc_open_file();
        fn dc_file_poll() -> i32;
        fn dc_file_take(dst: *mut u8);
        fn dc_http(m: *const u8, ml: u32, u: *const u8, ul: u32, b: *const u8, bl: u32) -> u32;
        fn dc_http_poll(id: u32) -> i32;
        fn dc_http_len(id: u32) -> u32;
        fn dc_http_take(id: u32, dst: *mut u8);
    }

    // starts a request; poll the returned id with http_poll()
    pub fn http(method: &str, url: &str, body: &[u8]) -> u32 {
        unsafe { dc_http(method.as_ptr(), method.len() as u32, url.as_ptr(), url.len() as u32, body.as_ptr(), body.len() as u32) }
    }

    pub fn http_poll(id: u32) -> Option<super::HttpResult> {
        unsafe {
            let status = dc_http_poll(id);
            if status == -2 {
                return None;
            }
            let mut body = vec![0u8; dc_http_len(id) as usize];
            dc_http_take(id, body.as_mut_ptr());
            Some(super::HttpResult { status, body })
        }
    }

    pub fn storage_get(key: &str) -> Option<String> {
        unsafe {
            let n = dc_storage_get(key.as_ptr(), key.len() as u32);
            if n < 0 {
                return None;
            }
            let mut buf = vec![0u8; n as usize];
            dc_storage_take(buf.as_mut_ptr());
            String::from_utf8(buf).ok()
        }
    }

    pub fn storage_set(key: &str, val: &str) {
        unsafe { dc_storage_set(key.as_ptr(), key.len() as u32, val.as_ptr(), val.len() as u32) }
    }

    // value is written to storage by JS when the page gets hidden or closed
    pub fn cache_on_leave(key: &str, val: &str) {
        unsafe { dc_cache_set(key.as_ptr(), key.len() as u32, val.as_ptr(), val.len() as u32) }
    }

    pub fn download(name: &str, data: &[u8]) {
        unsafe { dc_download(name.as_ptr(), name.len() as u32, data.as_ptr(), data.len() as u32) }
    }

    // opens the browser file picker; poll with take_file()
    pub fn open_file() {
        unsafe { dc_open_file() }
    }

    pub fn take_file() -> Option<Vec<u8>> {
        unsafe {
            let n = dc_file_poll();
            if n < 0 {
                return None;
            }
            let mut buf = vec![0u8; n as usize];
            dc_file_take(buf.as_mut_ptr());
            Some(buf)
        }
    }
}

#[cfg(not(target_arch = "wasm32"))]
mod imp {
    use std::cell::RefCell;
    use std::collections::HashMap;
    thread_local! {
        static STORE: RefCell<HashMap<String, String>> = RefCell::new(HashMap::new());
    }
    pub fn storage_get(key: &str) -> Option<String> {
        STORE.with(|s| s.borrow().get(key).cloned())
    }
    pub fn storage_set(key: &str, val: &str) {
        STORE.with(|s| s.borrow_mut().insert(key.to_string(), val.to_string()));
    }
    pub fn cache_on_leave(key: &str, val: &str) {
        storage_set(key, val);
    }
    pub fn download(name: &str, data: &[u8]) {
        let _ = std::fs::write(name, data);
    }
    pub fn open_file() {}
    pub fn take_file() -> Option<Vec<u8>> {
        None
    }
    // no savegame service in native builds: every request fails like an unreachable server
    pub fn http(_method: &str, _url: &str, _body: &[u8]) -> u32 {
        0
    }
    pub fn http_poll(_id: u32) -> Option<super::HttpResult> {
        Some(super::HttpResult { status: 0, body: Vec::new() })
    }
}

pub use imp::*;

// Lets the JS plugin loader know this crate uses the "dungeoncraft" plugin
#[no_mangle]
pub extern "C" fn dungeoncraft_crate_version() -> u32 {
    1
}