//! Media Stats UI - Pinakes plugin
//!
//! A UI-only plugin that adds a library statistics dashboard and a tag manager
//! page. All UI definitions live in `pages/stats.json` and
//! `pages/tag-manager.json`; this WASM binary provides the minimum lifecycle
//! surface the host runtime requires.
//!
//! This plugin is kind = ["ui_page"]: no media-type, metadata, thumbnail, or
//! event-handler extension points are needed. The host will never call them,
//! but exporting them avoids linker warnings if the host performs capability
//! discovery via symbol inspection.

#![no_std]

extern crate alloc;

use core::alloc::Layout;

#[global_allocator]
static ALLOC: dlmalloc::GlobalDlmalloc = dlmalloc::GlobalDlmalloc;

#[panic_handler]
fn panic(_: &core::panic::PanicInfo) -> ! {
  core::arch::wasm32::unreachable()
}

// Host functions provided by the Pinakes runtime.
unsafe extern "C" {
  // Write a result value back to the host (ptr + byte length).
  fn host_set_result(ptr: i32, len: i32);

  // Emit a structured log message to the host logger.
  // `level` mirrors tracing severity: 0=trace 1=debug 2=info 3=warn 4=error
  fn host_log(level: i32, ptr: i32, len: i32);
}

/// # Safety
///
/// `json` is a valid slice; the host copies the bytes before
/// returning so there are no lifetime concerns.
fn set_response(json: &[u8]) {
  unsafe { host_set_result(json.as_ptr() as i32, json.len() as i32) }
}

/// # Safety
///
///  Same as [`set_response`]
fn log_info(msg: &[u8]) {
  unsafe { host_log(2, msg.as_ptr() as i32, msg.len() as i32) }
}

/// Allocate a buffer for the host to write request data into.
///
/// # Returns
///
/// The byte offset of the allocation, or -1 on failure.
///
/// # Safety
///
/// Size is positive; Layout construction cannot fail for align=1.
#[unsafe(no_mangle)]
pub extern "C" fn alloc(size: i32) -> i32 {
  if size <= 0 {
    return 0;
  }
  unsafe {
    let layout = Layout::from_size_align_unchecked(size as usize, 1);
    let ptr = alloc::alloc::alloc(layout);
    if ptr.is_null() { -1 } else { ptr as i32 }
  }
}

/// Called once after the plugin is loaded. Returns 0 on success.
#[unsafe(no_mangle)]
pub extern "C" fn initialize() -> i32 {
  log_info(b"media-stats-ui: initialized");
  0
}

/// Called before the plugin is unloaded. Returns 0 on success.
#[unsafe(no_mangle)]
pub extern "C" fn shutdown() -> i32 {
  log_info(b"media-stats-ui: shutdown");
  0
}

/// # Returns
///
/// an empty JSON array; this plugin adds no custom media types.
#[unsafe(no_mangle)]
pub extern "C" fn supported_media_types(_ptr: i32, _len: i32) {
  set_response(b"[]");
}

/// # Returns
///
/// An empty JSON array; this plugin handles no event types.
#[unsafe(no_mangle)]
pub extern "C" fn interested_events(_ptr: i32, _len: i32) {
  set_response(b"[]");
}