// Oak Video Editor - Non-Linear Video Editor
// Copyright (C) 2026 Oak Team
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! Render-side project copy client (the C++ ProjectCopier, inverted):
//! all copying happens inside oaknode. oaknode never implemented the
//! deep-copy direction (single-lib plan §4.1 — dead direction), so the
//! copy operations fail explainably; the tests assert those failures.
//!
//! M14 R5: the module is entirely internal to oakrender (no facade entry
//! is involved), so the oaknode project handle was reduced to its numeric
//! identity — a Rust value type instead of a `CHandle`. The live project
//! object stays with oaknode; the render side stores only identity pairs
//! (see `COVERAGE.md`, "render 只存 identity 对").

use crate::error::{Error, Result};

/// An opaque identity for an oaknode project (the C++ handle's `ctx`
/// reduced to its numeric value). oaknode owns the live project and
/// maintains the identity map; this module never holds the object, so no
/// lifetime management is required.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct ProjectHandle(u64);

impl ProjectHandle {
	/// New identity; `0` is the empty handle.
	pub fn new(identity: u64) -> Self {
		ProjectHandle(identity)
	}

	/// The empty handle (no project attached).
	pub fn null() -> Self {
		ProjectHandle(0)
	}

	/// True for the empty handle.
	pub fn is_null(self) -> bool {
		self.0 == 0
	}

	/// The raw identity value.
	pub fn as_u64(self) -> u64 {
		self.0
	}
}

/// One change record (see oaknode `ChangeRecord`).
#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct ChangeRecord {
	/// Discriminant (see oaknode `ChangeRecord`).
	pub kind: u32,
	/// Payload bytes (per-kind layout documented in project.h).
	pub payload: [u8; 48],
}

/// Change-record discriminants (oaknode project.h).
pub mod change_kind {
	/// Node added.
	pub const NODE_ADD: u32 = 0;
	/// Node removed.
	pub const NODE_REMOVE: u32 = 1;
	/// Edge added.
	pub const EDGE_ADD: u32 = 2;
	/// Edge removed.
	pub const EDGE_REMOVE: u32 = 3;
	/// Value change.
	pub const VALUE_CHANGE: u32 = 4;
	/// Value hint change.
	pub const VALUE_HINT_CHANGE: u32 = 5;
	/// Project setting change.
	pub const PROJECT_SETTING_CHANGE: u32 = 6;
	/// Footage proxy change.
	pub const FOOTAGE_PROXY: u32 = 7;
}

/// `oaknode_project_deep_copy(project)` — would return an owned
/// copied-project handle.
///
/// Never implemented: oaknode has no such Rust function (single-lib plan
/// §4.1 — dead direction), so this always yields the empty handle, exactly
/// as the previous runtime-symbol lookup did when the symbol was absent.
pub fn project_deep_copy(_project: ProjectHandle) -> ProjectHandle {
	ProjectHandle::null()
}

/// `oaknode_project_sync_copy` — never implemented (dead direction); the
/// sync always fails explainably.
pub fn project_sync_copy(
	_source: ProjectHandle,
	_copy: ProjectHandle,
	_changes: &[ChangeRecord],
) -> Result<()> {
	Err(Error::Failed(
		"oaknode_project_sync_copy missing (not implemented in oaknode)".into(),
	))
}

/// A render-side project copy (identity only — the copy's live object
/// stays with oaknode).
pub struct ProjectCopy {
	/// Identity of the source project.
	pub source: u64,
	/// Identity of the copied project (0 = no copy attached).
	pub copy: u64,
	/// Change-generation counter of the last successful sync.
	pub last_sync_generation: u64,
	/// True while recorded changes await `sync`.
	pub has_pending_updates: bool,
}

impl ProjectCopy {
	/// A copier with no project attached yet (C++ `ProjectCopier()`).
	pub fn new() -> Self {
		Self {
			source: 0,
			copy: 0,
			last_sync_generation: 0,
			has_pending_updates: false,
		}
	}

	/// Create a deep copy of `source` through oaknode (C++
	/// `ProjectCopier::set_project`).
	pub fn set_project(&mut self, source: ProjectHandle) -> Result<()> {
		if source.is_null() {
			return Err(Error::Invalid);
		}
		// Drop any previous copy.
		self.release_copy();
		let copy = crate::copier::project_deep_copy(source);
		if copy.is_null() {
			return Err(Error::Failed(
				"oaknode_project_deep_copy failed (symbol missing or copy error)".into(),
			));
		}
		self.source = source.as_u64();
		self.copy = copy.as_u64();
		self.last_sync_generation = 0;
		self.has_pending_updates = false;
		Ok(())
	}

	/// Push a recorded change set into the copy (C++
	/// ProjectCopier::process_update_queue).
	pub fn sync(&mut self, changes: &[ChangeRecord]) -> Result<()> {
		if self.copy == 0 {
			return Err(Error::State);
		}
		crate::copier::project_sync_copy(
			ProjectHandle::new(self.source),
			ProjectHandle::new(self.copy),
			changes,
		)?;
		self.last_sync_generation += 1;
		self.has_pending_updates = false;
		Ok(())
	}

	/// The copied project's identity (borrowed for the caller).
	pub fn copied_project(&self) -> Option<ProjectHandle> {
		if self.copy == 0 {
			None
		} else {
			Some(ProjectHandle::new(self.copy))
		}
	}

	/// The copied counterpart of an original node — requires the oaknode
	/// node-map query (`oaknode_project_copy_of_node`), which is part of
	/// the pending node bridge; returns `None` until then.
	pub fn copy_of_node(&self, _original: u64) -> Option<u64> {
		None
	}

	/// Drop the copy (forgets its identity).
	pub fn destroy(&mut self) {
		self.release_copy();
	}

	fn release_copy(&mut self) {
		self.copy = 0;
	}
}

impl Default for ProjectCopy {
	fn default() -> Self {
		Self::new()
	}
}

#[cfg(test)]
mod tests {
	use super::*;

	#[test]
	fn fresh_copier_has_no_copy() {
		let pc = ProjectCopy::new();
		assert_eq!(pc.source, 0);
		assert_eq!(pc.copy, 0);
		assert!(pc.copied_project().is_none());
		assert!(!pc.has_pending_updates);
	}

	#[test]
	fn set_project_rejects_empty_handle() {
		let mut pc = ProjectCopy::new();
		assert_eq!(
			pc.set_project(ProjectHandle::null()).unwrap_err().code(),
			Error::Invalid.code()
		);
	}

	#[test]
	fn set_project_with_valid_identity_fails() {
		// oaknode never implemented the deep-copy direction; even a valid
		// identity cannot be copied, and the copier fails explainably.
		let mut pc = ProjectCopy::new();
		assert_eq!(
			pc.set_project(ProjectHandle::new(1)).unwrap_err().code(),
			Error::Failed(String::new()).code()
		);
		assert_eq!(pc.copy, 0);
		assert!(pc.copied_project().is_none());
	}

	#[test]
	fn sync_without_project_is_state_error() {
		let mut pc = ProjectCopy::new();
		let changes = [ChangeRecord {
			kind: crate::copier::change_kind::NODE_ADD,
			payload: [0u8; 48],
		}];
		assert_eq!(pc.sync(&changes).unwrap_err().code(), Error::State.code());
	}

	#[test]
	fn destroy_releases_cleanly() {
		let mut pc = ProjectCopy::new();
		pc.destroy();
		assert_eq!(pc.copy, 0);
	}
}