//! Note CRDT operations — create, read, mutate, and merge note documents.
//!
//! ## Data Flow
//!
//! ```text
//! Dart → note_crdt_create(id, ns, title, content) → Vec<u8>
//! Dart → db_save_crdt_doc(id, "note", bytes, ts)
//! Dart → db_load_crdt_doc(id) → Vec<u8>
//! Dart → note_crdt_read(bytes) → FfiNoteData
//! Dart → note_crdt_set_title(bytes, title) → Vec<u8>
//! ```
//!
//! Mutation functions require an active engine (HLC).  Read and merge are
//! stateless.

use chronogrid_core::NoteCrdt;

use super::state::with_engine_mut;
use super::types::FfiNoteData;

// ── Construction ─────────────────────────────────────────────────────────────

/// Creates a new note CRDT document and returns its serialized bytes.
///
/// **Requires active engine** (for HLC).
pub fn note_crdt_create(
    id: String,
    namespace_id: String,
    title: String,
    content_markdown: String,
) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note =
            NoteCrdt::new(&id, &namespace_id, &title, &content_markdown, &mut engine.hlc)
                .map_err(|e| anyhow::anyhow!("note_crdt_create failed: {e}"))?;
        Ok(note.save())
    })
}

// ── Read ─────────────────────────────────────────────────────────────────────

/// Deserializes a note CRDT document and returns a structured snapshot.
///
/// **Stateless** — does not require an active engine.
pub fn note_crdt_read(doc_bytes: Vec<u8>) -> anyhow::Result<FfiNoteData> {
    let note = NoteCrdt::from_bytes(&doc_bytes)
        .map_err(|e| anyhow::anyhow!("note_crdt_read: failed to load doc: {e}"))?;

    Ok(FfiNoteData {
        id: note.entity_id()?.unwrap_or_default(),
        namespace_id: note.namespace_id()?.unwrap_or_default(),
        project_id: note.project_id()?,
        title: note.title()?.unwrap_or_default(),
        content_markdown: note.content_markdown()?.unwrap_or_default(),
        hlc_timestamp: note.hlc_timestamp()?.unwrap_or_default(),
    })
}

// ── Field mutations ──────────────────────────────────────────────────────────

/// Sets the note title.  **Requires active engine.**
pub fn note_crdt_set_title(doc_bytes: Vec<u8>, title: String) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note = NoteCrdt::from_bytes(&doc_bytes)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        note.set_title(&title, &mut engine.hlc)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        Ok(note.save())
    })
}

/// Sets the markdown content body.
pub fn note_crdt_set_content(
    doc_bytes: Vec<u8>,
    content_markdown: String,
) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note = NoteCrdt::from_bytes(&doc_bytes)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        note.set_content_markdown(&content_markdown, &mut engine.hlc)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        Ok(note.save())
    })
}

/// Moves the note to a different project.
pub fn note_crdt_set_project_id(
    doc_bytes: Vec<u8>,
    project_id: String,
) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note = NoteCrdt::from_bytes(&doc_bytes)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        note.set_project_id(&project_id, &mut engine.hlc)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        Ok(note.save())
    })
}

/// Removes the project association.
pub fn note_crdt_clear_project_id(doc_bytes: Vec<u8>) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note = NoteCrdt::from_bytes(&doc_bytes)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        note.clear_project_id(&mut engine.hlc)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        Ok(note.save())
    })
}

/// Moves the note to a different namespace.
pub fn note_crdt_set_namespace_id(
    doc_bytes: Vec<u8>,
    namespace_id: String,
) -> anyhow::Result<Vec<u8>> {
    with_engine_mut(|engine| {
        let mut note = NoteCrdt::from_bytes(&doc_bytes)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        note.set_namespace_id(&namespace_id, &mut engine.hlc)
            .map_err(|e| anyhow::anyhow!("{e}"))?;
        Ok(note.save())
    })
}

// ── Merge ────────────────────────────────────────────────────────────────────

/// Merges two note CRDT documents and returns the combined document bytes.
///
/// **Stateless** — does not require an active engine.
pub fn note_crdt_merge(doc_a: Vec<u8>, doc_b: Vec<u8>) -> anyhow::Result<Vec<u8>> {
    let mut note_a = NoteCrdt::from_bytes(&doc_a)
        .map_err(|e| anyhow::anyhow!("note_crdt_merge: failed to load doc_a: {e}"))?;
    let mut note_b = NoteCrdt::from_bytes(&doc_b)
        .map_err(|e| anyhow::anyhow!("note_crdt_merge: failed to load doc_b: {e}"))?;

    note_a
        .merge(&mut note_b)
        .map_err(|e| anyhow::anyhow!("note_crdt_merge: merge failed: {e}"))?;

    Ok(note_a.save())
}

// ── Tests ────────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::super::engine::{close_engine, init_engine_in_memory};
    use super::super::state::engine_test_guard;
    use super::*;

    const TEST_KEY: [u8; 32] = [0xAA; 32];
    const NODE: &str = "test-node";

    fn setup() {
        let _ = close_engine();
        init_engine_in_memory(TEST_KEY.to_vec(), NODE.into()).unwrap();
    }

    fn teardown() {
        let _ = close_engine();
    }

    #[test]
    fn create_and_read_round_trip() {
        let _guard = engine_test_guard();
        setup();

        let bytes = note_crdt_create(
            "n-001".into(),
            "ns-1".into(),
            "My Note".into(),
            "# Hello World".into(),
        )
        .unwrap();

        let data = note_crdt_read(bytes).unwrap();

        assert_eq!(data.id, "n-001");
        assert_eq!(data.namespace_id, "ns-1");
        assert_eq!(data.title, "My Note");
        assert_eq!(data.content_markdown, "# Hello World");
        assert!(!data.hlc_timestamp.is_empty());

        teardown();
    }

    #[test]
    fn set_all_fields_and_read() {
        let _guard = engine_test_guard();
        setup();

        let mut bytes = note_crdt_create(
            "n-002".into(),
            "ns-1".into(),
            "Title".into(),
            "Body".into(),
        )
        .unwrap();

        bytes = note_crdt_set_title(bytes, "New Title".into()).unwrap();
        bytes = note_crdt_set_content(bytes, "## Updated\nBody text".into()).unwrap();
        bytes = note_crdt_set_project_id(bytes, "p-001".into()).unwrap();
        bytes = note_crdt_set_namespace_id(bytes, "ns-2".into()).unwrap();

        let data = note_crdt_read(bytes).unwrap();

        assert_eq!(data.title, "New Title");
        assert_eq!(data.content_markdown, "## Updated\nBody text");
        assert_eq!(data.project_id, Some("p-001".into()));
        assert_eq!(data.namespace_id, "ns-2");

        teardown();
    }

    #[test]
    fn clear_optional_fields() {
        let _guard = engine_test_guard();
        setup();

        let mut bytes = note_crdt_create(
            "n-003".into(),
            "ns-1".into(),
            "Title".into(),
            "Body".into(),
        )
        .unwrap();

        bytes = note_crdt_set_project_id(bytes, "p-1".into()).unwrap();
        bytes = note_crdt_clear_project_id(bytes).unwrap();

        let data = note_crdt_read(bytes).unwrap();
        assert_eq!(data.project_id, None);

        teardown();
    }

    #[test]
    fn merge_concurrent_edits() {
        let _guard = engine_test_guard();
        setup();

        let bytes_a = note_crdt_create(
            "n-004".into(),
            "ns-1".into(),
            "Note".into(),
            "Original".into(),
        )
        .unwrap();

        let bytes_b =
            note_crdt_set_content(bytes_a.clone(), "Peer B content".into()).unwrap();
        let bytes_a =
            note_crdt_set_content(bytes_a, "Peer A content".into()).unwrap();

        let merged = note_crdt_merge(bytes_a, bytes_b).unwrap();
        let data = note_crdt_read(merged).unwrap();

        assert!(
            data.content_markdown == "Peer A content"
                || data.content_markdown == "Peer B content",
            "merge must resolve to one of the concurrent writes, got: {}",
            data.content_markdown
        );

        teardown();
    }

    #[test]
    fn read_is_stateless() {
        let _guard = engine_test_guard();
        let _ = close_engine();

        init_engine_in_memory(TEST_KEY.to_vec(), NODE.into()).unwrap();
        let bytes = note_crdt_create(
            "n-005".into(),
            "ns-1".into(),
            "Stateless".into(),
            "Content".into(),
        )
        .unwrap();
        close_engine().unwrap();

        let data = note_crdt_read(bytes).unwrap();
        assert_eq!(data.title, "Stateless");
    }

    #[test]
    fn mutation_without_engine_fails() {
        let _guard = engine_test_guard();
        let _ = close_engine();
        let result = note_crdt_create("x".into(), "y".into(), "z".into(), "w".into());
        assert!(result.is_err());
    }
}