//! Defines the data structures used for describing instance patches.

use std::{collections::HashSet, path::PathBuf};

use rbx_dom_weak::{
    types::{Ref, Variant},
    HashMapExt as _, Ustr, UstrMap,
};
use serde::{Deserialize, Serialize};

use super::{InstanceMetadata, InstanceSnapshot};

/// A set of different kinds of patches that can be applied to an WeakDom.
///
/// These patches shouldn't be persisted: there's no mechanism in place to make
/// sure that another patch wasn't applied before this one that could cause a
/// conflict!
#[derive(Debug, Default, Clone, PartialEq, Serialize, Deserialize)]
pub struct PatchSet {
    pub removed_instances: Vec<Ref>,
    pub added_instances: Vec<PatchAdd>,
    pub updated_instances: Vec<PatchUpdate>,
    /// Instance IDs whose backing files should be staged via git add after writing.
    /// Populated from WriteRequest.stage_ids, consumed by change_processor.
    #[serde(default, skip)]
    pub stage_ids: HashSet<Ref>,
    /// Pre-resolved filesystem paths to stage via git add.
    /// Populated by api.rs (for files already on disk), consumed by change_processor
    /// together with any Source write paths from stage_ids.
    /// All staging is consolidated into a single git_add call to avoid index.lock races.
    #[serde(default, skip)]
    pub stage_paths: Vec<std::path::PathBuf>,
}

impl PatchSet {
    pub fn new() -> Self {
        PatchSet {
            removed_instances: Vec::new(),
            added_instances: Vec::new(),
            updated_instances: Vec::new(),
            stage_ids: HashSet::new(),
            stage_paths: Vec::new(),
        }
    }
}

/// A patch containing an instance that was added to the tree.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct PatchAdd {
    pub parent_id: Ref,
    pub instance: InstanceSnapshot,
}

/// A patch indicating that properties of an instance changed.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct PatchUpdate {
    pub id: Ref,
    pub changed_name: Option<String>,
    pub changed_class_name: Option<Ustr>,

    /// Contains all changed properties. If a property is assigned to `None`,
    /// then that property has been removed.
    pub changed_properties: UstrMap<Option<Variant>>,

    /// Changed Rojo-specific metadata, if any of it changed.
    pub changed_metadata: Option<InstanceMetadata>,
}

/// Applied patch sets have the same rough shape as PatchSet, but are
/// descriptive of the operation that happened instead of prescribing what
/// mutations to apply to the tree.
///
/// Applied patch sets are generated by applying a patch to a tree, and are
/// suitable for sending over the network to a synchronized tree like the Rojo
/// Studio plugin.
///
// TODO: Introduce machinery to detect conflicts, like keeping previous +
// current values in all fields.
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct AppliedPatchSet {
    pub removed: Vec<Ref>,
    pub added: Vec<Ref>,
    pub updated: Vec<AppliedPatchUpdate>,

    /// Collected during patch application: `(resolved_absolute_ref_path, meta_or_model_file_path)`.
    /// Used to build `RefPathIndex` without re-walking the directory tree.
    #[serde(skip)]
    pub ref_path_index_entries: Vec<(String, PathBuf)>,
}

impl AppliedPatchSet {
    pub fn new() -> Self {
        AppliedPatchSet {
            removed: Vec::new(),
            added: Vec::new(),
            updated: Vec::new(),
            ref_path_index_entries: Vec::new(),
        }
    }

    pub fn is_empty(&self) -> bool {
        self.removed.is_empty() && self.added.is_empty() && self.updated.is_empty()
    }

    /// Merge multiple patch sets into a single consolidated set.
    ///
    /// Different platforms deliver VFS events in different orders for the
    /// same filesystem operation (e.g., macOS FSEvents sends CREATE first,
    /// Windows ReadDirectoryChangesW sends REMOVE first for renames).
    /// Merging ensures the WebSocket message structure is identical
    /// regardless of event ordering.
    pub fn merge(patches: Vec<AppliedPatchSet>) -> AppliedPatchSet {
        let mut merged = AppliedPatchSet::new();
        for patch in patches {
            merged.removed.extend(patch.removed);
            merged.added.extend(patch.added);
            merged.updated.extend(patch.updated);
        }
        merged
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AppliedPatchUpdate {
    pub id: Ref,

    // TODO: Store previous values in order to detect application conflicts
    pub changed_name: Option<String>,
    pub changed_class_name: Option<Ustr>,
    pub changed_properties: UstrMap<Option<Variant>>,
    pub changed_metadata: Option<InstanceMetadata>,
}

impl AppliedPatchUpdate {
    pub fn new(id: Ref) -> Self {
        Self {
            id,
            changed_name: None,
            changed_class_name: None,
            changed_properties: UstrMap::new(),
            changed_metadata: None,
        }
    }
}