use crate::model::Model;
use std::collections::HashSet;

/// A flattened entry in the category panel tree.
#[derive(Debug, Clone)]
pub enum CatTreeEntry {
    /// Category header row: name, item count, expanded?
    Category {
        name: String,
        item_count: usize,
        expanded: bool,
    },
    /// Item row under a category
    Item { cat_name: String, item_name: String },
}

impl CatTreeEntry {
    /// The category this entry belongs to.
    pub fn cat_name(&self) -> &str {
        match self {
            CatTreeEntry::Category { name, .. } => name,
            CatTreeEntry::Item { cat_name, .. } => cat_name,
        }
    }
}

/// Build the flattened tree of categories and their items.
pub fn build_cat_tree(model: &Model, expanded: &HashSet<String>) -> Vec<CatTreeEntry> {
    let mut entries = Vec::new();
    for cat_name in model.category_names() {
        let cat = model.category(cat_name);
        let item_count = cat.map(|c| c.items.len()).unwrap_or(0);
        let is_expanded = expanded.contains(cat_name);
        entries.push(CatTreeEntry::Category {
            name: cat_name.to_string(),
            item_count,
            expanded: is_expanded,
        });
        if is_expanded {
            if let Some(cat) = cat {
                for item_name in cat.ordered_item_names() {
                    entries.push(CatTreeEntry::Item {
                        cat_name: cat_name.to_string(),
                        item_name: item_name.to_string(),
                    });
                }
            }
        }
    }
    entries
}