use std::collections::HashMap;
use std::collections::HashSet;
use std::sync::Arc;


use crate::{Graph, Reference, random_object};

fn get_deterministic_candidate(graph: &Graph) -> Arc<Reference> {
    // Pick a deterministic leaf node to update (first lexicographically)
    let mut refs: Vec<Arc<Reference>> = graph.refs.values()
        .filter(|r| r.name != graph.root.name && r.is_leaf())
        .map(|r| r.clone())
        .collect();
    
    // Sort by name to ensure deterministic ordering
    refs.sort_by(|a, b| a.name.cmp(&b.name));
    
    refs[0].clone()
}

/// Tests that all dependencies are kept updated when new nodes are added
#[test]
fn test_dependencies_updated_when_nodes_added() {
    // Create a simple graph
    let mut graph = create_test_graph();
    
    // Get the initial content address of the root
    let initial_root_id = graph.root.id.clone();
    
    let candidate = get_deterministic_candidate(&graph);
    
    // Update the leaf node with deterministic content
    let new_content = b"deterministic_test_content".to_vec();
    graph.update_object_reference(&candidate.name, new_content).unwrap();
    
    // Verify that the leaf node's ID has changed
    let updated_leaf = graph.get_reference(&candidate.name).unwrap();
    assert_ne!(updated_leaf.id, candidate.id,
        "Leaf node ID should change when content is updated");
    
    // Verify that the root's ID has changed
    assert_ne!(graph.root.id, initial_root_id, 
        "Root ID should change when a dependent node is updated");
    
}

/// Tests that the root of the graph is not itself a dependency of any other node
#[test]
fn test_root_not_a_dependency() {
    let graph = create_test_graph();
    let root_name = graph.root.name.clone();
    
    // Check all references to ensure none have the root as a dependent
    for (_, reference) in graph.refs.as_ref() {
        for dep in &reference.dependents {
            assert_ne!(dep.name, root_name, 
                "Root should not be a dependency of any other node");
        }
    }
}

/// Tests that all nodes are dependents or transitive dependents of the root
#[test]
fn test_all_nodes_connected_to_root() {
    let graph = create_test_graph();
    
    // Collect all nodes reachable from the root
    let mut reachable = HashSet::new();
    
    fn collect_reachable(node: &Arc<Reference>, reachable: &mut HashSet<String>) {
        reachable.insert(node.name.clone());
        
        for dep in &node.dependents {
            if !reachable.contains(&dep.name) {
                collect_reachable(dep, reachable);
            }
        }
    }
    
    collect_reachable(&graph.root, &mut reachable);
    
    // Check that all nodes in the graph are reachable from the root
    for (name, _) in graph.refs.as_ref() {
        assert!(reachable.contains(name), 
            "All nodes should be reachable from the root: {}", name);
    }
}

/// Helper function to create a test graph with a known structure
fn create_test_graph() -> Graph {
    let root_name = String::from("/root");
    let mut objects = HashMap::new();
    let mut refs = HashMap::new();
    
    // Create the root reference
    let mut root_ref = Reference::new(
        Some(String::from("root_content")),
        root_name.clone(),
    );
    
    // Create 3 item references
    for i in 1..=3 {
        let item_name = format!("/item/{}", i);
        let mut item_ref = Reference::new(
            Some(format!("item_content_{}", i)),
            item_name.clone(),
        );
        
        // Create 3 subitems for each item
        for j in 1..=3 {
            let (address, content) = random_object();
            let subitem_name = format!("/item/{}/subitem/{}", i, j);
            
            // Create a leaf reference
            let leaf_ref = Reference::new(
                Some(address.clone()),
                subitem_name,
            ).to_arc();
            
            // Add the leaf reference as a dependent to the item reference
            item_ref = item_ref.add_dep(leaf_ref.clone());
            
            // Store the content in the objects map
            objects.insert(address.clone(), content);
            
            // Store the leaf reference in the refs map
            refs.insert(leaf_ref.name.clone(), leaf_ref);
        }
        
        // Convert the item reference to Arc and add it to the root reference
        let arc_item_ref = item_ref.to_arc();
        root_ref = root_ref.add_dep(arc_item_ref.clone());
        
        // Store the item reference in the refs map
        refs.insert(arc_item_ref.name.clone(), arc_item_ref);
    }
    
    // Convert the root reference to Arc
    let arc_root_ref = root_ref.to_arc();
    
    // Store the root reference in the refs map
    refs.insert(arc_root_ref.name.clone(), arc_root_ref.clone());
    
    Graph {
        root: arc_root_ref,
        refs: Arc::new(refs),
        objects: Arc::new(objects),
    }
}

/// Tests that the graph correctly handles content-addressable properties
#[test]
fn test_content_addressable_properties() {
    let mut graph = create_test_graph();
    
    // Update a leaf node with the same content
    let leaf_path = "/item/1/subitem/1".to_string();
    let initial_leaf = graph.get_reference(&leaf_path).unwrap();
    if let Some(content_address) = initial_leaf.content_address.clone() {
        // Get the content for this address
        let content = graph.get_object(&content_address).unwrap().clone();
        
        // Update with the same content
        graph.update_object_reference(&leaf_path, content).unwrap();
    }
    
    // Verify that nothing changed since the content is the same
    let updated_leaf = graph.get_reference(&leaf_path).unwrap();
    assert_eq!(updated_leaf.content_address, initial_leaf.content_address,
        "Content address should not change when content remains the same");
}

/// Tests that the graph correctly handles ID calculation
#[test]
fn test_id_calculation() {
    let mut graph = create_test_graph();
    
    // Update a leaf node
    let leaf_path = "/item/1/subitem/1".to_string();
    let initial_leaf = graph.get_reference(&leaf_path).unwrap();
    
    graph.update_object_reference(&leaf_path, "new content".as_bytes().to_vec()).unwrap();
    
    // Verify that the ID changed
    let updated_leaf = graph.get_reference(&leaf_path).unwrap();
    assert_ne!(updated_leaf.id, initial_leaf.id,
        "Reference ID should change when content changes");
    
    // Verify that parent ID changed
    let parent_path = "/item/1".to_string();
    let parent = graph.get_reference(&parent_path).unwrap();
    
    // Create a reference with the same properties to calculate expected ID
    let mut test_ref = Reference::new(
        parent.content_address.clone(),
        parent.name.clone(),
    );
    
    // Add the same dependents
    for dep in &parent.dependents {
        test_ref = test_ref.add_dep(dep.clone());
    }
    
    // Verify the ID calculation is consistent
    assert_eq!(parent.id, test_ref.id,
        "ID calculation should be consistent for the same reference properties");
}

/// Tests that the root ID always changes when any reference is updated
#[test]
fn test_root_id_changes_for_any_reference_update() {
    let mut graph = create_test_graph();
    
    // Get all non-root references sorted by name for deterministic iteration
    let mut all_refs: Vec<(String, String)> = graph.refs.as_ref()
        .iter()
        .filter(|(name, _)| **name != graph.root.name)
        .map(|(name, ref_arc)| (name.clone(), ref_arc.id.clone()))
        .collect();
    
    all_refs.sort_by(|a, b| a.0.cmp(&b.0));
    
    // Test each reference update
    for (ref_name, original_ref_id) in all_refs {
        // Record the current root ID
        let initial_root_id = graph.root.id.clone();
        
        // Update the reference with new content
        let new_content = format!("updated_content_for_{}", ref_name).into_bytes();
        graph.update_object_reference(&ref_name, new_content).unwrap();
        
        // Verify the reference itself changed
        let updated_ref = graph.get_reference(&ref_name).unwrap();
        assert_ne!(updated_ref.id, original_ref_id,
            "Reference {} should have changed ID after update", ref_name);
        
        // Verify the root ID changed
        assert_ne!(graph.root.id, initial_root_id,
            "Root ID should change when reference {} is updated", ref_name);
    }
}

/// Tests that Reference IDs are stable regardless of dependency add order
#[test]
fn test_reference_ids_stable_regardless_of_dependency_order() {
    // Create test dependencies
    let dep_a = Reference::new(
        Some(String::from("content_a")),
        String::from("/dep_a"),
    ).to_arc();
    
    let dep_b = Reference::new(
        Some(String::from("content_b")),
        String::from("/dep_b"),
    ).to_arc();
    
    let dep_c = Reference::new(
        Some(String::from("content_c")),
        String::from("/dep_c"),
    ).to_arc();
    
    let dep_d = Reference::new(
        Some(String::from("content_d")),
        String::from("/dep_d"),
    ).to_arc();
    
    // Create base reference
    let base_ref = Reference::new(
        Some(String::from("base_content")),
        String::from("/base"),
    );
    
    // Test multiple different orders of adding the same dependencies
    let orders = vec![
        vec![dep_a.clone(), dep_b.clone(), dep_c.clone(), dep_d.clone()],  // alphabetical
        vec![dep_d.clone(), dep_c.clone(), dep_b.clone(), dep_a.clone()],  // reverse alphabetical
        vec![dep_b.clone(), dep_d.clone(), dep_a.clone(), dep_c.clone()],  // random order 1
        vec![dep_c.clone(), dep_a.clone(), dep_d.clone(), dep_b.clone()],  // random order 2
        vec![dep_d.clone(), dep_a.clone(), dep_b.clone(), dep_c.clone()],  // random order 3
    ];
    
    let mut all_ids = Vec::new();
    
    for (i, order) in orders.iter().enumerate() {
        let mut test_ref = base_ref.clone();
        
        // Add dependencies in this specific order
        for dep in order {
            test_ref = test_ref.add_dep(dep.clone());
        }
        
        all_ids.push(test_ref.id.clone());
        
        // Verify that dependencies are always sorted lexicographically regardless of add order
        for j in 0..test_ref.dependents.len() - 1 {
            let current = &test_ref.dependents[j];
            let next = &test_ref.dependents[j + 1];
            
            assert!(current.name < next.name, 
                "Dependencies should be lexicographically ordered. Order {}: Found '{}' before '{}'", 
                i, current.name, next.name);
        }
    }
    
    // Verify all IDs are identical
    let first_id = &all_ids[0];
    for (i, id) in all_ids.iter().enumerate() {
        assert_eq!(id, first_id, 
            "Reference ID should be stable regardless of dependency add order. Order {} produced different ID", i);
    }
}

/// Tests that dependencies of a Reference are always lexicographically ordered by name
#[test]
fn test_dependencies_lexicographically_ordered() {
    let graph = create_test_graph();
    
    // Check all references to ensure their dependents are lexicographically ordered
    for (_, reference) in graph.refs.as_ref() {
        if reference.dependents.len() > 1 {
            // Check that dependents are ordered by name
            for i in 0..reference.dependents.len() - 1 {
                let current = &reference.dependents[i];
                let next = &reference.dependents[i + 1];
                
                assert!(current.name < next.name, 
                    "Dependencies should be lexicographically ordered by name. Found '{}' before '{}'", 
                    current.name, next.name);
            }
        }
    }
    
    // Also verify that when we add dependencies, they maintain the correct order
    let mut test_ref = Reference::new(
        Some(String::from("test_content")),
        String::from("/test_ordering"),
    );
    
    // Add dependencies in non-lexicographical order
    let dep_c = Reference::new(
        Some(String::from("c_content")),
        String::from("/c"),
    ).to_arc();
    
    let dep_a = Reference::new(
        Some(String::from("a_content")),
        String::from("/a"),
    ).to_arc();
    
    let dep_b = Reference::new(
        Some(String::from("b_content")),
        String::from("/b"),
    ).to_arc();
    
    // Add in non-lexicographical order
    test_ref = test_ref.add_dep(dep_c.clone());
    test_ref = test_ref.add_dep(dep_a.clone());
    test_ref = test_ref.add_dep(dep_b.clone());
    
    // Verify they are stored in lexicographical order
    assert_eq!(test_ref.dependents[0].name, "/a", "First dependent should be '/a'");
    assert_eq!(test_ref.dependents[1].name, "/b", "Second dependent should be '/b'");
    assert_eq!(test_ref.dependents[2].name, "/c", "Third dependent should be '/c'");
}