//! Unity YAML parsing module

pub mod guid_resolver;
pub mod meta;
pub mod prefab_guid_resolver;
mod unity_tag;
mod yaml;

pub use guid_resolver::{find_project_root, GuidResolver};
pub use meta::{get_meta_path, MetaFile};
pub use prefab_guid_resolver::PrefabGuidResolver;
pub use unity_tag::{parse_unity_tag, UnityTag};
pub use yaml::split_yaml_documents;

use log::{info, warn};

use crate::model::{RawDocument, UnityAsset, UnityFile, UnityPrefab, UnityScene, UnityProject};
use crate::types::{FileID, Guid, TypeFilter};
use crate::{Error, Result};
use regex::Regex;
use std::path::Path;

/// Parse a Unity file from the given path
///
/// Automatically detects file type based on extension:
/// - .unity → UnityFile::Scene with ECS World
/// - .prefab → UnityFile::Prefab with raw YAML
/// - .asset → UnityFile::Asset with raw YAML
///
/// By default, parses all files. Use `parse_unity_file_filtered` for regex filtering.
///
/// # Example
///
/// ```no_run
/// use unity_parser::parser::parse_unity_file;
/// use unity_parser::UnityFile;
/// use std::path::Path;
///
/// let file = parse_unity_file(Path::new("Scene.unity"))?;
/// match file {
///     UnityFile::Scene(scene) => println!("Scene with {} entities", scene.entity_map.len()),
///     UnityFile::Prefab(prefab) => println!("Prefab with {} documents", prefab.documents.len()),
///     UnityFile::Asset(asset) => println!("Asset with {} documents", asset.documents.len()),
/// }
/// # Ok::<(), unity_parser::Error>(())
/// ```
pub fn parse_unity_file(path: &Path) -> Result<UnityFile> {
    parse_unity_file_filtered(path, None, None)
}

/// Parse a Unity file with optional regex filtering and type filtering
///
/// Same as `parse_unity_file`, but allows filtering files by path pattern and Unity types.
/// If the path doesn't match the regex, returns an error.
///
/// # Arguments
///
/// * `path` - Path to the Unity file to parse
/// * `filter` - Optional regex to match against the file path. If None, parses all files (default behavior).
/// * `type_filter` - Optional filter for Unity types and MonoBehaviour GUIDs. If None, parses all types (default behavior).
///
/// # Example
///
/// ```no_run
/// use unity_parser::parser::{parse_unity_file_filtered};
/// use unity_parser::TypeFilter;
/// use regex::Regex;
/// use std::path::Path;
/// use std::collections::HashSet;
///
/// // Only parse files with "Test" in the name
/// let filter = Regex::new(r"Test").unwrap();
/// let file = parse_unity_file_filtered(Path::new("TestScene.unity"), Some(&filter), None)?;
///
/// // Only parse Transform and GameObject types
/// let mut types = HashSet::new();
/// types.insert("Transform".to_string());
/// types.insert("GameObject".to_string());
/// let type_filter = TypeFilter::with_unity_types(types);
/// let file2 = parse_unity_file_filtered(Path::new("Scene.unity"), None, Some(&type_filter))?;
/// # Ok::<(), unity_parser::Error>(())
/// ```
pub fn parse_unity_file_filtered(
    path: &Path,
    filter: Option<&Regex>,
    type_filter: Option<&TypeFilter>,
) -> Result<UnityFile> {
    // Apply filter if provided
    if let Some(regex) = filter {
        let path_str = path.to_str().ok_or_else(|| {
            Error::invalid_format("Path contains invalid UTF-8")
        })?;

        if !regex.is_match(path_str) {
            return Err(Error::invalid_format(format!(
                "Path '{}' does not match filter pattern",
                path.display()
            )));
        }
    }

    parse_unity_file_impl(path, type_filter)
}

/// Internal implementation of Unity file parsing
fn parse_unity_file_impl(path: &Path, type_filter: Option<&TypeFilter>) -> Result<UnityFile> {
    // Read the file
    let content = std::fs::read_to_string(path)?;

    // Validate Unity header
    validate_unity_header(&content, path)?;

    // Detect file type by extension
    let file_type = detect_file_type(path);

    // Parse based on file type
    match file_type {
        FileType::Scene => parse_scene(path, &content, type_filter),
        FileType::Prefab => parse_prefab(path, &content, type_filter),
        FileType::Asset => parse_asset(path, &content, type_filter),
        FileType::Unknown => Err(Error::invalid_format(format!(
            "Unknown file extension: {}",
            path.display()
        ))),
    }
}

/// File type enumeration
enum FileType {
    Scene,
    Prefab,
    Asset,
    Unknown,
}

/// Detect file type based on extension
fn detect_file_type(path: &Path) -> FileType {
    match path.extension().and_then(|s| s.to_str()) {
        Some("unity") => FileType::Scene,
        Some("prefab") => FileType::Prefab,
        Some("asset") => FileType::Asset,
        _ => FileType::Unknown,
    }
}

/// Parse a scene file into an ECS World
fn parse_scene(path: &Path, content: &str, type_filter: Option<&TypeFilter>) -> Result<UnityFile> {
    let raw_documents = parse_raw_documents(content, type_filter)?;

    // Try to find Unity project root and build both GUID resolvers
    let (guid_resolver, prefab_guid_resolver) = match find_project_root(path) {
        Ok(project_root) => {
            info!("📦 Found Unity project root: {}", project_root.display());

            // Build script GUID resolver
            let guid_res = match GuidResolver::from_project(&project_root) {
                Ok(resolver) => {
                    info!("Script GUID resolver built ({} mappings)", resolver.len());
                    Some(resolver)
                }
                Err(e) => {
                    warn!("Failed to build script GUID resolver: {}", e);
                    None
                }
            };

            // Build prefab GUID resolver
            let prefab_res = match PrefabGuidResolver::from_project(&project_root) {
                Ok(resolver) => {
                    info!("Prefab GUID resolver built ({} mappings)", resolver.len());
                    Some(resolver)
                }
                Err(e) => {
                    warn!("Failed to build prefab GUID resolver: {}", e);
                    None
                }
            };

            (guid_res, prefab_res)
        }
        Err(_) => {
            // Not part of a Unity project, or project root not found
            (None, None)
        }
    };

    // Build ECS world from documents with both resolvers
    let (world, entity_map) = crate::ecs::build_world_from_documents(
        raw_documents,
        guid_resolver.as_ref(),
        prefab_guid_resolver.as_ref(),
    )?;

    Ok(UnityFile::Scene(UnityScene::new(
        path.to_path_buf(),
        world,
        entity_map,
    )))
}

/// Parse a scene file using pre-built GUID resolvers from a UnityProject
///
/// This is more efficient than `parse_scene` when parsing multiple scenes
/// because the GUID resolvers are already initialized.
///
/// # Arguments
///
/// * `path` - Path to the scene file
/// * `project` - Pre-initialized UnityProject with GUID resolvers
pub fn parse_scene_with_project(path: &Path, project: &UnityProject) -> Result<UnityScene> {
    parse_scene_with_project_filtered(path, project, None)
}

/// Parse a scene file using pre-built GUID resolvers from a UnityProject with optional type filtering
///
/// # Arguments
///
/// * `path` - Path to the scene file
/// * `project` - Pre-initialized UnityProject with GUID resolvers
/// * `type_filter` - Optional filter for Unity types and MonoBehaviour class names
pub fn parse_scene_with_project_filtered(
    path: &Path,
    project: &UnityProject,
    type_filter: Option<&TypeFilter>
) -> Result<UnityScene> {
    // Read the file
    let content = std::fs::read_to_string(path)?;

    // Validate Unity header
    validate_unity_header(&content, path)?;

    // Parse raw documents with type filtering
    let raw_documents = parse_raw_documents(&content, type_filter)?;

    // Build ECS world from documents using project's resolvers
    let (world, entity_map) = crate::ecs::build_world_from_documents(
        raw_documents,
        Some(&project.guid_resolver),
        Some(&project.prefab_resolver),
    )?;

    Ok(UnityScene::new(
        path.to_path_buf(),
        world,
        entity_map,
    ))
}

/// Parse a prefab file using pre-built GUID resolvers from a UnityProject
///
/// # Arguments
///
/// * `path` - Path to the prefab file
/// * `project` - Pre-initialized UnityProject with GUID resolvers
pub fn parse_prefab_with_project(path: &Path, _project: &UnityProject) -> Result<UnityPrefab> {
    // Read the file
    let content = std::fs::read_to_string(path)?;

    // Validate Unity header
    validate_unity_header(&content, path)?;

    // Parse raw documents
    let raw_documents = parse_raw_documents(&content, None)?;

    Ok(UnityPrefab::new(
        path.to_path_buf(),
        raw_documents,
    ))
}

/// Parse an asset file using pre-built GUID resolvers from a UnityProject
///
/// # Arguments
///
/// * `path` - Path to the asset file
/// * `project` - Pre-initialized UnityProject with GUID resolvers
pub fn parse_asset_with_project(path: &Path, _project: &UnityProject) -> Result<UnityAsset> {
    // Read the file
    let content = std::fs::read_to_string(path)?;

    // Validate Unity header
    validate_unity_header(&content, path)?;

    // Parse raw documents
    let raw_documents = parse_raw_documents(&content, None)?;

    Ok(UnityAsset::new(
        path.to_path_buf(),
        raw_documents,
    ))
}

/// Parse a prefab file into raw YAML documents
fn parse_prefab(path: &Path, content: &str, type_filter: Option<&TypeFilter>) -> Result<UnityFile> {
    let raw_documents = parse_raw_documents(content, type_filter)?;

    Ok(UnityFile::Prefab(UnityPrefab::new(
        path.to_path_buf(),
        raw_documents,
    )))
}

/// Parse an asset file into raw YAML documents
fn parse_asset(path: &Path, content: &str, type_filter: Option<&TypeFilter>) -> Result<UnityFile> {
    let raw_documents = parse_raw_documents(content, type_filter)?;

    Ok(UnityFile::Asset(UnityAsset::new(
        path.to_path_buf(),
        raw_documents,
    )))
}

/// Parse raw YAML documents from file content with optional type filtering
fn parse_raw_documents(content: &str, type_filter: Option<&TypeFilter>) -> Result<Vec<RawDocument>> {
    // Split into individual YAML documents
    let raw_docs = split_yaml_documents(content)?;

    // Parse each document
    raw_docs
        .iter()
        .filter_map(|raw| parse_raw_document(raw, type_filter).transpose())
        .collect()
}

/// Parse a single raw YAML document into a RawDocument with optional type filtering
fn parse_raw_document(raw_doc: &str, type_filter: Option<&TypeFilter>) -> Result<Option<RawDocument>> {
    // Parse the Unity tag line (e.g., "--- !u!1 &12345")
    let tag = match parse_unity_tag(raw_doc) {
        Some(tag) => tag,
        None => return Ok(None), // Skip documents without Unity tags
    };

    // Extract the YAML content (everything after the tag line)
    let yaml_content = extract_yaml_content(raw_doc);

    if yaml_content.trim().is_empty() {
        return Ok(None);
    }

    // Early filtering: Extract class name without full YAML parsing
    if let Some(filter) = type_filter {
        if filter.is_filtering() {
            // Extract the class name efficiently
            let class_name = match extract_class_name(yaml_content) {
                Some(name) => name,
                None => return Ok(None), // Can't extract class name, skip
            };

            // Check if this is a MonoBehaviour
            if class_name == "MonoBehaviour" {
                // For MonoBehaviour, we need to check the m_Script GUID
                match extract_monobehaviour_guid(yaml_content) {
                    Some(guid) => {
                        if !filter.should_parse_guid(&guid) {
                            // GUID not in whitelist, skip this document
                            return Ok(None);
                        }
                    }
                    None => {
                        // Can't extract GUID, skip this MonoBehaviour
                        return Ok(None);
                    }
                }
            } else {
                // For non-MonoBehaviour, check the Unity type whitelist
                if !filter.should_parse_type(class_name) {
                    // Type not in whitelist, skip this document
                    return Ok(None);
                }
            }
        }
    }

    // If we reach here, the document passed the filter (or no filter was applied)
    // Now do the full YAML parsing
    let yaml_value: serde_yaml::Value = serde_yaml::from_str(yaml_content)?;

    // Unity documents have format "GameObject: { ... }"
    // Extract class name and inner YAML
    let (class_name, inner_yaml) = match &yaml_value {
        serde_yaml::Value::Mapping(map) if map.len() == 1 => {
            // Single-key mapping - this is the standard Unity format
            let (key, value) = map.iter().next().unwrap();
            let class_name = key
                .as_str()
                .ok_or_else(|| Error::invalid_format("Class name must be string"))?
                .to_string();
            (class_name, value.clone())
        }
        _ => {
            // Fallback for malformed documents
            let class_name = format!("UnityType{}", tag.type_id);
            (class_name, yaml_value)
        }
    };

    Ok(Some(RawDocument::new(
        tag.type_id,
        FileID::from_i64(tag.file_id),
        class_name,
        inner_yaml,
        tag.is_stripped,
    )))
}

/// Validate that the file has a proper Unity YAML header
fn validate_unity_header(content: &str, path: &Path) -> Result<()> {
    let has_yaml_header = content.starts_with("%YAML");
    let has_unity_tag = content.contains("%TAG !u! tag:unity3d.com");

    if !has_yaml_header || !has_unity_tag {
        return Err(Error::MissingHeader(path.to_path_buf()));
    }

    Ok(())
}

/// Extract the YAML content from a raw document (skip the Unity tag line)
fn extract_yaml_content(raw_doc: &str) -> &str {
    // Find the first newline after the "--- !u!" tag
    if let Some(first_line_end) = raw_doc.find('\n') {
        &raw_doc[first_line_end + 1..]
    } else {
        ""
    }
}

/// Extract the Unity class name from YAML content without full parsing
///
/// Unity documents have the format:
/// ```yaml
/// ClassName:
///   field1: value1
///   field2: value2
/// ```
///
/// This function extracts "ClassName" efficiently without parsing the entire YAML.
fn extract_class_name(yaml_content: &str) -> Option<&str> {
    // Find the first line that's not empty
    let first_line = yaml_content.lines().find(|line| !line.trim().is_empty())?;

    // Class name is the first non-whitespace text before ':'
    let class_name = first_line.trim().strip_suffix(':')?;

    Some(class_name)
}

/// Extract the m_Script GUID from a MonoBehaviour YAML document without full parsing
///
/// MonoBehaviour documents have the format:
/// ```yaml
/// MonoBehaviour:
///   m_Script: {fileID: 11500000, guid: d39ddbf1c2c3d1a4baa070e5e76548bd, type: 3}
///   ...
/// ```
///
/// Or multi-line format:
/// ```yaml
/// MonoBehaviour:
///   m_Script:
///     fileID: 11500000
///     guid: d39ddbf1c2c3d1a4baa070e5e76548bd
///     type: 3
/// ```
///
/// This function extracts the GUID value efficiently.
fn extract_monobehaviour_guid(yaml_content: &str) -> Option<Guid> {
    // Look for any line with "guid: <32 hex chars>"
    // This works for both inline and multi-line formats
    for line in yaml_content.lines() {
        if line.contains("guid:") {
            // Find "guid: " and extract the 32-character hex string after it
            if let Some(guid_start) = line.find("guid:") {
                let after_guid = &line[guid_start + 5..].trim();

                // Extract the hex string (32 characters)
                let guid_str: String = after_guid
                    .chars()
                    .take_while(|c| c.is_ascii_hexdigit())
                    .collect();

                if guid_str.len() == 32 {
                    return Guid::from_hex(&guid_str).ok();
                }
            }
        }
    }

    None
}

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

    #[test]
    fn test_validate_unity_header() {
        let valid_content = "%YAML 1.1\n%TAG !u! tag:unity3d.com,2011:\n";
        assert!(validate_unity_header(valid_content, Path::new("test.unity")).is_ok());

        let invalid_content = "Not a Unity file";
        assert!(validate_unity_header(invalid_content, Path::new("test.unity")).is_err());
    }

    #[test]
    fn test_extract_yaml_content() {
        let raw_doc = "--- !u!1 &12345\nGameObject:\n  m_Name: Test";
        let content = extract_yaml_content(raw_doc);
        assert_eq!(content, "GameObject:\n  m_Name: Test");
    }

    #[test]
    fn test_detect_file_type() {
        assert!(matches!(
            detect_file_type(Path::new("test.unity")),
            FileType::Scene
        ));
        assert!(matches!(
            detect_file_type(Path::new("test.prefab")),
            FileType::Prefab
        ));
        assert!(matches!(
            detect_file_type(Path::new("test.asset")),
            FileType::Asset
        ));
        assert!(matches!(
            detect_file_type(Path::new("test.txt")),
            FileType::Unknown
        ));
    }

    #[test]
    fn test_parse_unity_file_filtered_accepts_matching_path() {
        use regex::Regex;

        let filter = Regex::new(r"Test").unwrap();
        let path = Path::new("TestScene.unity");

        // Should match and attempt to parse (will fail because file doesn't exist)
        let result = parse_unity_file_filtered(path, Some(&filter), None);
        assert!(result.is_err());

        // Error should be IO error (file not found), not filter error
        match result {
            Err(e) => {
                let err_msg = e.to_string();
                assert!(
                    !err_msg.contains("does not match filter"),
                    "Should not be a filter error, got: {}",
                    err_msg
                );
            }
            Ok(_) => panic!("Expected error for non-existent file"),
        }
    }

    #[test]
    fn test_parse_unity_file_filtered_rejects_non_matching_path() {
        use regex::Regex;

        let filter = Regex::new(r"Test").unwrap();
        let path = Path::new("MainScene.unity");

        // Should reject due to filter
        let result = parse_unity_file_filtered(path, Some(&filter), None);
        assert!(result.is_err());

        // Error should be filter error
        match result {
            Err(e) => {
                let err_msg = e.to_string();
                assert!(
                    err_msg.contains("does not match filter"),
                    "Expected filter error, got: {}",
                    err_msg
                );
            }
            Ok(_) => panic!("Expected filter error"),
        }
    }

    #[test]
    fn test_parse_unity_file_filtered_none_accepts_all() {
        let path = Path::new("AnyScene.unity");

        // No filter should accept any path (will fail with IO error)
        let result = parse_unity_file_filtered(path, None, None);
        assert!(result.is_err());

        // Should be IO error, not filter error
        match result {
            Err(e) => {
                let err_msg = e.to_string();
                assert!(
                    !err_msg.contains("does not match filter"),
                    "Should not be a filter error with None filter, got: {}",
                    err_msg
                );
            }
            Ok(_) => panic!("Expected IO error for non-existent file"),
        }
    }

    #[test]
    fn test_parse_unity_file_uses_default_filter() {
        let path = Path::new("AnyScene.unity");

        // parse_unity_file should work the same as filtered with None
        let result1 = parse_unity_file(path);
        let result2 = parse_unity_file_filtered(path, None, None);

        // Both should have the same error (IO error for missing file)
        assert!(result1.is_err());
        assert!(result2.is_err());
    }

    #[test]
    fn test_extract_class_name() {
        let yaml = "GameObject:\n  m_Name: Test";
        assert_eq!(extract_class_name(yaml), Some("GameObject"));

        let yaml2 = "Transform:\n  m_LocalPosition: {x: 1, y: 2, z: 3}";
        assert_eq!(extract_class_name(yaml2), Some("Transform"));

        let yaml3 = "MonoBehaviour:\n  m_Script: {fileID: 11500000}";
        assert_eq!(extract_class_name(yaml3), Some("MonoBehaviour"));

        let empty = "";
        assert_eq!(extract_class_name(empty), None);
    }

    #[test]
    fn test_extract_monobehaviour_guid() {
        let yaml = "MonoBehaviour:\n  m_Script: {fileID: 11500000, guid: d39ddbf1c2c3d1a4baa070e5e76548bd, type: 3}";
        let guid = extract_monobehaviour_guid(yaml);
        assert!(guid.is_some());
        assert_eq!(
            guid.unwrap().to_hex(),
            "d39ddbf1c2c3d1a4baa070e5e76548bd"
        );

        // Multi-line format
        let yaml2 = "MonoBehaviour:\n  m_Script:\n    fileID: 11500000\n    guid: abc123def456789012345678901234ab\n    type: 3";
        let guid2 = extract_monobehaviour_guid(yaml2);
        assert!(guid2.is_some());
        assert_eq!(
            guid2.unwrap().to_hex(),
            "abc123def456789012345678901234ab"
        );

        let no_guid = "MonoBehaviour:\n  m_Name: Test";
        assert_eq!(extract_monobehaviour_guid(no_guid), None);
    }

    #[test]
    fn test_type_filter_document_parse_all() {
        let filter = TypeFilter::parse_all();
        assert!(filter.should_parse_type("Transform"));
        assert!(filter.should_parse_type("GameObject"));
        assert!(filter.should_parse_type("AnyType"));
        assert!(!filter.is_filtering());
    }

    #[test]
    fn test_type_filter_document_with_unity_types() {
        use std::collections::HashSet;

        let mut types = HashSet::new();
        types.insert("Transform".to_string());
        types.insert("GameObject".to_string());

        let filter = TypeFilter::with_unity_types(types);

        assert!(filter.should_parse_type("Transform"));
        assert!(filter.should_parse_type("GameObject"));
        assert!(!filter.should_parse_type("RectTransform"));
        assert!(filter.is_filtering());

        // Should still accept any MonoBehaviour GUID since we didn't set a GUID filter
        let guid = Guid::from_hex("d39ddbf1c2c3d1a4baa070e5e76548bd").unwrap();
        assert!(filter.should_parse_guid(&guid));
    }

    #[test]
    fn test_type_filter_document_with_monobehaviour_guids() {
        use std::collections::HashSet;

        let mut guids = HashSet::new();
        let guid1 = Guid::from_hex("d39ddbf1c2c3d1a4baa070e5e76548bd").unwrap();
        let guid2 = Guid::from_hex("abc123def456789012345678901234ab").unwrap();
        guids.insert(guid1);
        guids.insert(guid2);

        let filter = TypeFilter::with_monobehaviour_guids(guids);

        assert!(filter.should_parse_guid(&guid1));
        assert!(filter.should_parse_guid(&guid2));

        let guid3 = Guid::from_hex("00000000000000000000000000000000").unwrap();
        assert!(!filter.should_parse_guid(&guid3));

        assert!(filter.is_filtering());

        // Should still accept any Unity type since we didn't set a type filter
        assert!(filter.should_parse_type("Transform"));
        assert!(filter.should_parse_type("AnyType"));
    }

    #[test]
    fn test_type_filter_document_with_both() {
        use std::collections::HashSet;

        let mut types = HashSet::new();
        types.insert("Transform".to_string());

        let mut guids = HashSet::new();
        let guid1 = Guid::from_hex("d39ddbf1c2c3d1a4baa070e5e76548bd").unwrap();
        guids.insert(guid1);

        let filter = TypeFilter::with_both(types, guids);

        // Only Transform should pass
        assert!(filter.should_parse_type("Transform"));
        assert!(!filter.should_parse_type("GameObject"));

        // Only guid1 should pass
        assert!(filter.should_parse_guid(&guid1));
        let guid2 = Guid::from_hex("abc123def456789012345678901234ab").unwrap();
        assert!(!filter.should_parse_guid(&guid2));

        assert!(filter.is_filtering());
    }
}