use compliance_core::error::CoreError;
use compliance_core::models::graph::CodeNode;
use tantivy::collector::TopDocs;
use tantivy::query::QueryParser;
use tantivy::schema::{Schema, Value, STORED, TEXT};
use tantivy::{doc, Index, IndexWriter, ReloadPolicy};
use tracing::info;

/// BM25 text search index over code symbols
pub struct SymbolIndex {
    index: Index,
    #[allow(dead_code)]
    schema: Schema,
    qualified_name_field: tantivy::schema::Field,
    name_field: tantivy::schema::Field,
    kind_field: tantivy::schema::Field,
    file_path_field: tantivy::schema::Field,
    language_field: tantivy::schema::Field,
}

#[derive(Debug, Clone, serde::Serialize)]
pub struct SearchResult {
    pub qualified_name: String,
    pub name: String,
    pub kind: String,
    pub file_path: String,
    pub language: String,
    pub score: f32,
}

impl SymbolIndex {
    /// Create a new in-memory symbol index
    pub fn new() -> Result<Self, CoreError> {
        let mut schema_builder = Schema::builder();
        let qualified_name_field = schema_builder.add_text_field("qualified_name", TEXT | STORED);
        let name_field = schema_builder.add_text_field("name", TEXT | STORED);
        let kind_field = schema_builder.add_text_field("kind", TEXT | STORED);
        let file_path_field = schema_builder.add_text_field("file_path", TEXT | STORED);
        let language_field = schema_builder.add_text_field("language", TEXT | STORED);
        let schema = schema_builder.build();

        let index = Index::create_in_ram(schema.clone());

        Ok(Self {
            index,
            schema,
            qualified_name_field,
            name_field,
            kind_field,
            file_path_field,
            language_field,
        })
    }

    /// Index a set of code nodes
    pub fn index_nodes(&self, nodes: &[CodeNode]) -> Result<(), CoreError> {
        let mut writer: IndexWriter = self
            .index
            .writer(50_000_000)
            .map_err(|e| CoreError::Graph(format!("Failed to create index writer: {e}")))?;

        for node in nodes {
            writer
                .add_document(doc!(
                    self.qualified_name_field => node.qualified_name.as_str(),
                    self.name_field => node.name.as_str(),
                    self.kind_field => node.kind.to_string(),
                    self.file_path_field => node.file_path.as_str(),
                    self.language_field => node.language.as_str(),
                ))
                .map_err(|e| CoreError::Graph(format!("Failed to add document: {e}")))?;
        }

        writer
            .commit()
            .map_err(|e| CoreError::Graph(format!("Failed to commit index: {e}")))?;

        info!(nodes = nodes.len(), "Symbol index built");
        Ok(())
    }

    /// Search for symbols matching a query
    pub fn search(&self, query_str: &str, limit: usize) -> Result<Vec<SearchResult>, CoreError> {
        let reader = self
            .index
            .reader_builder()
            .reload_policy(ReloadPolicy::Manual)
            .try_into()
            .map_err(|e| CoreError::Graph(format!("Failed to create reader: {e}")))?;

        let searcher = reader.searcher();
        let query_parser = QueryParser::for_index(
            &self.index,
            vec![self.name_field, self.qualified_name_field],
        );

        let query = query_parser
            .parse_query(query_str)
            .map_err(|e| CoreError::Graph(format!("Failed to parse query: {e}")))?;

        let top_docs = searcher
            .search(&query, &TopDocs::with_limit(limit))
            .map_err(|e| CoreError::Graph(format!("Search failed: {e}")))?;

        let mut results = Vec::new();
        for (score, doc_address) in top_docs {
            let doc: tantivy::TantivyDocument = searcher
                .doc(doc_address)
                .map_err(|e| CoreError::Graph(format!("Failed to retrieve doc: {e}")))?;

            let get_field = |field: tantivy::schema::Field| -> String {
                doc.get_first(field)
                    .and_then(|v| v.as_str())
                    .unwrap_or("")
                    .to_string()
            };

            results.push(SearchResult {
                qualified_name: get_field(self.qualified_name_field),
                name: get_field(self.name_field),
                kind: get_field(self.kind_field),
                file_path: get_field(self.file_path_field),
                language: get_field(self.language_field),
                score,
            });
        }

        Ok(results)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use compliance_core::models::graph::CodeNodeKind;

    fn make_node(
        qualified_name: &str,
        name: &str,
        kind: CodeNodeKind,
        file_path: &str,
        language: &str,
    ) -> CodeNode {
        CodeNode {
            id: None,
            repo_id: "test".to_string(),
            graph_build_id: "build1".to_string(),
            qualified_name: qualified_name.to_string(),
            name: name.to_string(),
            kind,
            file_path: file_path.to_string(),
            start_line: 1,
            end_line: 10,
            language: language.to_string(),
            community_id: None,
            is_entry_point: false,
            graph_index: None,
        }
    }

    #[test]
    fn test_new_creates_index() {
        let index = SymbolIndex::new();
        assert!(index.is_ok());
    }

    #[test]
    fn test_index_empty_nodes() {
        let index = SymbolIndex::new().unwrap();
        let result = index.index_nodes(&[]);
        assert!(result.is_ok());
    }

    #[test]
    fn test_index_and_search_single_node() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![make_node(
            "src/main.rs::main",
            "main",
            CodeNodeKind::Function,
            "src/main.rs",
            "rust",
        )];
        index.index_nodes(&nodes).unwrap();

        let results = index.search("main", 10).unwrap();
        assert!(!results.is_empty());
        assert_eq!(results[0].name, "main");
        assert_eq!(results[0].qualified_name, "src/main.rs::main");
    }

    #[test]
    fn test_search_no_results() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![make_node(
            "src/main.rs::foo",
            "foo",
            CodeNodeKind::Function,
            "src/main.rs",
            "rust",
        )];
        index.index_nodes(&nodes).unwrap();

        let results = index.search("zzzznonexistent", 10).unwrap();
        assert!(results.is_empty());
    }

    #[test]
    fn test_search_multiple_nodes() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![
            make_node(
                "a.rs::handle_request",
                "handle_request",
                CodeNodeKind::Function,
                "a.rs",
                "rust",
            ),
            make_node(
                "b.rs::handle_response",
                "handle_response",
                CodeNodeKind::Function,
                "b.rs",
                "rust",
            ),
            make_node(
                "c.rs::process_data",
                "process_data",
                CodeNodeKind::Function,
                "c.rs",
                "rust",
            ),
        ];
        index.index_nodes(&nodes).unwrap();

        let results = index.search("handle", 10).unwrap();
        assert!(results.len() >= 2);
    }

    #[test]
    fn test_search_limit() {
        let index = SymbolIndex::new().unwrap();
        let mut nodes = Vec::new();
        for i in 0..20 {
            nodes.push(make_node(
                &format!("mod::func_{i}"),
                &format!("func_{i}"),
                CodeNodeKind::Function,
                "mod.rs",
                "rust",
            ));
        }
        index.index_nodes(&nodes).unwrap();

        let results = index.search("func", 5).unwrap();
        assert!(results.len() <= 5);
    }

    #[test]
    fn test_search_result_has_score() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![make_node(
            "src/lib.rs::compute",
            "compute",
            CodeNodeKind::Function,
            "src/lib.rs",
            "rust",
        )];
        index.index_nodes(&nodes).unwrap();

        let results = index.search("compute", 10).unwrap();
        assert!(!results.is_empty());
        assert!(results[0].score > 0.0);
    }

    #[test]
    fn test_search_result_fields() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![make_node(
            "src/app.py::MyClass",
            "MyClass",
            CodeNodeKind::Class,
            "src/app.py",
            "python",
        )];
        index.index_nodes(&nodes).unwrap();

        let results = index.search("MyClass", 10).unwrap();
        assert_eq!(results.len(), 1);
        assert_eq!(results[0].name, "MyClass");
        assert_eq!(results[0].kind, "class");
        assert_eq!(results[0].file_path, "src/app.py");
        assert_eq!(results[0].language, "python");
    }

    #[test]
    fn test_search_empty_query() {
        let index = SymbolIndex::new().unwrap();
        let nodes = vec![make_node(
            "src/lib.rs::foo",
            "foo",
            CodeNodeKind::Function,
            "src/lib.rs",
            "rust",
        )];
        index.index_nodes(&nodes).unwrap();

        // Empty query may parse error or return empty - both acceptable
        let result = index.search("", 10);
        // Just verify it doesn't panic
        let _ = result;
    }
}