use std::path::Path;

use compliance_core::error::CoreError;
use compliance_core::models::graph::{CodeEdge, CodeEdgeKind, CodeNode, CodeNodeKind};
use compliance_core::traits::graph_builder::{LanguageParser, ParseOutput};
use tree_sitter::{Node, Parser};

pub struct RustParser;

impl Default for RustParser {
    fn default() -> Self {
        Self::new()
    }
}

impl RustParser {
    pub fn new() -> Self {
        Self
    }

    fn walk_tree(
        &self,
        node: Node<'_>,
        source: &str,
        file_path: &str,
        repo_id: &str,
        graph_build_id: &str,
        parent_qualified: Option<&str>,
        output: &mut ParseOutput,
    ) {
        match node.kind() {
            "function_item" | "function_signature_item" => {
                if let Some(name_node) = node.child_by_field_name("name") {
                    let name = &source[name_node.byte_range()];
                    let qualified = match parent_qualified {
                        Some(p) => format!("{p}::{name}"),
                        None => format!("{file_path}::{name}"),
                    };

                    let is_entry = name == "main"
                        || self.has_attribute(&node, source, "test")
                        || self.has_attribute(&node, source, "tokio::main")
                        || self.has_pub_visibility(&node, source);

                    output.nodes.push(CodeNode {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        qualified_name: qualified.clone(),
                        name: name.to_string(),
                        kind: CodeNodeKind::Function,
                        file_path: file_path.to_string(),
                        start_line: node.start_position().row as u32 + 1,
                        end_line: node.end_position().row as u32 + 1,
                        language: "rust".to_string(),
                        community_id: None,
                        is_entry_point: is_entry,
                        graph_index: None,
                    });

                    // Extract function calls within the body
                    if let Some(body) = node.child_by_field_name("body") {
                        self.extract_calls(
                            body,
                            source,
                            file_path,
                            repo_id,
                            graph_build_id,
                            &qualified,
                            output,
                        );
                    }
                }
            }
            "struct_item" => {
                if let Some(name_node) = node.child_by_field_name("name") {
                    let name = &source[name_node.byte_range()];
                    let qualified = match parent_qualified {
                        Some(p) => format!("{p}::{name}"),
                        None => format!("{file_path}::{name}"),
                    };

                    output.nodes.push(CodeNode {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        qualified_name: qualified,
                        name: name.to_string(),
                        kind: CodeNodeKind::Struct,
                        file_path: file_path.to_string(),
                        start_line: node.start_position().row as u32 + 1,
                        end_line: node.end_position().row as u32 + 1,
                        language: "rust".to_string(),
                        community_id: None,
                        is_entry_point: false,
                        graph_index: None,
                    });
                }
            }
            "enum_item" => {
                if let Some(name_node) = node.child_by_field_name("name") {
                    let name = &source[name_node.byte_range()];
                    let qualified = match parent_qualified {
                        Some(p) => format!("{p}::{name}"),
                        None => format!("{file_path}::{name}"),
                    };

                    output.nodes.push(CodeNode {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        qualified_name: qualified,
                        name: name.to_string(),
                        kind: CodeNodeKind::Enum,
                        file_path: file_path.to_string(),
                        start_line: node.start_position().row as u32 + 1,
                        end_line: node.end_position().row as u32 + 1,
                        language: "rust".to_string(),
                        community_id: None,
                        is_entry_point: false,
                        graph_index: None,
                    });
                }
            }
            "trait_item" => {
                if let Some(name_node) = node.child_by_field_name("name") {
                    let name = &source[name_node.byte_range()];
                    let qualified = match parent_qualified {
                        Some(p) => format!("{p}::{name}"),
                        None => format!("{file_path}::{name}"),
                    };

                    output.nodes.push(CodeNode {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        qualified_name: qualified.clone(),
                        name: name.to_string(),
                        kind: CodeNodeKind::Trait,
                        file_path: file_path.to_string(),
                        start_line: node.start_position().row as u32 + 1,
                        end_line: node.end_position().row as u32 + 1,
                        language: "rust".to_string(),
                        community_id: None,
                        is_entry_point: false,
                        graph_index: None,
                    });

                    // Parse methods inside the trait
                    self.walk_children(
                        node,
                        source,
                        file_path,
                        repo_id,
                        graph_build_id,
                        Some(&qualified),
                        output,
                    );
                    return; // Don't walk children again
                }
            }
            "impl_item" => {
                // Extract impl target type for qualified naming
                let impl_name = self.extract_impl_type(&node, source);
                let qualified = match parent_qualified {
                    Some(p) => format!("{p}::{impl_name}"),
                    None => format!("{file_path}::{impl_name}"),
                };

                // Check for trait impl (impl Trait for Type)
                if let Some(trait_node) = node.child_by_field_name("trait") {
                    let trait_name = &source[trait_node.byte_range()];
                    output.edges.push(CodeEdge {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        source: qualified.clone(),
                        target: trait_name.to_string(),
                        kind: CodeEdgeKind::Implements,
                        file_path: file_path.to_string(),
                        line_number: Some(node.start_position().row as u32 + 1),
                    });
                }

                // Walk methods inside impl block
                self.walk_children(
                    node,
                    source,
                    file_path,
                    repo_id,
                    graph_build_id,
                    Some(&qualified),
                    output,
                );
                return;
            }
            "use_declaration" => {
                let use_text = &source[node.byte_range()];
                // Extract the imported path
                if let Some(path) = self.extract_use_path(use_text) {
                    output.edges.push(CodeEdge {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        source: parent_qualified.unwrap_or(file_path).to_string(),
                        target: path,
                        kind: CodeEdgeKind::Imports,
                        file_path: file_path.to_string(),
                        line_number: Some(node.start_position().row as u32 + 1),
                    });
                }
            }
            "mod_item" => {
                if let Some(name_node) = node.child_by_field_name("name") {
                    let name = &source[name_node.byte_range()];
                    let qualified = match parent_qualified {
                        Some(p) => format!("{p}::{name}"),
                        None => format!("{file_path}::{name}"),
                    };

                    output.nodes.push(CodeNode {
                        id: None,
                        repo_id: repo_id.to_string(),
                        graph_build_id: graph_build_id.to_string(),
                        qualified_name: qualified.clone(),
                        name: name.to_string(),
                        kind: CodeNodeKind::Module,
                        file_path: file_path.to_string(),
                        start_line: node.start_position().row as u32 + 1,
                        end_line: node.end_position().row as u32 + 1,
                        language: "rust".to_string(),
                        community_id: None,
                        is_entry_point: false,
                        graph_index: None,
                    });

                    // If it has a body (inline module), walk it
                    if let Some(body) = node.child_by_field_name("body") {
                        self.walk_children(
                            body,
                            source,
                            file_path,
                            repo_id,
                            graph_build_id,
                            Some(&qualified),
                            output,
                        );
                        return;
                    }
                }
            }
            _ => {}
        }

        // Default: walk children
        self.walk_children(
            node,
            source,
            file_path,
            repo_id,
            graph_build_id,
            parent_qualified,
            output,
        );
    }

    fn walk_children(
        &self,
        node: Node<'_>,
        source: &str,
        file_path: &str,
        repo_id: &str,
        graph_build_id: &str,
        parent_qualified: Option<&str>,
        output: &mut ParseOutput,
    ) {
        let mut cursor = node.walk();
        for child in node.children(&mut cursor) {
            self.walk_tree(
                child,
                source,
                file_path,
                repo_id,
                graph_build_id,
                parent_qualified,
                output,
            );
        }
    }

    fn extract_calls(
        &self,
        node: Node<'_>,
        source: &str,
        file_path: &str,
        repo_id: &str,
        graph_build_id: &str,
        caller_qualified: &str,
        output: &mut ParseOutput,
    ) {
        if node.kind() == "call_expression" {
            if let Some(func_node) = node.child_by_field_name("function") {
                let callee = &source[func_node.byte_range()];
                output.edges.push(CodeEdge {
                    id: None,
                    repo_id: repo_id.to_string(),
                    graph_build_id: graph_build_id.to_string(),
                    source: caller_qualified.to_string(),
                    target: callee.to_string(),
                    kind: CodeEdgeKind::Calls,
                    file_path: file_path.to_string(),
                    line_number: Some(node.start_position().row as u32 + 1),
                });
            }
        }

        let mut cursor = node.walk();
        for child in node.children(&mut cursor) {
            self.extract_calls(
                child,
                source,
                file_path,
                repo_id,
                graph_build_id,
                caller_qualified,
                output,
            );
        }
    }

    fn has_attribute(&self, node: &Node<'_>, source: &str, attr_name: &str) -> bool {
        if let Some(prev) = node.prev_sibling() {
            if prev.kind() == "attribute_item" || prev.kind() == "attribute" {
                let text = &source[prev.byte_range()];
                return text.contains(attr_name);
            }
        }
        false
    }

    fn has_pub_visibility(&self, node: &Node<'_>, source: &str) -> bool {
        let mut cursor = node.walk();
        for child in node.children(&mut cursor) {
            if child.kind() == "visibility_modifier" {
                let text = &source[child.byte_range()];
                return text == "pub";
            }
        }
        false
    }

    fn extract_impl_type(&self, node: &Node<'_>, source: &str) -> String {
        if let Some(type_node) = node.child_by_field_name("type") {
            return source[type_node.byte_range()].to_string();
        }
        "unknown".to_string()
    }

    fn extract_use_path(&self, use_text: &str) -> Option<String> {
        // "use foo::bar::baz;" -> "foo::bar::baz"
        let trimmed = use_text.strip_prefix("use ")?.trim_end_matches(';').trim();
        Some(trimmed.to_string())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use compliance_core::traits::graph_builder::LanguageParser;
    use std::path::PathBuf;

    fn parse_rust(source: &str) -> ParseOutput {
        let parser = RustParser::new();
        parser
            .parse_file(&PathBuf::from("test.rs"), source, "repo1", "build1")
            .unwrap()
    }

    #[test]
    fn test_extract_use_path_simple() {
        let parser = RustParser::new();
        assert_eq!(
            parser.extract_use_path("use std::collections::HashMap;"),
            Some("std::collections::HashMap".to_string())
        );
    }

    #[test]
    fn test_extract_use_path_nested() {
        let parser = RustParser::new();
        assert_eq!(
            parser.extract_use_path("use crate::models::graph::CodeNode;"),
            Some("crate::models::graph::CodeNode".to_string())
        );
    }

    #[test]
    fn test_extract_use_path_no_prefix() {
        let parser = RustParser::new();
        assert_eq!(parser.extract_use_path("let x = 5;"), None);
    }

    #[test]
    fn test_extract_use_path_empty() {
        let parser = RustParser::new();
        assert_eq!(parser.extract_use_path(""), None);
    }

    #[test]
    fn test_parse_function() {
        let output = parse_rust("fn hello() {\n    let x = 1;\n}\n");
        let fn_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Function)
            .collect();
        assert_eq!(fn_nodes.len(), 1);
        assert_eq!(fn_nodes[0].name, "hello");
        assert!(fn_nodes[0].qualified_name.contains("hello"));
    }

    #[test]
    fn test_parse_struct() {
        let output = parse_rust("struct Foo {\n    x: i32,\n}\n");
        let struct_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Struct)
            .collect();
        assert_eq!(struct_nodes.len(), 1);
        assert_eq!(struct_nodes[0].name, "Foo");
    }

    #[test]
    fn test_parse_enum() {
        let output = parse_rust("enum Color {\n    Red,\n    Blue,\n}\n");
        let enum_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Enum)
            .collect();
        assert_eq!(enum_nodes.len(), 1);
        assert_eq!(enum_nodes[0].name, "Color");
    }

    #[test]
    fn test_parse_trait() {
        let output = parse_rust("trait Drawable {\n    fn draw(&self);\n}\n");
        let trait_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Trait)
            .collect();
        assert_eq!(trait_nodes.len(), 1);
        assert_eq!(trait_nodes[0].name, "Drawable");
    }

    #[test]
    fn test_parse_file_node_always_created() {
        let output = parse_rust("");
        let file_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::File)
            .collect();
        assert_eq!(file_nodes.len(), 1);
        assert_eq!(file_nodes[0].language, "rust");
    }

    #[test]
    fn test_parse_multiple_functions() {
        let source = "fn foo() {}\nfn bar() {}\nfn baz() {}\n";
        let output = parse_rust(source);
        let fn_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Function)
            .collect();
        assert_eq!(fn_nodes.len(), 3);
    }

    #[test]
    fn test_parse_main_is_entry_point() {
        let output = parse_rust("fn main() {\n    println!(\"hi\");\n}\n");
        let main_node = output.nodes.iter().find(|n| n.name == "main").unwrap();
        assert!(main_node.is_entry_point);
    }

    #[test]
    fn test_parse_pub_fn_is_entry_point() {
        let output = parse_rust("pub fn handler() {}\n");
        let node = output.nodes.iter().find(|n| n.name == "handler").unwrap();
        assert!(node.is_entry_point);
    }

    #[test]
    fn test_parse_private_fn_is_not_entry_point() {
        let output = parse_rust("fn helper() {}\n");
        let node = output.nodes.iter().find(|n| n.name == "helper").unwrap();
        assert!(!node.is_entry_point);
    }

    #[test]
    fn test_parse_function_calls_create_edges() {
        let source = "fn caller() {\n    callee();\n}\nfn callee() {}\n";
        let output = parse_rust(source);
        let call_edges: Vec<_> = output
            .edges
            .iter()
            .filter(|e| e.kind == CodeEdgeKind::Calls)
            .collect();
        assert!(!call_edges.is_empty());
        assert!(call_edges.iter().any(|e| e.target.contains("callee")));
    }

    #[test]
    fn test_parse_use_declaration_creates_import_edge() {
        let source = "use std::collections::HashMap;\nfn foo() {}\n";
        let output = parse_rust(source);
        let import_edges: Vec<_> = output
            .edges
            .iter()
            .filter(|e| e.kind == CodeEdgeKind::Imports)
            .collect();
        assert!(!import_edges.is_empty());
    }

    #[test]
    fn test_parse_impl_methods() {
        let source = "struct Foo {}\nimpl Foo {\n    fn do_thing(&self) {}\n}\n";
        let output = parse_rust(source);
        let fn_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Function)
            .collect();
        assert_eq!(fn_nodes.len(), 1);
        assert_eq!(fn_nodes[0].name, "do_thing");
        // Method should be qualified under the impl type
        assert!(fn_nodes[0].qualified_name.contains("Foo"));
    }

    #[test]
    fn test_parse_mod_item() {
        let source = "mod inner {\n    fn nested() {}\n}\n";
        let output = parse_rust(source);
        let mod_nodes: Vec<_> = output
            .nodes
            .iter()
            .filter(|n| n.kind == CodeNodeKind::Module)
            .collect();
        assert_eq!(mod_nodes.len(), 1);
        assert_eq!(mod_nodes[0].name, "inner");
    }

    #[test]
    fn test_parse_line_numbers() {
        let source = "fn first() {}\n\n\nfn second() {}\n";
        let output = parse_rust(source);
        let first = output.nodes.iter().find(|n| n.name == "first").unwrap();
        let second = output.nodes.iter().find(|n| n.name == "second").unwrap();
        assert_eq!(first.start_line, 1);
        assert!(second.start_line > first.start_line);
    }

    #[test]
    fn test_language_and_extensions() {
        let parser = RustParser::new();
        assert_eq!(parser.language(), "rust");
        assert_eq!(parser.extensions(), &["rs"]);
    }
}

impl LanguageParser for RustParser {
    fn language(&self) -> &str {
        "rust"
    }

    fn extensions(&self) -> &[&str] {
        &["rs"]
    }

    fn parse_file(
        &self,
        file_path: &Path,
        source: &str,
        repo_id: &str,
        graph_build_id: &str,
    ) -> Result<ParseOutput, CoreError> {
        let mut parser = Parser::new();
        let language = tree_sitter_rust::LANGUAGE;
        parser
            .set_language(&language.into())
            .map_err(|e| CoreError::Graph(format!("Failed to set Rust language: {e}")))?;

        let tree = parser
            .parse(source, None)
            .ok_or_else(|| CoreError::Graph("Failed to parse Rust file".to_string()))?;

        let file_path_str = file_path.to_string_lossy().to_string();
        let mut output = ParseOutput::default();

        // Add file node
        output.nodes.push(CodeNode {
            id: None,
            repo_id: repo_id.to_string(),
            graph_build_id: graph_build_id.to_string(),
            qualified_name: file_path_str.clone(),
            name: file_path
                .file_name()
                .map(|n| n.to_string_lossy().to_string())
                .unwrap_or_default(),
            kind: CodeNodeKind::File,
            file_path: file_path_str.clone(),
            start_line: 1,
            end_line: source.lines().count() as u32,
            language: "rust".to_string(),
            community_id: None,
            is_entry_point: false,
            graph_index: None,
        });

        self.walk_tree(
            tree.root_node(),
            source,
            &file_path_str,
            repo_id,
            graph_build_id,
            None,
            &mut output,
        );

        Ok(output)
    }
}