use rhai::{ Dynamic, Engine, EvalAltResult};
use crate::services::keywords::create_draft::{create_draft_keyword};
use crate::services::keywords::create_site::create_site_keyword;
use crate::services::keywords::find::{find_keyword};
use crate::services::keywords::for_next::for_keyword;
use crate::services::keywords::get::get_keyword;
use crate::services::keywords::get_website::get_website_keyword;
use crate::services::keywords::print::print_keyword;
use crate::services::keywords::set::set_keyword;
use crate::services::keywords::wait::wait_keyword;
use crate::services::state::AppState;

pub struct ScriptService {
    engine: Engine,
}

impl ScriptService {
    pub fn new(state: &AppState) -> Self {
        let mut engine = Engine::new();
       
        // Configure engine for BASIC-like syntax
        engine.set_allow_anonymous_fn(true);
        engine.set_allow_looping(true);
        
        create_draft_keyword(state, &mut engine);
        create_site_keyword(state, &mut engine);
        find_keyword(state, &mut engine);
        for_keyword(state, &mut engine);     
        get_keyword(state, &mut engine);
        get_website_keyword(state, &mut engine);
        set_keyword(state, &mut engine);
        wait_keyword(state, &mut engine);
        print_keyword(state, &mut engine);
        ScriptService { engine }
    }

    fn preprocess_basic_script(&self, script: &str) -> String {
        let mut result = String::new();
        let mut for_stack: Vec<usize> = Vec::new();
        let mut current_indent = 0;

        for line in script.lines() {
            let trimmed = line.trim();

            // Skip empty lines and comments
            if trimmed.is_empty() || trimmed.starts_with("//") || trimmed.starts_with("REM") {
                result.push_str(line);
                result.push('\n');
                continue;
            }

            // Handle FOR EACH start
            if trimmed.starts_with("FOR EACH") {
                for_stack.push(current_indent);
                result.push_str(&" ".repeat(current_indent));
                result.push_str(trimmed);
                result.push_str("{\n");
                current_indent += 4;
                result.push_str(&" ".repeat(current_indent));
                result.push('\n');
                continue;
            }

            // Handle NEXT
            if trimmed.starts_with("NEXT") {
                if let Some(expected_indent) = for_stack.pop() {
                    if (current_indent - 4) != expected_indent {
                        panic!("NEXT without matching FOR EACH");
                    }
                    current_indent = current_indent - 4;
                    result.push_str(&" ".repeat(current_indent));
                    result.push_str("}\n");
                    result.push_str(&" ".repeat(current_indent));
                    result.push_str(trimmed);
                    result.push(';');
                    result.push('\n');
                    continue;
                } else {
                    panic!("NEXT without matching FOR EACH");
                }
            }

            // Handle EXIT FOR
            if trimmed == "EXIT FOR" {
                result.push_str(&" ".repeat(current_indent));
                result.push_str(trimmed);
                result.push('\n');
                continue;
            }

            // Handle regular lines - no semicolons added for BASIC-style commands
            result.push_str(&" ".repeat(current_indent));

            let basic_commands = [
                "SET", "CREATE", "PRINT", "FOR", "FIND", "GET", "EXIT", "IF", "THEN", "ELSE",
                "END IF", "WHILE", "WEND", "DO", "LOOP",
            ];

            let is_basic_command = basic_commands.iter().any(|&cmd| trimmed.starts_with(cmd));
            let is_control_flow = trimmed.starts_with("IF")
                || trimmed.starts_with("ELSE")
                || trimmed.starts_with("END IF");

            if is_basic_command || !for_stack.is_empty() || is_control_flow {
                // Don'ta add semicolons for BASIC-style commands or inside blocks
                result.push_str(trimmed);
                result.push(';');
            } else {
                // Add semicolons only for BASIC statements
                result.push_str(trimmed);
                if !trimmed.ends_with(';') && !trimmed.ends_with('{') && !trimmed.ends_with('}') {
                    result.push(';');
                }
            }
            result.push('\n');
        }

        if !for_stack.is_empty() {
            panic!("Unclosed FOR EACH loop");
        }

        result
    }

    /// Preprocesses BASIC-style script to handle semicolon-free syntax
    pub fn compile(&self, script: &str) -> Result<rhai::AST, Box<EvalAltResult>> {
        let processed_script = self.preprocess_basic_script(script);
        match self.engine.compile(&processed_script) {
            Ok(ast) => Ok(ast),
            Err(parse_error) => Err(Box::new(EvalAltResult::from(parse_error))),
        }
    }

    pub fn run(&self, ast: &rhai::AST) -> Result<Dynamic, Box<EvalAltResult>> {
        self.engine.eval_ast(ast)
    }
}