use colored::*;

use crate::{
    directive_actions::DirectiveAction, language::ProgrammingLanguageInterface, InterpreterDirectiveOutput,
    Repl,
};

/// A CommandTree is either a `Terminal` or a `NonTerminal`. When command parsing reaches the first
/// Terminal, it will use the `DirectiveAction` found there to find an appropriate function to execute,
/// and then execute it with any remaining arguments
#[derive(Clone)]
pub enum CommandTree {
    Terminal {
        name: String,
        children: Vec<CommandTree>,
        help_msg: Option<String>,
        action: DirectiveAction,
    },
    NonTerminal {
        name: String,
        children: Vec<CommandTree>,
        help_msg: Option<String>,
        action: DirectiveAction,
    },
    Top(Vec<CommandTree>),
}

impl CommandTree {
    pub fn nonterm_no_further_tab_completions(s: &str, help: Option<&str>) -> CommandTree {
        CommandTree::NonTerminal {
            name: s.to_string(),
            help_msg: help.map(|x| x.to_string()),
            children: vec![],
            action: DirectiveAction::Null,
        }
    }

    pub fn terminal(
        s: &str,
        help: Option<&str>,
        children: Vec<CommandTree>,
        action: DirectiveAction,
    ) -> CommandTree {
        CommandTree::Terminal { name: s.to_string(), help_msg: help.map(|x| x.to_string()), children, action }
    }

    pub fn nonterm(s: &str, help: Option<&str>, children: Vec<CommandTree>) -> CommandTree {
        CommandTree::NonTerminal {
            name: s.to_string(),
            help_msg: help.map(|x| x.to_string()),
            children,
            action: DirectiveAction::Null,
        }
    }

    pub fn get_cmd(&self) -> &str {
        match self {
            CommandTree::Terminal { name, .. } => name.as_str(),
            CommandTree::NonTerminal { name, .. } => name.as_str(),
            CommandTree::Top(_) => "",
        }
    }
    pub fn get_help(&self) -> &str {
        match self {
            CommandTree::Terminal { help_msg, .. } =>
                help_msg.as_ref().map(|s| s.as_str()).unwrap_or("<no help text provided>"),
            CommandTree::NonTerminal { help_msg, .. } =>
                help_msg.as_ref().map(|s| s.as_str()).unwrap_or("<no help text provided>"),
            CommandTree::Top(_) => "",
        }
    }
    pub fn get_children(&self) -> &Vec<CommandTree> {
        use CommandTree::*;
        match self {
            Terminal { children, .. } | NonTerminal { children, .. } | Top(children) => children,
        }
    }
    pub fn get_subcommands(&self) -> Vec<&str> {
        self.get_children().iter().map(|x| x.get_cmd()).collect()
    }

    pub fn perform<L: ProgrammingLanguageInterface>(
        &self,
        repl: &mut Repl<L>,
        arguments: &[&str],
    ) -> InterpreterDirectiveOutput {
        let mut dir_pointer: &CommandTree = self;
        let mut idx = 0;

        let res: Result<(DirectiveAction, usize), String> = loop {
            match dir_pointer {
                CommandTree::Top(subcommands) | CommandTree::NonTerminal { children: subcommands, .. } => {
                    let next_command = match arguments.get(idx) {
                        Some(cmd) => cmd,
                        None => break Err("Command requires arguments".to_owned()),
                    };
                    idx += 1;
                    match subcommands.iter().find(|sc| sc.get_cmd() == *next_command) {
                        Some(command_tree) => {
                            dir_pointer = command_tree;
                        }
                        None => break Err(format!("Command {} not found", next_command)),
                    };
                }
                CommandTree::Terminal { action, .. } => {
                    break Ok((action.clone(), idx));
                }
            }
        };

        match res {
            Ok((action, idx)) => action.perform(repl, &arguments[idx..]),
            Err(err) => Some(err.red().to_string()),
        }
    }
}