use nu_engine::{current_dir, CallExt};
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, SyntaxShape, Value};

/// Source a file for environment variables.
#[derive(Clone)]
pub struct Exit;

impl Command for Exit {
    fn name(&self) -> &str {
        "exit"
    }

    fn signature(&self) -> Signature {
        Signature::build("exit")
            .optional(
                "exit_code",
                SyntaxShape::Int,
                "Exit code to return immediately with",
            )
            .switch("now", "Exit out of the shell immediately", Some('n'))
            .category(Category::Shells)
    }

    fn usage(&self) -> &str {
        "Runs a script file in the current context."
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        _input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let exit_code: Option<i64> = call.opt(engine_state, stack, 0)?;

        if let Some(exit_code) = exit_code {
            std::process::exit(exit_code as i32);
        }

        if call.has_flag("now") {
            std::process::exit(0);
        }

        let cwd = current_dir(engine_state, stack)?;
        let cwd = Value::String {
            val: cwd.to_string_lossy().to_string(),
            span: call.head,
        };

        let shells = stack.get_env_var(engine_state, "NUSHELL_SHELLS");
        let mut shells = if let Some(v) = shells {
            v.as_list()
                .map(|x| x.to_vec())
                .unwrap_or_else(|_| vec![cwd])
        } else {
            vec![cwd]
        };

        let current_shell = stack.get_env_var(engine_state, "NUSHELL_CURRENT_SHELL");
        let mut current_shell = if let Some(v) = current_shell {
            v.as_integer().unwrap_or_default() as usize
        } else {
            0
        };

        shells.remove(current_shell);

        if current_shell == shells.len() && !shells.is_empty() {
            current_shell -= 1;
        }

        if shells.is_empty() {
            std::process::exit(0);
        } else {
            let new_path = shells[current_shell].clone();

            stack.add_env_var(
                "NUSHELL_SHELLS".into(),
                Value::List {
                    vals: shells,
                    span: call.head,
                },
            );
            stack.add_env_var(
                "NUSHELL_CURRENT_SHELL".into(),
                Value::Int {
                    val: current_shell as i64,
                    span: call.head,
                },
            );

            stack.add_env_var("PWD".into(), new_path);

            Ok(PipelineData::new(call.head))
        }
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Exit the current shell",
                example: "exit",
                result: None,
            },
            Example {
                description: "Exit all shells (exiting Nu)",
                example: "exit --now",
                result: None,
            },
        ]
    }
}