use log::trace;
use miette::{IntoDiagnostic, Result};
use nu_engine::{convert_env_values, eval_block};
use nu_parser::parse;
use nu_protocol::{
    engine::{EngineState, StateDelta, StateWorkingSet},
    Config, PipelineData, Span, Value, CONFIG_VARIABLE_ID,
};
use std::path::PathBuf;

use crate::utils::{gather_parent_env_vars, report_error};

/// Main function used when a file path is found as argument for nu
pub(crate) fn evaluate(
    path: String,
    args: &[String],
    init_cwd: PathBuf,
    engine_state: &mut EngineState,
    input: PipelineData,
) -> Result<()> {
    // First, set up env vars as strings only
    gather_parent_env_vars(engine_state);

    let file = std::fs::read(&path).into_diagnostic()?;

    let (block, delta) = {
        let mut working_set = StateWorkingSet::new(engine_state);
        trace!("parsing file: {}", path);

        let (output, err) = parse(&mut working_set, Some(&path), &file, false);
        if let Some(err) = err {
            report_error(&working_set, &err);

            std::process::exit(1);
        }
        (output, working_set.render())
    };

    if let Err(err) = engine_state.merge_delta(delta, None, &init_cwd) {
        let working_set = StateWorkingSet::new(engine_state);
        report_error(&working_set, &err);
    }

    let mut stack = nu_protocol::engine::Stack::new();

    // Set up our initial config to start from
    stack.vars.insert(
        CONFIG_VARIABLE_ID,
        Value::Record {
            cols: vec![],
            vals: vec![],
            span: Span { start: 0, end: 0 },
        },
    );

    let config = match stack.get_config() {
        Ok(config) => config,
        Err(e) => {
            let working_set = StateWorkingSet::new(engine_state);

            report_error(&working_set, &e);
            Config::default()
        }
    };

    // Merge the delta in case env vars changed in the config
    match nu_engine::env::current_dir(engine_state, &stack) {
        Ok(cwd) => {
            if let Err(e) = engine_state.merge_delta(StateDelta::new(), Some(&mut stack), cwd) {
                let working_set = StateWorkingSet::new(engine_state);
                report_error(&working_set, &e);
            }
        }
        Err(e) => {
            let working_set = StateWorkingSet::new(engine_state);
            report_error(&working_set, &e);
        }
    }

    // Translate environment variables from Strings to Values
    if let Some(e) = convert_env_values(engine_state, &stack, &config) {
        let working_set = StateWorkingSet::new(engine_state);
        report_error(&working_set, &e);
        std::process::exit(1);
    }

    // Next, let's check if there are any flags we want to pass to the main function
    if args.is_empty() && engine_state.find_decl(b"main").is_none() {
        // We don't have a main, so evaluate the whole file
        match eval_block(engine_state, &mut stack, &block, input) {
            Ok(pipeline_data) => {
                for item in pipeline_data {
                    if let Value::Error { error } = item {
                        let working_set = StateWorkingSet::new(engine_state);

                        report_error(&working_set, &error);

                        std::process::exit(1);
                    }
                    println!("{}", item.into_string("\n", &config));
                }
            }
            Err(err) => {
                let working_set = StateWorkingSet::new(engine_state);

                report_error(&working_set, &err);

                std::process::exit(1);
            }
        }
    } else {
        let args = format!("main {}", args.join(" ")).as_bytes().to_vec();

        let (block, delta) = {
            let mut working_set = StateWorkingSet::new(engine_state);
            let (output, err) = parse(&mut working_set, Some("<cmdline>"), &args, false);
            if let Some(err) = err {
                report_error(&working_set, &err);

                std::process::exit(1);
            }
            (output, working_set.render())
        };

        let cwd = nu_engine::env::current_dir_str(engine_state, &stack)?;

        if let Err(err) = engine_state.merge_delta(delta, Some(&mut stack), &cwd) {
            let working_set = StateWorkingSet::new(engine_state);
            report_error(&working_set, &err);
        }

        match eval_block(engine_state, &mut stack, &block, input) {
            Ok(pipeline_data) => {
                for item in pipeline_data {
                    if let Value::Error { error } = item {
                        let working_set = StateWorkingSet::new(engine_state);

                        report_error(&working_set, &error);

                        std::process::exit(1);
                    }
                    println!("{}", item.into_string("\n", &config));
                }
            }
            Err(err) => {
                let working_set = StateWorkingSet::new(engine_state);

                report_error(&working_set, &err);

                std::process::exit(1);
            }
        }
    }

    Ok(())
}