use super::{Context, Module};

use crate::config::ModuleConfig;
use crate::configs::env_var::EnvVarConfig;
use crate::formatter::StringFormatter;
use crate::segment::Segment;

/// Creates `env_var_module` displayer which displays all configured environmental variables
pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
    let config_table = context.config.get_env_var_modules()?;
    let mut env_modules = config_table
        .iter()
        .filter(|(_, config)| config.is_table())
        .filter_map(|(variable, _)| env_var_module(vec!["env_var", variable], context))
        .collect::<Vec<Module>>();
    // Old configuration is present in starship configuration
    if config_table.iter().any(|(_, config)| !config.is_table()) {
        if let Some(fallback_env_var_module) = env_var_module(vec!["env_var"], context) {
            env_modules.push(fallback_env_var_module);
        }
    }
    Some(env_var_displayer(env_modules, context))
}

/// A utility module to display multiple `env_variable` modules
fn env_var_displayer<'a>(modules: Vec<Module>, context: &'a Context) -> Module<'a> {
    let mut module = context.new_module("env_var_displayer");

    let module_segments = modules
        .into_iter()
        .flat_map(|module| module.segments)
        .collect::<Vec<Segment>>();
    module.set_segments(module_segments);
    module
}

/// Creates a module with the value of the chosen environment variable
///
/// Will display the environment variable's value if all of the following criteria are met:
///     - `env_var.disabled` is absent or false
///     - `env_var.variable` is defined
///     - a variable named as the value of `env_var.variable` is defined
fn env_var_module<'a>(module_config_path: Vec<&str>, context: &'a Context) -> Option<Module<'a>> {
    let mut module = context.new_module(&module_config_path.join("."));
    let config_value = context.config.get_config(&module_config_path);
    let config = EnvVarConfig::load(config_value.expect(
        "modules::env_var::module should only be called after ensuring that the module exists",
    ));

    if config.disabled {
        return None;
    };

    let variable_name = get_variable_name(module_config_path, &config);

    let env_value = get_env_value(context, variable_name?, config.default)?;
    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
        formatter
            .map_meta(|var, _| match var {
                "symbol" => Some(config.symbol),
                _ => None,
            })
            .map_style(|variable| match variable {
                "style" => Some(Ok(config.style)),
                _ => None,
            })
            .map(|variable| match variable {
                "env_value" => Some(Ok(&env_value)),
                _ => None,
            })
            .parse(None, Some(context))
    });

    module.set_segments(match parsed {
        Ok(segments) => segments,
        Err(error) => {
            log::warn!("Error in module `env_var`:\n{}", error);
            return None;
        }
    });

    Some(module)
}

fn get_variable_name<'a>(
    module_config_path: Vec<&'a str>,
    config: &'a EnvVarConfig,
) -> Option<&'a str> {
    match config.variable {
        Some(v) => Some(v),
        None => {
            let last_element = module_config_path.last()?;
            Some(*last_element)
        }
    }
}

fn get_env_value(context: &Context, name: &str, default: Option<&str>) -> Option<String> {
    match context.get_env(name) {
        Some(value) => Some(value),
        None => default.map(std::borrow::ToOwned::to_owned),
    }
}

#[cfg(test)]
mod test {
    use crate::test::ModuleRenderer;
    use nu_ansi_term::{Color, Style};

    const TEST_VAR_VALUE: &str = "astronauts";

    #[test]
    fn empty_config() {
        let actual = ModuleRenderer::new("env_var").collect();
        let expected = None;

        assert_eq!(expected, actual);
    }

    #[test]
    fn fallback_config() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var]
                variable="TEST_VAR"
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!("with {} ", style().paint(TEST_VAR_VALUE)));

        assert_eq!(expected, actual);
    }

    #[test]
    fn defined_variable() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!("with {} ", style().paint(TEST_VAR_VALUE)));

        assert_eq!(expected, actual);
    }

    #[test]
    fn undefined_variable() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
            })
            .collect();
        let expected = None;

        assert_eq!(expected, actual);
    }

    #[test]
    fn default_has_no_effect() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
                default = "N/A"
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!("with {} ", style().paint(TEST_VAR_VALUE)));

        assert_eq!(expected, actual);
    }

    #[test]
    fn default_takes_effect() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.UNDEFINED_TEST_VAR]
                default = "N/A"
            })
            .collect();
        let expected = Some(format!("with {} ", style().paint("N/A")));

        assert_eq!(expected, actual);
    }

    #[test]
    fn symbol() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
                format = "with [■ $env_value](black bold dimmed) "
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!(
            "with {} ",
            style().paint(format!("■ {TEST_VAR_VALUE}"))
        ));

        assert_eq!(expected, actual);
    }

    #[test]
    fn prefix() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
                format = "with [_$env_value](black bold dimmed) "
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!(
            "with {} ",
            style().paint(format!("_{TEST_VAR_VALUE}"))
        ));

        assert_eq!(expected, actual);
    }

    #[test]
    fn suffix() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
                format = "with [${env_value}_](black bold dimmed) "
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!(
            "with {} ",
            style().paint(format!("{TEST_VAR_VALUE}_"))
        ));

        assert_eq!(expected, actual);
    }

    #[test]
    fn display_few() {
        let actual = ModuleRenderer::new("env_var")
            .config(toml::toml! {
                [env_var.TEST_VAR]
                [env_var.TEST_VAR2]
            })
            .env("TEST_VAR", TEST_VAR_VALUE)
            .env("TEST_VAR2", TEST_VAR_VALUE)
            .collect();
        let expected = Some(format!(
            "with {} with {} ",
            style().paint(TEST_VAR_VALUE),
            style().paint(TEST_VAR_VALUE)
        ));

        assert_eq!(expected, actual);
    }

    fn style() -> Style {
        // default style
        Color::Black.bold().dimmed()
    }
}