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use std::collections::HashMap;

use crate::{
    configuration_provider::ConfigurationProvider,
    value::number::Number,
    value::Value,
};

pub struct EnvironmentVariablesProvider {
    prefix: Option<String>,
}

impl EnvironmentVariablesProvider {
    pub fn new() -> Self {
        EnvironmentVariablesProvider { prefix: None }
    }

    pub fn prefixed(prefix: impl ToString) -> Self {
        EnvironmentVariablesProvider {
            prefix: Some(prefix.to_string()),
        }
    }
}

impl ConfigurationProvider for EnvironmentVariablesProvider {
    fn provide(&self) -> Value {
        let map = std::env::vars()
            .filter_map(|(k, v)| {
                let key = match &self.prefix {
                    Some(prefix) => match k.strip_prefix(prefix) {
                        Some(trimmed) => trimmed.to_string(),
                        None => return None,
                    },
                    None => k,
                };

                let value: Option<Value> = parse_env_var_value(&v);

                Some((key, value.unwrap_or(Value::String(v))))
            })
            .collect::<HashMap<String, Value>>();

        Value::Map(map)
    }
}

fn parse_env_var_value(v: &str) -> Option<Value> {
    if let Ok(parsed_value) = v.parse::<bool>() {
        return Some(Value::Bool(parsed_value));
    }

    if let Ok(parsed_value) = v.parse::<u64>() {
        return Some(Value::Number(Number::UInteger(parsed_value)));
    }

    if let Ok(parsed_value) = v.parse::<i64>() {
        return Some(Value::Number(Number::Integer(parsed_value)));
    }

    if let Ok(parsed_value) = v.parse::<f64>() {
        return Some(Value::Number(Number::Float(parsed_value)));
    }

    None
}