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use std::env;
use std::error::Error;
use std::fs;

#[derive(Debug)]
pub struct Config {
    query: String,
    filename: String,
    case_sensitive: bool,
}

impl Config {
    pub fn new(mut args: std::env::Args) -> Result<Config, &'static str> {
        args.next();

        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a query string"),
        };

        let filename = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a file name"),
        };

        // 正常情况不设,所以is_err()返回true,还不如通enum?...
        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

        Ok(Config {
            query,
            filename,
            case_sensitive,
        })
    }

    pub fn query(&self) -> &String {
        &self.query
    }

    pub fn filename(&self) -> &String {
        &self.filename
    }

    pub fn case_sensitive(&self) -> bool {
        self.case_sensitive
    }
}

pub fn run(config: &Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.filename())?;
    //println!("With text:\n{}", contents);
    let results = if config.case_sensitive() {
        search(config.query(), &contents)
    } else {
        search_case_insensitive(config.query(), &contents)
    };
    for line in results {
        println!("{}", line);
    }

    Ok(())
}

fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents.lines()
        .filter(|line| line.contains(query))  // line是形参,可以随便取名,不是capture的值
        .collect()
}

fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();
    contents.lines()
        .filter(|line| line.to_lowercase().contains(&query) )
        .collect()
}

#[cfg(test)]
mod minigrep_test {
    use super::*;

    #[test]
    fn case_sensitive_one_result() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.";
        assert_eq!(vec!["safe, fast, productive."], search(query, contents))
    }

    #[test]
    fn case_sensitive_two_result() {
        let query = "mus";
        let contents = "\
Rust, must:
safe, fast, productive.
MUST
Pick three. must";
        assert_eq!(
            vec!["Rust, must:", "Pick three. must"],
            search(query, contents)
        )
    }

    #[test]
    fn case_insensitive() {
        let query = "MUST";
        let contents = "\
Rust, must:
safe, fast, productive.
MUST
Pick three. must";
        assert_eq!(
            vec!["Rust, must:", "MUST", "Pick three. must"],
            search_case_insensitive(query, contents)
        )
    }
}