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// License: see LICENSE file at root directory of `master` branch

//! # Kit for working with user

use {
    core::{
        fmt::{self, Display, Formatter},
        hash::{Hash, Hasher},
        str::FromStr,
    },
    std::{
        collections::HashSet,
        io::{Error, ErrorKind},
    },

    crate::Result,
};

/// # Answer
///
/// Each variant can have an optional representation string. If not provided, defaults will be used.
///
/// See [`ask_user()`][fn:ask_user] for usage.
///
/// [fn:ask_user]: fn.ask_user.html
#[derive(Debug, Eq)]
pub enum Answer<'a> {

    /// # Yes
    Yes(Option<&'a str>),

    /// # No
    No(Option<&'a str>),

    /// # Retry
    Retry(Option<&'a str>),

    /// # Next
    Next(Option<&'a str>),

    /// # Cancel
    Cancel(Option<&'a str>),

}

impl PartialEq for Answer<'_> {

    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Answer::Yes(_), Answer::Yes(_)) => true,
            (Answer::No(_), Answer::No(_)) => true,
            (Answer::Retry(_), Answer::Retry(_)) => true,
            (Answer::Next(_), Answer::Next(_)) => true,
            (Answer::Cancel(_), Answer::Cancel(_)) => true,
            _ => false,
        }
    }

}

impl Hash for Answer<'_> {

    fn hash<H>(&self, h: &mut H) where H: Hasher {
        let idx: u8 = match self {
            Answer::Yes(_) => 0,
            Answer::No(_) => 1,
            Answer::Retry(_) => 2,
            Answer::Next(_) => 3,
            Answer::Cancel(_) => 4,
        };
        idx.hash(h);
    }

}

#[test]
fn test_answers() {
    let answers = &[
        Answer::Yes(Some(concat!())), Answer::Yes(None),
        Answer::No(Some(concat!())), Answer::No(None),
        Answer::Retry(Some(concat!())), Answer::Retry(None),
        Answer::Next(Some(concat!())), Answer::Next(None),
        Answer::Cancel(Some(concat!())), Answer::Cancel(None),
    ];
    assert_eq!(answers.iter().collect::<HashSet<_>>().len(), 5);
}

impl Display for Answer<'_> {

    fn fmt(&self, f: &mut Formatter) -> core::result::Result<(), fmt::Error> {
        match self {
            Answer::Yes(Some(s)) | Answer::No(Some(s)) | Answer::Retry(Some(s)) | Answer::Next(Some(s)) | Answer::Cancel(Some(s))
            => f.write_str(s),
            Answer::Yes(None) => f.write_str("Yes"),
            Answer::No(None) => f.write_str("No"),
            Answer::Retry(None) => f.write_str("Retry"),
            Answer::Next(None) => f.write_str("Next"),
            Answer::Cancel(None) => f.write_str("Cancel"),
        }
    }

}

/// # Asks user some question
///
/// Notes:
///
/// - The question will be printed first. Then one line break. Then each answer will be printed on each line.
///
/// - The user can enter either:
///
///     + An answer index.
///     + Or some part of an answer.
///
/// - The function will start again if:
///
///     + The user enters a wrong index.
///     + The phrase entered is presented in more than one answer.
///
/// - The function returns an error if you provide duplicate answers, or no answers at all.
pub fn ask_user<'a, 'b, S>(question: S, answers: &'a[Answer<'b>]) -> Result<&'a Answer<'b>> where S: AsRef<str> {
    if answers.is_empty() {
        return Err(Error::new(ErrorKind::InvalidData, "There are no answers"));
    }
    if answers.iter().collect::<HashSet<_>>().len() != answers.len() {
        return Err(Error::new(ErrorKind::InvalidData, "There are duplicate answers"));
    }

    loop {
        crate::lock_write_out(format!("{}\n\n", question.as_ref().trim()))?;
        for (idx, answer) in answers.iter().enumerate() {
            crate::lock_write_out(format!("[{idx}] {answer}\n", idx=idx + 1, answer=answer))?;
        }

        crate::lock_write_out("\n-> ")?;

        let user_choice = crate::read_line::<String>()?;
        if user_choice.is_empty() {
            continue;
        }

        // Try index first
        match usize::from_str(&user_choice).map(|i| i.checked_sub(1)) {
            Ok(Some(idx)) => if idx < answers.len() {
                return Ok(&answers[idx]);
            },
            Ok(None) => continue,
            // Now try phrase
            Err(_) => {
                let user_choice = user_choice.to_lowercase();
                match answers.iter().try_fold(None, |found_answer, answer| if answer.to_string().to_lowercase().contains(&user_choice) {
                    match found_answer {
                        None => Ok(Some(answer)),
                        Some(_) => Err(Error::new(ErrorKind::Other, "User choice matches more than one answer")),
                    }
                } else {
                    Ok(found_answer)
                }) {
                    Ok(Some(answer)) => return Ok(answer),
                    _ => continue,
                };
            },
        };
    }
}