// Copyright © 2020 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0
//

use std::collections::HashMap;
use std::fmt::{Display, Write};
use std::num::ParseIntError;
use std::str::FromStr;

use thiserror::Error;

mod private_trait {
    // Voldemort trait that dispatches to `FromStr::from_str` on externally-defined types
    // and to custom parsing code for types in this module.
    pub trait Parseable
    where
        Self: Sized,
    {
        type Err;
        // Actually does the parsing, but panics if the input doesn't have
        // balanced quotes.  This is fine because split_commas checks that the
        // input has balanced quotes, and option names cannot contain anything
        // that split_commas treats as special.
        fn from_str(input: &str) -> Result<Self, <Self as Parseable>::Err>;
    }
}
use private_trait::Parseable;

#[derive(Default)]
pub struct OptionParser {
    options: HashMap<String, OptionParserValue>,
}

struct OptionParserValue {
    value: Option<String>,
    requires_value: bool,
}

#[derive(Debug, Error)]
pub enum OptionParserError {
    #[error("unknown option: {0}")]
    UnknownOption(String),
    #[error("unknown option: {0}")]
    InvalidSyntax(String),
    #[error("unable to convert {1} for {0}")]
    Conversion(String /* field */, String /* value */),
    #[error("invalid value: {0}")]
    InvalidValue(String),
}
type OptionParserResult<T> = std::result::Result<T, OptionParserError>;

fn split_commas(s: &str) -> OptionParserResult<Vec<String>> {
    let mut list: Vec<String> = Vec::new();
    let mut opened_brackets = 0u64;
    let mut in_quotes = false;
    let mut current = String::new();

    for c in s.trim().chars() {
        match c {
            // In quotes, only '"' is special
            '"' => in_quotes = !in_quotes,
            _ if in_quotes => {}
            '[' => opened_brackets += 1,
            ']' => {
                if opened_brackets < 1 {
                    return Err(OptionParserError::InvalidSyntax(s.to_owned()));
                }
                opened_brackets -= 1;
            }
            ',' if opened_brackets == 0 => {
                list.push(current);
                current = String::new();
                continue;
            }
            _ => {}
        }
        current.push(c);
    }
    list.push(current);

    if in_quotes || opened_brackets != 0 {
        return Err(OptionParserError::InvalidSyntax(s.to_owned()));
    }

    Ok(list)
}

impl OptionParser {
    pub fn new() -> Self {
        Self {
            options: HashMap::new(),
        }
    }

    pub fn parse(&mut self, input: &str) -> OptionParserResult<()> {
        if input.trim().is_empty() {
            return Ok(());
        }

        for option in split_commas(input)?.iter() {
            let parts: Vec<&str> = option.splitn(2, '=').collect();
            match self.options.get_mut(parts[0]) {
                None => return Err(OptionParserError::UnknownOption(parts[0].to_owned())),
                Some(value) => {
                    if value.requires_value {
                        if parts.len() != 2 {
                            return Err(OptionParserError::InvalidSyntax((*option).to_owned()));
                        }
                        value.value = Some(parts[1].trim().to_owned());
                    } else {
                        value.value = Some(String::new());
                    }
                }
            }
        }

        Ok(())
    }

    pub fn add(&mut self, option: &str) -> &mut Self {
        // Check that option=value has balanced
        // quotes and brackets iff value does.
        assert!(
            !option.contains(['"', '[', ']', '=', ',']),
            "forbidden character in option name"
        );
        self.options.insert(
            option.to_owned(),
            OptionParserValue {
                value: None,
                requires_value: true,
            },
        );

        self
    }

    pub fn add_valueless(&mut self, option: &str) -> &mut Self {
        self.options.insert(
            option.to_owned(),
            OptionParserValue {
                value: None,
                requires_value: false,
            },
        );

        self
    }

    pub fn get(&self, option: &str) -> Option<String> {
        self.options
            .get(option)
            .and_then(|v| v.value.clone())
            .and_then(|s| {
                if s.is_empty() {
                    None
                } else {
                    Some(dequote(&s))
                }
            })
    }

    pub fn is_set(&self, option: &str) -> bool {
        self.options
            .get(option)
            .and_then(|v| v.value.as_ref())
            .is_some()
    }

    pub fn convert<T: Parseable>(&self, option: &str) -> OptionParserResult<Option<T>> {
        match self.options.get(option).and_then(|v| v.value.as_ref()) {
            None => Ok(None),
            Some(v) => {
                Ok(if v.is_empty() {
                    None
                } else {
                    Some(Parseable::from_str(v).map_err(|_| {
                        OptionParserError::Conversion(option.to_owned(), v.to_owned())
                    })?)
                })
            }
        }
    }
}

pub struct Toggle(pub bool);

#[derive(Error, Debug)]
pub enum ToggleParseError {
    #[error("invalid value: {0}")]
    InvalidValue(String),
}

impl Parseable for Toggle {
    type Err = ToggleParseError;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        match s.to_lowercase().as_str() {
            "" => Ok(Toggle(false)),
            "on" => Ok(Toggle(true)),
            "off" => Ok(Toggle(false)),
            "true" => Ok(Toggle(true)),
            "false" => Ok(Toggle(false)),
            _ => Err(ToggleParseError::InvalidValue(s.to_owned())),
        }
    }
}

pub struct ByteSized(pub u64);

#[derive(Error, Debug)]
pub enum ByteSizedParseError {
    #[error("invalid value: {0}")]
    InvalidValue(String),
}

impl FromStr for ByteSized {
    type Err = ByteSizedParseError;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        Ok(ByteSized({
            let s = s.trim();
            let shift = if s.ends_with('K') {
                10
            } else if s.ends_with('M') {
                20
            } else if s.ends_with('G') {
                30
            } else {
                0
            };

            let s = s.trim_end_matches(['K', 'M', 'G']);
            s.parse::<u64>()
                .map_err(|_| ByteSizedParseError::InvalidValue(s.to_owned()))?
                << shift
        }))
    }
}

pub struct IntegerList(pub Vec<u64>);

impl Display for IntegerList {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_char('[')?;
        let mut iter = self.0.iter();
        if let Some(first) = iter.next() {
            first.fmt(f)?;
            for i in iter {
                f.write_char(',')?;
                i.fmt(f)?;
            }
        }
        f.write_char(']')
    }
}

#[derive(Error, Debug)]
pub enum IntegerListParseError {
    #[error("invalid value: {0}")]
    InvalidValue(String),
}

impl Parseable for IntegerList {
    type Err = IntegerListParseError;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        let mut integer_list = Vec::new();
        let ranges_list: Vec<&str> = s
            .trim()
            .trim_matches(|c| c == '[' || c == ']')
            .split(',')
            .collect();

        for range in ranges_list.iter() {
            let items: Vec<&str> = range.split('-').collect();

            if items.len() > 2 {
                return Err(IntegerListParseError::InvalidValue((*range).to_string()));
            }

            let start_range = items[0]
                .parse::<u64>()
                .map_err(|_| IntegerListParseError::InvalidValue(items[0].to_owned()))?;

            integer_list.push(start_range);

            if items.len() == 2 {
                let end_range = items[1]
                    .parse::<u64>()
                    .map_err(|_| IntegerListParseError::InvalidValue(items[1].to_owned()))?;
                if start_range >= end_range {
                    return Err(IntegerListParseError::InvalidValue((*range).to_string()));
                }

                for i in start_range..end_range {
                    integer_list.push(i + 1);
                }
            }
        }

        Ok(IntegerList(integer_list))
    }
}

pub trait TupleValue {
    fn parse_value(input: &str) -> Result<Self, TupleError>
    where
        Self: Sized;
}

impl TupleValue for u64 {
    fn parse_value(input: &str) -> Result<Self, TupleError> {
        input.parse::<u64>().map_err(TupleError::InvalidInteger)
    }
}

impl TupleValue for Vec<u8> {
    fn parse_value(input: &str) -> Result<Self, TupleError> {
        Ok(IntegerList::from_str(input)
            .map_err(TupleError::InvalidIntegerList)?
            .0
            .iter()
            .map(|v| *v as u8)
            .collect())
    }
}

impl TupleValue for Vec<u64> {
    fn parse_value(input: &str) -> Result<Self, TupleError> {
        Ok(IntegerList::from_str(input)
            .map_err(TupleError::InvalidIntegerList)?
            .0)
    }
}

impl TupleValue for Vec<usize> {
    fn parse_value(input: &str) -> Result<Self, TupleError> {
        Ok(IntegerList::from_str(input)
            .map_err(TupleError::InvalidIntegerList)?
            .0
            .iter()
            .map(|v| *v as usize)
            .collect())
    }
}

#[derive(PartialEq, Eq, Debug)]
pub struct Tuple<S, T>(pub Vec<(S, T)>);

#[derive(Error, Debug)]
pub enum TupleError {
    #[error("invalid value: {0}")]
    InvalidValue(String),
    #[error("split outside brackets")]
    SplitOutsideBrackets(#[source] OptionParserError),
    #[error("invalid integer list")]
    InvalidIntegerList(#[source] IntegerListParseError),
    #[error("invalid integer")]
    InvalidInteger(#[source] ParseIntError),
}

impl<S: Parseable, T: TupleValue> Parseable for Tuple<S, T> {
    type Err = TupleError;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        let mut list: Vec<(S, T)> = Vec::new();
        let body = s
            .trim()
            .strip_prefix('[')
            .and_then(|s| s.strip_suffix(']'))
            .ok_or_else(|| TupleError::InvalidValue(s.to_string()))?;
        let tuples_list = split_commas(body).map_err(TupleError::SplitOutsideBrackets)?;
        for tuple in tuples_list.iter() {
            let mut in_quotes = false;
            let mut last_idx = 0;
            let mut first_val = None;
            for (idx, c) in tuple.as_bytes().iter().enumerate() {
                match c {
                    b'"' => in_quotes = !in_quotes,
                    b'@' if !in_quotes => {
                        if last_idx != 0 {
                            return Err(TupleError::InvalidValue((*tuple).to_string()));
                        }
                        first_val = Some(&tuple[last_idx..idx]);
                        last_idx = idx + 1;
                    }
                    _ => {}
                }
            }
            let item1 = <S as Parseable>::from_str(
                first_val.ok_or(TupleError::InvalidValue((*tuple).to_string()))?,
            )
            .map_err(|_| TupleError::InvalidValue(first_val.unwrap().to_owned()))?;
            let item2 = TupleValue::parse_value(&tuple[last_idx..])?;
            list.push((item1, item2));
        }

        Ok(Tuple(list))
    }
}

#[derive(Default)]
pub struct StringList(pub Vec<String>);

#[derive(Error, Debug)]
pub enum StringListParseError {
    #[error("invalid value: {0}")]
    InvalidValue(String),
}

fn dequote(s: &str) -> String {
    let mut prev_byte = b'\0';
    let mut in_quotes = false;
    let mut out: Vec<u8> = vec![];
    for i in s.bytes() {
        if i == b'"' {
            if prev_byte == b'"' && !in_quotes {
                out.push(b'"');
            }
            in_quotes = !in_quotes;
        } else {
            out.push(i);
        }
        prev_byte = i;
    }
    assert!(!in_quotes, "split_commas didn't reject unbalanced quotes");
    // SAFETY: the non-ASCII bytes in the output are the same
    // and in the same order as those in the input, so if the
    // input is valid UTF-8 the output will be as well.
    unsafe { String::from_utf8_unchecked(out) }
}

impl<T> Parseable for T
where
    T: FromStr + Sized,
{
    type Err = <T as FromStr>::Err;
    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        dequote(s).parse()
    }
}

impl Parseable for StringList {
    type Err = StringListParseError;

    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        let string_list: Vec<String> =
            split_commas(s.trim().trim_matches(|c| c == '[' || c == ']'))
                .map_err(|_| StringListParseError::InvalidValue(s.to_owned()))?
                .iter()
                .map(|e| e.to_owned())
                .collect();

        Ok(StringList(string_list))
    }
}

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

    #[test]
    fn test_option_parser() {
        let mut parser = OptionParser::new();
        parser
            .add("size")
            .add("mergeable")
            .add("hotplug_method")
            .add("hotplug_size")
            .add("topology")
            .add("cmdline");

        assert_eq!(split_commas("\"\"").unwrap(), vec!["\"\""]);
        parser.parse("size=128M,hanging_param").unwrap_err();
        parser
            .parse("size=128M,too_many_equals=foo=bar")
            .unwrap_err();
        parser.parse("size=128M,file=/dev/shm").unwrap_err();

        parser.parse("size=128M").unwrap();
        assert_eq!(parser.get("size"), Some("128M".to_owned()));
        assert!(!parser.is_set("mergeable"));
        assert!(parser.is_set("size"));
        parser.parse("size=").unwrap();
        assert!(parser.get("size").is_none());

        parser.parse("size=128M,mergeable=on").unwrap();
        assert_eq!(parser.get("size"), Some("128M".to_owned()));
        assert_eq!(parser.get("mergeable"), Some("on".to_owned()));

        parser
            .parse("size=128M,mergeable=on,topology=[1,2]")
            .unwrap();
        assert_eq!(parser.get("size"), Some("128M".to_owned()));
        assert_eq!(parser.get("mergeable"), Some("on".to_owned()));
        assert_eq!(parser.get("topology"), Some("[1,2]".to_owned()));

        parser
            .parse("size=128M,mergeable=on,topology=[[1,2],[3,4]]")
            .unwrap();
        assert_eq!(parser.get("size"), Some("128M".to_owned()));
        assert_eq!(parser.get("mergeable"), Some("on".to_owned()));
        assert_eq!(parser.get("topology"), Some("[[1,2],[3,4]]".to_owned()));

        parser.parse("topology=[").unwrap_err();
        parser.parse("topology=[[[]]]]").unwrap_err();
        parser.parse("topology=[\"@\"\"b\"@[1,2]]").unwrap();
        assert_eq!(
            parser
                .convert::<Tuple<String, Vec<u8>>>("topology")
                .unwrap()
                .unwrap(),
            Tuple(vec![("@\"b".to_owned(), vec![1, 2])])
        );

        parser.parse("cmdline=\"console=ttyS0,9600n8\"").unwrap();
        assert_eq!(
            parser.get("cmdline"),
            Some("console=ttyS0,9600n8".to_owned())
        );
        parser.parse("cmdline=\"").unwrap_err();
        parser.parse("cmdline=\"\"\"").unwrap_err();
    }

    #[test]
    fn parse_bytes() {
        assert_eq!(<String as Parseable>::from_str("a=\"b\"").unwrap(), "a=b");
    }

    #[test]
    fn check_dequote() {
        assert_eq!(dequote("a\u{3b2}\"a\"\"\""), "a\u{3b2}a\"");
    }
}