sd-switch 0.6.2

use std::fmt::Write as _;
use std::{borrow::Cow, collections::BTreeMap, iter::Peekable, str::Chars};

pub const KEY_REFUSEMANUALSTART: &str = "RefuseManualStart";
pub const KEY_REFUSEMANUALSTOP: &str = "RefuseManualStop";
pub const KEY_X_RELOADIFCHANGED: &str = "X-ReloadIfChanged";
pub const KEY_X_RESTARTIFCHANGED: &str = "X-RestartIfChanged";
pub const KEY_X_STOPIFCHANGED: &str = "X-StopIfChanged";
pub const KEY_X_SWITCHMETHOD: &str = "X-SwitchMethod";

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct SystemdIni(Sections);

type Sections = BTreeMap<String, Entries>;
type Entries = BTreeMap<String, Value>;

#[derive(Debug, Clone, PartialEq, Eq)]
enum Value {
    Strings(Vec<String>),
    SwitchMethod(UnitSwitchMethod),
    Bool(bool),
}

/// How to switch a unit.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum UnitSwitchMethod {
    /// Reload the unit if it is already running, otherwise start it.
    Reload,
    /// Restart the unit if it is already running, otherwise start it.
    Restart,
    /// Stop the old unit (if it exists) and start the new unit.
    StopStart,
    /// Stop the old unit (if it exists) but do not start the new unit
    StopOnly,
    /// Leave the old unit running, ignoring the new unit. If no old unit
    /// exists, then the new unit is started.
    KeepOld,
}

impl SystemdIni {
    pub fn get_bool(&self, section: &str, key: &str) -> Option<bool> {
        self.get_value(section, key).and_then(|v| {
            if let Value::Bool(b) = v {
                Some(*b)
            } else {
                None
            }
        })
    }

    pub fn get_unit_switch_method(&self) -> Option<UnitSwitchMethod> {
        self.get_value("Unit", KEY_X_SWITCHMETHOD).and_then(|v| {
            if let Value::SwitchMethod(b) = v {
                Some(*b)
            } else {
                None
            }
        })
    }

    fn get_value(&self, section: &str, key: &str) -> Option<&Value> {
        self.0.get(section).and_then(|entries| entries.get(key))
    }

    pub fn remove(&mut self, section: &str, key: &str) {
        let _ = self.0.get_mut(section).map(|entries| entries.remove(key));
    }

    /// Merges `other` into `self`.
    ///
    /// Overlapping fields are taken from `other` and `other` is consumed in the process.
    pub fn extend(self: &mut SystemdIni, other: SystemdIni) {
        for (section, entries) in other.0 {
            self.0.entry(section).or_default().extend(entries);
        }
    }

    /// Compares `self` with `other` for equality but excluding the given
    /// options.
    pub fn eq_excluding(&self, other: &SystemdIni, excluded: &[(&str, &str)]) -> bool {
        /// Creates an iterator over all entries, excluding those entries present in `excluded`.
        fn make_eq_iter<'a>(
            ini: &'a SystemdIni,
            excluded: &'a [(&'a str, &'a str)],
        ) -> impl Iterator<Item = ((&'a str, &'a str), &'a Value)> {
            ini.0
                .iter()
                .flat_map(|(section, entries)| {
                    entries
                        .iter()
                        .map(|(key, value)| ((section.as_str(), key.as_str()), value))
                })
                .filter(|(p, _)| !excluded.contains(p))
        }

        let a = make_eq_iter(self, excluded);
        let b = make_eq_iter(other, excluded);

        a.eq(b)
    }
}

struct Parser<'a> {
    content: Peekable<Chars<'a>>,
    line: usize,
    column: usize,
}

#[derive(Debug, PartialEq, Eq)]
pub struct ParseError {
    message: Cow<'static, str>,
    line: usize,
    column: usize,
}

impl std::fmt::Display for ParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(
            f,
            "{} at line {}, column {}",
            self.message, self.line, self.column
        )
    }
}

impl std::error::Error for ParseError {}

impl<'a> Parser<'a> {
    fn eof(&mut self) -> bool {
        self.content.peek().is_none()
    }

    /// Read the next character from the input stream.
    fn next(&mut self) -> Option<char> {
        let ch = self.content.next()?;

        if ch == '\n' {
            self.line += 1;
            self.column = 0;
        } else {
            self.column += 1;
        }

        Some(ch)
    }

    /// Optionally read the next character from the input stream.
    fn next_if<P>(&mut self, p: P) -> Option<char>
    where
        P: FnOnce(&char) -> bool,
    {
        let ch = self.content.next_if(p)?;

        if ch == '\n' {
            self.line += 1;
            self.column = 0;
        } else {
            self.column += 1;
        }

        Some(ch)
    }

    fn error(&self, message: Cow<'static, str>) -> ParseError {
        ParseError {
            message,
            line: self.line,
            column: self.column,
        }
    }

    fn error_unexpected<S: AsRef<str>>(&mut self, expected: S) -> ParseError {
        let message = format!(
            "expected {} but got {}",
            expected.as_ref(),
            if let Some(ch) = self.content.peek() {
                format!("'{ch}'")
            } else {
                "end of file".to_string()
            }
        );

        ParseError {
            message: message.into(),
            line: self.line,
            column: self.column,
        }
    }

    fn expect(&mut self, expected: char) -> Result<(), ParseError> {
        if let Some(ch) = self.content.peek() {
            let ch = *ch;
            if ch == expected {
                self.next();
                return Ok(());
            }
        }

        Err(self.error_unexpected(format!("'{expected}'")))
    }

    // Used by `to_unescaped_string`.
    #[allow(dead_code)]
    fn take(&mut self, n: usize) -> String {
        let mut result = String::new();

        for _ in 0..n {
            if let Some(ch) = self.next() {
                result.push(ch);
            } else {
                break;
            }
        }

        result
    }

    fn take_while<P>(&mut self, p: P) -> String
    where
        P: Fn(&char) -> bool,
    {
        let mut result = String::new();

        while let Some(ch) = self.next_if(&p) {
            result.push(ch);
        }

        result
    }

    fn skip_while<P>(&mut self, p: P)
    where
        P: Fn(&char) -> bool,
    {
        while self.next_if(&p).is_some() {}
    }

    /// Skips all whitespace characters.
    fn skip_ws(&mut self) {
        self.skip_while(|ch| ch.is_ascii_whitespace())
    }

    /// Skip only horizontal whitespace characters (' ' and '\t').
    fn skip_hs(&mut self) {
        self.skip_while(|ch| *ch == ' ' || *ch == '\t')
    }

    /// Skip comment starting with `#` or `;`, if one starts at current position.
    ///
    /// Returns `true` if comment actually was skipped, `false` otherwise.
    fn skip_comment(&mut self) -> bool {
        if self.next_if(|ch| *ch == '#' || *ch == ';').is_some() {
            self.skip_while(|ch| *ch != '\n');
            self.next();
            true
        } else {
            false
        }
    }

    fn parse_section(&mut self) -> Result<Option<(String, Entries)>, ParseError> {
        self.skip_ws();

        while self.skip_comment() {
            self.skip_ws();
        }

        // If we've reached EOF.
        if self.eof() {
            return Ok(None);
        }

        self.expect('[')?;

        let section_name = self
            .take_while(|ch| *ch != ']' && *ch != '\'' && *ch != '\"' && !ch.is_ascii_control());

        self.expect(']')?;
        self.expect('\n')?;
        self.skip_ws();

        let entries = self.parse_section_entries(&section_name)?;

        Ok(Some((section_name, entries)))
    }

    fn parse_section_entries(&mut self, section_name: &str) -> Result<Entries, ParseError> {
        let mut entries = Entries::new();

        while let Some(ch) = self.content.peek() {
            // Have reached start of a new INI section.
            if *ch == '[' {
                break;
            }

            if self.skip_comment() {
                self.skip_ws();
                continue;
            }

            let key = self.parse_entry_key()?;

            if key.is_empty() {
                return Err(self.error_unexpected("entry key name"));
            }

            self.skip_hs();

            self.expect('=')?;

            self.skip_hs();

            let value = self.parse_entry_value()?;

            // Convert the raw string value into the expected INI value.
            match section_name {
                "Unit" => {
                    if [
                        KEY_REFUSEMANUALSTART,
                        KEY_REFUSEMANUALSTOP,
                        KEY_X_RELOADIFCHANGED,
                        KEY_X_RESTARTIFCHANGED,
                        KEY_X_STOPIFCHANGED,
                    ]
                    .contains(&key.as_str())
                    {
                        let value = to_bool(value).map_err(|s| self.error(s.into()))?;
                        entries.insert(key, value);
                    } else if [KEY_X_SWITCHMETHOD].contains(&key.as_str()) {
                        let value =
                            to_unit_switch_method(&value).map_err(|s| self.error(s.into()))?;
                        entries.insert(key, value);
                    } else {
                        let e = entries.entry(key).or_insert_with(|| Value::Strings(vec![]));
                        match e {
                            Value::Strings(items) => items.push(value),
                            _ => panic!("inconsistent key value type"),
                        };
                    }
                }
                _ => {
                    let e = entries.entry(key).or_insert_with(|| Value::Strings(vec![]));
                    match e {
                        Value::Strings(items) => items.push(value),
                        _ => panic!("inconsistent key value type"),
                    };
                }
            };

            self.skip_ws();
        }

        Ok(entries)
    }

    fn parse_entry_key(&mut self) -> Result<String, ParseError> {
        Ok(self.take_while(|c| c.is_ascii_alphanumeric() || *c == '-'))
    }

    /// Parses a entry value.
    ///
    /// Handles line continuations, comments, and escaped characters.
    ///
    /// Additionally, leading and trailing whitespaces are trimmed from the returned
    /// string.
    fn parse_entry_value(&mut self) -> Result<String, ParseError> {
        let mut value = String::with_capacity(16);

        while let Some(ch) = self.next() {
            if ch == '\n' {
                break;
            } else if ch == '\\' {
                let Some(ch) = self.next() else {
                    return Err(self.error("invalid character escape: '\\'".into()));
                };

                match ch {
                    // We are in a line continuation.
                    '\n' => {
                        // Skip whitespace after the \ and replace it with a
                        // single ' '. Also skip any intermediate comment lines.
                        value.push(' ');
                        self.skip_hs();
                        while self.skip_comment() {
                            self.skip_hs();
                        }
                    }
                    // Unknown escapes are passed on verbatim.
                    ch => {
                        value.push('\\');
                        value.push(ch);
                    }
                }
            } else {
                value.push(ch);
            }
        }

        Ok(value.trim().to_string())
    }
}

/// Converts a string to a Boolean using systemd's rules.
///
/// As defined in `systemd.syntax(7)`:
///
/// > Boolean arguments used in configuration files can be written in
/// > various formats. For positive settings the strings 1, yes, true and on
/// > are equivalent. For negative settings, the strings 0, no, false and
/// > off are equivalent.
///
/// Additionally, 'y'/'n' and 't'/'f' seem to be respected by systemd.
fn to_bool(mut value: String) -> Result<Value, String> {
    value.make_ascii_lowercase();
    match value.as_str() {
        "1" | "yes" | "y" | "true" | "t" | "on" => Ok(Value::Bool(true)),
        "0" | "no" | "n" | "false" | "f" | "off" => Ok(Value::Bool(false)),
        _ => Err(format!("invalid Boolean value \"{value}\"")),
    }
}

fn to_unit_switch_method(value: &str) -> Result<Value, String> {
    let value = match value {
        "reload" => Ok(UnitSwitchMethod::Reload),
        "restart" => Ok(UnitSwitchMethod::Restart),
        "stop-start" => Ok(UnitSwitchMethod::StopStart),
        "keep-old" => Ok(UnitSwitchMethod::KeepOld),
        unknown => Err(format!("unknown unit switch method \"{unknown}\"")),
    }?;

    Ok(Value::SwitchMethod(value))
}

/// Unescapes the given string according to the systemd escape rules.
///
/// Specifically, the supported escapes match what is in
/// `systemd.syntax(7)`:
///
/// | Literal    | Actual value                                        |
/// |------------|-----------------------------------------------------|
/// | \a         | bell                                                |
/// | \b         | backspace                                           |
/// | \f         | form feed                                           |
/// | \n         | newline                                             |
/// | \r         | carriage return                                     |
/// | \t         | tab                                                 |
/// | \v         | vertical tab                                        |
/// | \\\\       | backslash                                           |
/// | \\"        | double quotation mark                               |
/// | \\'        | single quotation mark                               |
/// | \s         | space                                               |
/// | \xxx       | character number xx in hexadecimal encoding         |
/// | \nnn       | character number nnn in octal encoding              |
/// | \unnnn     | unicode code point nnnn in hexadecimal encoding     |
/// | \Unnnnnnnn | unicode code point nnnnnnnn in hexadecimal encoding |
///
/// Note, not actually used anywhere but maybe it will be useful in the
/// future?
#[allow(dead_code)]
fn to_unescaped_string(value: &str) -> Result<String, String> {
    let mut result = String::with_capacity(value.len());

    // Current character being escaped (for use of \xxx and \nnn escapes of multi-byte UTF-8 characters).
    let mut cur_escape: Vec<u8> = Vec::with_capacity(4);

    let mut it = value.chars();

    while let Some(ch) = it.next() {
        if ch == '\\' {
            let Some(ch) = it.next() else {
                return Err("invalid character escape: '\\'".into());
            };

            match ch {
                'a' => result.push('\x07'),
                'b' => result.push('\x08'),
                'f' => result.push('\x0C'),
                'n' => result.push('\n'),
                'r' => result.push('\r'),
                't' => result.push('\t'),
                'v' => result.push('\x0B'),
                '\\' => result.push('\\'),
                '"' => result.push('\"'),
                '\'' => result.push('\''),
                's' => result.push(' '),
                'x' => {
                    let hex: String = it.by_ref().take(2).collect();
                    match (hex.len(), u8::from_str_radix(&hex, 16)) {
                        (2, Ok(char_num)) => {
                            cur_escape.push(char_num);
                            match std::str::from_utf8(&cur_escape) {
                                Ok(s) => {
                                    result.push_str(s);
                                    cur_escape.clear();
                                }
                                Err(e) if e.error_len().is_none() => {}
                                Err(_) => {
                                    return Err(format!(
                                        "invalid escaped UTF-8 code point '{}'",
                                        to_hex_string(&cur_escape)
                                    ))
                                }
                            }
                        }
                        _ => return Err(format!("invalid character escape: '\\x{hex}'")),
                    }
                }
                n if ('0'..='7').contains(&n) => {
                    let mut oct = String::with_capacity(3);
                    oct.push(n);
                    oct.push_str(it.by_ref().take(2).collect::<String>().as_str());
                    let oct = oct;

                    match (oct.len(), u16::from_str_radix(&oct, 8)) {
                        (3, Ok(char_num)) if char_num <= 255 => {
                            cur_escape.push(char_num as u8);
                            match std::str::from_utf8(&cur_escape) {
                                Ok(s) => {
                                    result.push_str(s);
                                    cur_escape.clear();
                                }
                                Err(e) if e.error_len().is_none() => {}
                                Err(_) => {
                                    return Err(format!(
                                        "invalid escaped UTF-8 code point '{}'",
                                        to_hex_string(&cur_escape)
                                    ))
                                }
                            }
                        }
                        _ => return Err(format!("invalid character escape: '\\{oct}'")),
                    }
                }
                'u' => {
                    let hex: String = it.by_ref().take(4).collect();
                    match (hex.len(), u32::from_str_radix(&hex, 16).map(char::from_u32)) {
                        (4, Ok(Some(ch))) => result.push(ch),
                        _ => return Err(format!("invalid character escape: '\\u{hex}'")),
                    }
                }
                'U' => {
                    let hex: String = it.by_ref().take(8).collect();
                    match (hex.len(), u32::from_str_radix(&hex, 16).map(char::from_u32)) {
                        (8, Ok(Some(ch))) => result.push(ch),
                        _ => return Err(format!("invalid character escape: '\\U{hex}'")),
                    }
                }
                // Unknown escapes are passed on verbatim.
                ch => {
                    result.push('\\');
                    result.push(ch);
                }
            }
        } else {
            result.push(ch);
        }
    }

    Ok(result)
}

fn to_hex_string(bytes: &[u8]) -> String {
    bytes
        .iter()
        .fold(String::with_capacity(4 * bytes.len()), |mut acc, n| {
            let _ = write!(acc, "\\x{n:02x}");
            acc
        })
}

/// Parses a given string as a systemd INI file.
///
/// The expected format is as described in [XDG Desktop Entry
/// Specification](https://specifications.freedesktop.org/desktop-entry-spec/latest/basic-format.html)
/// and `systemd.syntax(7)`.
pub fn parse(content: &str) -> Result<SystemdIni, ParseError> {
    let mut parser = Parser {
        content: content.chars().peekable(),
        line: 0,
        column: 0,
    };

    let mut sections = BTreeMap::new();

    while let Some((key, entries)) = parser.parse_section()? {
        sections.insert(key, entries);
    }

    Ok(SystemdIni(sections))
}

#[cfg(test)]
mod tests {
    use std::path::PathBuf;

    use super::*;

    fn test_data_path(file_name: &str) -> PathBuf {
        PathBuf::from("testdata/unit_file").join(file_name)
    }

    fn systemd_ini<S: Into<Sections>>(sections: S) -> SystemdIni {
        SystemdIni(sections.into())
    }

    fn section<M: Into<Entries>>(name: &str, entries: M) -> (String, Entries) {
        (name.to_string(), entries.into())
    }

    fn entry(key: &str, value: Value) -> (String, Value) {
        (key.to_string(), value)
    }

    fn entry_str(key: &str, value: &str) -> (String, Value) {
        entry(key, Value::Strings(vec![value.to_string()]))
    }

    fn entry_bool(key: &str, value: bool) -> (String, Value) {
        entry(key, Value::Bool(value))
    }

    #[test]
    fn can_remove_with_empty_section() {
        let mut actual = systemd_ini([section("Section", [])]);
        let expected = actual.clone();

        actual.remove("Missing", "missing");

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_remove_with_missing_key() {
        let mut actual = systemd_ini([section("Section", [entry_str("entry", "value")])]);
        let expected = actual.clone();

        actual.remove("Section", "missing");

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_remove_with_existing_key() {
        let mut actual = systemd_ini([section(
            "Section",
            [entry_str("entry", "value"), entry_str("existing", "value")],
        )]);
        let expected = systemd_ini([section("Section", [entry_str("entry", "value")])]);

        actual.remove("Section", "existing");

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_extend_empty_with_non_empty() {
        let mut actual = systemd_ini([]);
        let mergee = systemd_ini([section("Section", [entry_str("entry", "value")])]);

        let expected = mergee.clone();

        actual.extend(mergee);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_extend_non_empty_with_empty() {
        let mut actual = systemd_ini([section("Section", [entry_str("entry", "value")])]);
        let mergee = systemd_ini([]);

        let expected = actual.clone();

        actual.extend(mergee);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_extend_non_empty_section_with_empty_section() {
        let mut actual = systemd_ini([section("Section", [entry_str("entry", "value")])]);
        let mergee = systemd_ini([section("Section", [])]);

        let expected = actual.clone();

        actual.extend(mergee);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_extend_empty_section_with_non_empty_section() {
        let mut actual = systemd_ini([section("Section", [])]);
        let mergee = systemd_ini([section("Section", [entry_str("entry", "value")])]);

        let expected = mergee.clone();

        actual.extend(mergee);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_extend_non_empty_section_with_non_empty_section() {
        let mut actual = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry2", "value2")],
        )]);
        let mergee = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value2"), entry_str("entry3", "value3")],
        )]);

        let expected = systemd_ini([section(
            "Section",
            [
                entry_str("entry1", "value2"),
                entry_str("entry2", "value2"),
                entry_str("entry3", "value3"),
            ],
        )]);

        actual.extend(mergee);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_eq_excluding_nothing() {
        let a = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry2", "value2")],
        )]);

        let same = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry2", "value2")],
        )]);

        let different_value = systemd_ini([section(
            "Section",
            [
                entry_str("entry1", "value1"),
                entry_str("entry2", "value2'"),
            ],
        )]);

        let different_entry = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry3", "value3")],
        )]);

        assert!(a.eq_excluding(&same, &[]));
        assert!(!a.eq_excluding(&different_value, &[]));
        assert!(!a.eq_excluding(&different_entry, &[]));
    }

    #[test]
    fn can_eq_excluding_one() {
        let a = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry2", "value2")],
        )]);

        let same = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry2", "value2")],
        )]);

        let different_value = systemd_ini([section(
            "Section",
            [
                entry_str("entry1", "value1"),
                entry_str("entry2", "value2'"),
            ],
        )]);

        let different_entry = systemd_ini([section(
            "Section",
            [entry_str("entry1", "value1"), entry_str("entry3", "value3")],
        )]);

        assert!(a.eq_excluding(&same, &[("Section", "entry2")]));
        assert!(a.eq_excluding(&different_value, &[("Section", "entry2")]));
        assert!(!a.eq_excluding(&different_entry, &[("Section", "entry2")]));
    }

    #[test]
    fn can_parse_empty_file() {
        let actual = parse("").unwrap();

        let expected = systemd_ini([]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_file_with_only_comments() {
        let actual = parse(
            r#"
# comment1

; comment2
;
# comment3
"#,
        )
        .unwrap();

        let expected = systemd_ini([]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_empty_section() {
        let actual = parse(
            r#"
[abcde]
"#,
        )
        .unwrap();

        let expected = systemd_ini([section("abcde", [])]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_file_with_comment_on_last_line() {
        let actual = parse(
            r#"
[abcde]
foo = bar
# comment1
; comment2"#,
        )
        .unwrap();

        let expected = systemd_ini([section("abcde", [entry_str("foo", "bar")])]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_section() {
        let ini_no_new_line = r#"
[abcde]
foo = bar
baz = boo"#;
        let ini_new_line = {
            let mut s = String::from(ini_no_new_line);
            s.push('\n');
            s
        };

        let actual_no_new_line = parse(ini_no_new_line).unwrap();
        let actual_new_line = parse(&ini_new_line).unwrap();

        let expected = systemd_ini([section(
            "abcde",
            [entry_str("foo", "bar"), entry_str("baz", "boo")],
        )]);

        assert_eq!(actual_no_new_line, expected);
        assert_eq!(actual_new_line, expected);
    }

    #[test]
    fn fails_for_entry_without_equals() {
        let actual = parse(
            r#"
[abcde]
foo bar
"#,
        );

        let expected = Err(ParseError {
            message: "expected '=' but got 'b'".into(),
            line: 2,
            column: 4,
        });

        assert_eq!(actual, expected);
        assert_eq!(
            format!("{}", actual.unwrap_err()),
            "expected '=' but got 'b' at line 2, column 4"
        );
    }

    #[test]
    fn fails_for_entry_without_key() {
        let actual = parse(
            r#"
[abcde]
 = bar
"#,
        );

        let expected = Err(ParseError {
            message: "expected entry key name but got '='".into(),
            line: 2,
            column: 1,
        });

        assert_eq!(actual, expected);
        assert_eq!(
            format!("{}", actual.unwrap_err()),
            "expected entry key name but got '=' at line 2, column 1"
        );
    }

    #[test]
    fn fails_for_entry_with_bad_boolean() {
        let actual = parse(
            r#"
[Unit]
RefuseManualStart = nonsense
"#,
        );

        let expected = Err(ParseError {
            message: "invalid Boolean value \"nonsense\"".into(),
            line: 3,
            column: 0,
        });

        assert_eq!(actual, expected);
        assert_eq!(
            format!("{}", actual.unwrap_err()),
            "invalid Boolean value \"nonsense\" at line 3, column 0"
        );
    }

    #[test]
    fn fails_for_entry_with_bad_unit_switch_method() {
        let actual = parse(
            r#"
[Unit]
X-SwitchMethod = nonsense
"#,
        );

        let expected = Err(ParseError {
            message: "unknown unit switch method \"nonsense\"".into(),
            line: 3,
            column: 0,
        });

        assert_eq!(actual, expected);
        assert_eq!(
            format!("{}", actual.unwrap_err()),
            "unknown unit switch method \"nonsense\" at line 3, column 0"
        );
    }

    #[test]
    fn can_parse_section_with_list() {
        let actual = parse(
            r#"
[abcde]
foo = bar
foo = baz
"#,
        )
        .unwrap();

        let expected = systemd_ini([section(
            "abcde",
            [entry(
                "foo",
                Value::Strings(vec!["bar".to_string(), "baz".to_string()]),
            )],
        )]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_section_with_line_continuation() {
        let actual1 = parse(
            r#"
[abcde]
foo = bar\
      baz
"#,
        )
        .unwrap();

        let actual2 = parse(
            r#"
[abcde]
foo = bar\
    # An intervening comment should be ignored.
    ; This comment should also be ignored.
      baz
"#,
        )
        .unwrap();

        let expected = systemd_ini([section("abcde", [entry_str("foo", "bar baz")])]);

        assert_eq!(actual1, expected);
        assert_eq!(actual2, expected);
    }

    #[test]
    fn can_unescape_strings() {
        assert_eq!(to_unescaped_string("plain"), Ok("plain".to_string()));

        // Test each escape style bracketed by '<' and '>' to avoid triggering
        // string trimming.
        assert_eq!(to_unescaped_string("<\\a>"), Ok("<\x07>".to_string()));
        assert_eq!(to_unescaped_string("<\\b>"), Ok("<\x08>".to_string()));
        assert_eq!(to_unescaped_string("<\\f>"), Ok("<\x0C>".to_string()));
        assert_eq!(to_unescaped_string("<\\n>"), Ok("<\n>".to_string()));
        assert_eq!(to_unescaped_string("<\\r>"), Ok("<\r>".to_string()));
        assert_eq!(to_unescaped_string("<\\t>"), Ok("<\t>".to_string()));
        assert_eq!(to_unescaped_string("<\\v>"), Ok("<\x0B>".to_string()));
        assert_eq!(to_unescaped_string("<\\\\>"), Ok("<\\>".to_string()));
        assert_eq!(to_unescaped_string("<\\\">"), Ok("<\">".to_string()));
        assert_eq!(to_unescaped_string("<\\'>"), Ok("<\'>".to_string()));
        assert_eq!(to_unescaped_string("<\\s>"), Ok("< >".to_string()));

        assert_eq!(to_unescaped_string("<\\x52>"), Ok("<R>".to_string()));
        assert_eq!(to_unescaped_string("<\\122>"), Ok("<R>".to_string()));
        assert_eq!(to_unescaped_string("<\\u0052>"), Ok("<R>".to_string()));
        assert_eq!(to_unescaped_string("<\\U00000052>"), Ok("<R>".to_string()));

        // Unknown escape is passed on as-is.
        assert_eq!(to_unescaped_string("<\\h>"), Ok("<\\h>".to_string()));

        // Technically the below are more strict than systemd in relaxed mode but
        // probably good to error out for invalid escapes anyway.
        assert_eq!(
            to_unescaped_string("<\\x1>"),
            Err("invalid character escape: '\\x1>'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\199>"),
            Err("invalid character escape: '\\199'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\u123>"),
            Err("invalid character escape: '\\u123>'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\U1234>"),
            Err("invalid character escape: '\\U1234>'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\"),
            Err("invalid character escape: '\\'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\xf0\\xff>"),
            Err("invalid escaped UTF-8 code point '\\xf0\\xff'".into())
        );
        assert_eq!(
            to_unescaped_string("<\\360\\377>"),
            Err("invalid escaped UTF-8 code point '\\xf0\\xff'".into())
        );
    }

    #[test]
    fn can_parse_complicated_systemd_unit() {
        let content = std::fs::read_to_string(test_data_path("escaped-values.service")).unwrap();
        let actual = parse(&content).unwrap();

        let expected = systemd_ini([
            section("Install", [entry_str("WantedBy", "default.target")]),
            section(
                "Service",
                [
                    entry_str(
                        "ExecStart",
                        "/bin/sh -c 'systemd\\x2Dnotify READY=1; /run/current\\x2dsystem/sw/bin/sleep 10s'",
                    ),
                    entry_str("NotifyAccess", "all"),
                    entry_str("Type", "notify"),
                ],
            ),
            section(
                "Unit",
                [
                    entry_str(
                        "Description",
                        "Successful simple service with X-RestartIfChanged = false\\x20\\xf0\\x9f\\x99\\x82",
                    ),
                    entry_bool("RefuseManualStart", false),
                    entry_bool("RefuseManualStop", true),
                    entry("X-SwitchMethod", Value::SwitchMethod(UnitSwitchMethod::Restart)),
                ],
            ),
        ]);

        assert_eq!(actual, expected);
    }

    #[test]
    fn can_parse_upstream_systemd_unit() {
        let content =
            std::fs::read_to_string(test_data_path("systemd-tmpfiles-setup.service")).unwrap();
        let actual = parse(&content).unwrap();

        let expected = systemd_ini([
            section("Install", [entry_str("WantedBy", "basic.target")]),
            section(
                "Service",
                [
                    entry_str("Type", "oneshot"),
                    entry_str(
                        "ExecStart",
                        "systemd-tmpfiles --user --create --remove --boot",
                    ),
                    entry_str("RemainAfterExit", "yes"),
                    entry_str("SuccessExitStatus", "DATAERR"),
                ],
            ),
            section(
                "Unit",
                [
                    entry_str("Description", "Create User Files and Directories"),
                    entry_str("Documentation", "man:tmpfiles.d(5) man:systemd-tmpfiles(8)"),
                    entry_str("DefaultDependencies", "no"),
                    entry_str("Conflicts", "shutdown.target"),
                    entry_str("Before", "basic.target shutdown.target"),
                    entry_bool("RefuseManualStop", true),
                ],
            ),
        ]);

        assert_eq!(actual, expected);
    }
}