//! Content lines of iCalendar and vCard text (RFC 5545, 3.1; RFC 6350, 3.2),
//! for edits that must leave every other byte alone.

/// Physical lines joined with their folded continuation lines.
pub(crate) fn logical_lines(text: &str) -> Vec<&str> {
    let mut out = Vec::new();
    let mut start = 0;
    let mut pos = 0;
    for line in text.split_inclusive('\n') {
        if pos > start && !line.starts_with([' ', '\t']) {
            out.push(&text[start..pos]);
            start = pos;
        }
        pos += line.len();
    }
    if pos > start {
        out.push(&text[start..pos]);
    }
    out
}

pub(crate) fn unfold(line: &str) -> String {
    line.replace("\r\n ", "")
        .replace("\r\n\t", "")
        .replace("\n ", "")
        .replace("\n\t", "")
        .trim_end_matches(['\r', '\n'])
        .to_string()
}

/// The property name, upper case.
pub(crate) fn name(line: &str) -> String {
    let end = line.find([':', ';', '\r', '\n']).unwrap_or(line.len());
    line[..end].trim().to_ascii_uppercase()
}

/// Where the value of an unfolded line starts: after the first colon
/// outside a quoted parameter value.
pub(crate) fn value_start(line: &str) -> usize {
    let mut quoted = false;
    for (i, c) in line.char_indices() {
        match c {
            '"' => quoted = !quoted,
            ':' if !quoted => return i + 1,
            _ => {}
        }
    }
    line.len()
}

pub(crate) fn value(line: &str) -> &str {
    &line[value_start(line)..]
}

/// The name and parameters of a line, without the `:` before the value.
pub(crate) fn head(line: &str) -> &str {
    let start = value_start(line);
    line[..start].strip_suffix(':').unwrap_or(line)
}

/// The raw parameters of a line, split at `;` outside quoted values. A
/// quoted TZID may hold `;` and `:`.
pub(crate) fn param_parts(line: &str) -> Vec<&str> {
    let head = head(line);
    let mut parts = Vec::new();
    let (mut quoted, mut start) = (false, 0);
    for (i, c) in head.char_indices() {
        match c {
            '"' => quoted = !quoted,
            ';' if !quoted => {
                parts.push(&head[start..i]);
                start = i + 1;
            }
            _ => {}
        }
    }
    parts.push(&head[start..]);
    parts.remove(0);
    parts
}

/// The value of parameter `key` of an unfolded line, without quotes.
pub(crate) fn param(line: &str, key: &str) -> Option<String> {
    param_parts(line).into_iter().find_map(|p| {
        let (k, v) = p.split_once('=')?;
        k.trim()
            .eq_ignore_ascii_case(key)
            .then(|| v.trim().trim_matches('"').to_string())
    })
}

/// An unfolded line folded at 75 octets (RFC 5545, 3.1), ending in `eol`.
pub(crate) fn fold(line: &str, eol: &str) -> String {
    let mut out = String::with_capacity(line.len() + eol.len() * (line.len() / 74 + 1));
    let mut width = 0;
    for c in line.chars() {
        if width + c.len_utf8() > 75 {
            out.push_str(eol);
            out.push(' ');
            width = 1;
        }
        out.push(c);
        width += c.len_utf8();
    }
    out + eol
}

/// RFC 5545, 3.3.11. A TZID property is TEXT, so `Athens\, Bucharest`
/// there names the TZID parameter `"Athens, Bucharest"`.
pub(crate) fn unescape_text(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    let mut chars = s.chars();
    while let Some(c) = chars.next() {
        match (c, chars.clone().next()) {
            ('\\', Some(n @ ('\\' | ';' | ',' | 'n' | 'N'))) => {
                out.push(if n.eq_ignore_ascii_case(&'n') {
                    '\n'
                } else {
                    n
                });
                chars.next();
            }
            _ => out.push(c),
        }
    }
    out
}

/// RFC 5545, 3.3.11.
pub(crate) fn escape_text(s: &str) -> String {
    s.replace('\\', "\\\\")
        .replace(';', "\\;")
        .replace(',', "\\,")
        .replace('\n', "\\n")
        .replace('\r', "")
}