include_webdir_macros 0.1.0

//! Code copied from include_dir_macros 0.7.4.
//!
//! <https://docs.rs/include_dir_macros/0.7.4/src/include_dir_macros/lib.rs.html>

#![cfg_attr(feature = "nightly", feature(track_path, proc_macro_tracked_env))]

use std::{
    error::Error,
    fmt::{self, Display, Formatter},
    path::PathBuf,
};

pub(crate) fn unwrap_string_literal(lit: &proc_macro::Literal) -> String {
    let mut repr = lit.to_string();
    if !repr.starts_with('"') || !repr.ends_with('"') {
        panic!("This macro only accepts a single, non-empty string argument")
    }

    repr.remove(0);
    repr.pop();

    repr
}

pub(crate) fn resolve_path(
    raw: &str,
    get_env: impl Fn(&str) -> Option<String>,
) -> Result<PathBuf, Box<dyn Error>> {
    let mut unprocessed = raw;
    let mut resolved = String::new();

    while let Some(dollar_sign) = unprocessed.find('$') {
        let (head, tail) = unprocessed.split_at(dollar_sign);
        resolved.push_str(head);

        match parse_identifier(&tail[1..]) {
            Some((variable, rest)) => {
                let value = get_env(variable).ok_or_else(|| MissingVariable {
                    variable: variable.to_string(),
                })?;
                resolved.push_str(&value);
                unprocessed = rest;
            }
            None => {
                return Err(UnableToParseVariable { rest: tail.into() }.into());
            }
        }
    }
    resolved.push_str(unprocessed);

    Ok(PathBuf::from(resolved))
}

#[derive(Debug, PartialEq)]
struct MissingVariable {
    variable: String,
}

impl Error for MissingVariable {}

impl Display for MissingVariable {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        write!(f, "Unable to resolve ${}", self.variable)
    }
}

#[derive(Debug, PartialEq)]
struct UnableToParseVariable {
    rest: String,
}

impl Error for UnableToParseVariable {}

impl Display for UnableToParseVariable {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        write!(f, "Unable to parse a variable from \"{}\"", self.rest)
    }
}

fn parse_identifier(text: &str) -> Option<(&str, &str)> {
    let mut calls = 0;

    let (head, tail) = take_while(text, |c| {
        calls += 1;

        match c {
            '_' => true,
            letter if letter.is_ascii_alphabetic() => true,
            digit if digit.is_ascii_digit() && calls > 1 => true,
            _ => false,
        }
    });

    if head.is_empty() {
        None
    } else {
        Some((head, tail))
    }
}

fn take_while(s: &str, mut predicate: impl FnMut(char) -> bool) -> (&str, &str) {
    let mut index = 0;

    for c in s.chars() {
        if predicate(c) {
            index += c.len_utf8();
        } else {
            break;
        }
    }

    s.split_at(index)
}

#[cfg(feature = "nightly")]
pub(crate) fn get_env(variable: &str) -> Option<String> {
    proc_macro::tracked_env::var(variable).ok()
}

#[cfg(not(feature = "nightly"))]
pub(crate) fn get_env(variable: &str) -> Option<String> {
    std::env::var(variable).ok()
}

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

    #[test]
    fn resolve_path_with_no_environment_variables() {
        let path = "./file.txt";

        let resolved = resolve_path(path, |_| unreachable!()).unwrap();

        assert_eq!(resolved.to_str().unwrap(), path);
    }

    #[test]
    fn simple_environment_variable() {
        let path = "./$VAR";

        let resolved = resolve_path(path, |name| {
            assert_eq!(name, "VAR");
            Some("file.txt".to_string())
        })
        .unwrap();

        assert_eq!(resolved.to_str().unwrap(), "./file.txt");
    }

    #[test]
    fn dont_resolve_recursively() {
        let path = "./$TOP_LEVEL.txt";

        let resolved = resolve_path(path, |name| match name {
            "TOP_LEVEL" => Some("$NESTED".to_string()),
            "$NESTED" => unreachable!("Shouldn't resolve recursively"),
            _ => unreachable!(),
        })
        .unwrap();

        assert_eq!(resolved.to_str().unwrap(), "./$NESTED.txt");
    }

    #[test]
    fn parse_valid_identifiers() {
        let inputs = vec![
            ("a", "a"),
            ("a_", "a_"),
            ("_asf", "_asf"),
            ("a1", "a1"),
            ("a1_#sd", "a1_"),
        ];

        for (src, expected) in inputs {
            let (got, rest) = parse_identifier(src).unwrap();
            assert_eq!(got.len() + rest.len(), src.len());
            assert_eq!(got, expected);
        }
    }

    #[test]
    fn unknown_environment_variable() {
        let path = "$UNKNOWN";

        let err = resolve_path(path, |_| None).unwrap_err();

        let missing_variable = err.downcast::<MissingVariable>().unwrap();
        assert_eq!(
            *missing_variable,
            MissingVariable {
                variable: String::from("UNKNOWN"),
            }
        );
    }

    #[test]
    fn invalid_variables() {
        let inputs = &["$1", "$"];

        for input in inputs {
            let err = resolve_path(input, |_| unreachable!()).unwrap_err();

            let err = err.downcast::<UnableToParseVariable>().unwrap();
            assert_eq!(
                *err,
                UnableToParseVariable {
                    rest: input.to_string(),
                }
            );
        }
    }
}