// Copyright 2020 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::fs::File;
use std::io::{BufRead, BufReader, Read};

pub(crate) fn read_file_to_array(path: &str) -> Result<Vec<String>, String> {
    let file = File::open(path).map_err(|e| e.to_string()).map_err(|err| {
        format!(
            "{} reading path: {:?}, current directory: {:?}",
            err,
            path,
            std::env::current_dir()
        )
    })?;

    read_to_array(file)
}

pub(crate) fn read_stamp_status_to_array(path: String) -> Result<Vec<(String, String)>, String> {
    let file = File::open(path).map_err(|e| e.to_string())?;
    stamp_status_to_array(file)
}

fn read_to_array(reader: impl Read) -> Result<Vec<String>, String> {
    let reader = BufReader::new(reader);
    let mut ret = vec![];
    let mut escaped_line = String::new();
    for l in reader.lines() {
        let line = l.map_err(|e| e.to_string())?;
        if line.is_empty() {
            continue;
        }
        // a \ at the end of a line allows us to escape the new line break,
        // \\ yields a single \, so \\\ translates to a single \ and a new line
        // escape
        let end_backslash_count = line.chars().rev().take_while(|&c| c == '\\').count();
        // a 0 or even number of backslashes do not lead to a new line escape
        let escape = end_backslash_count % 2 == 1;
        //  remove backslashes and add back two for every one
        let l = line.trim_end_matches('\\');
        escaped_line.push_str(l);
        for _ in 0..end_backslash_count / 2 {
            escaped_line.push('\\');
        }
        if escape {
            // we add a newline as we expect a line after this
            escaped_line.push('\n');
        } else {
            ret.push(escaped_line);
            escaped_line = String::new();
        }
    }
    Ok(ret)
}

fn stamp_status_to_array(reader: impl Read) -> Result<Vec<(String, String)>, String> {
    let escaped_lines = read_to_array(reader)?;
    escaped_lines
        .into_iter()
        .map(|l| {
            let (s1, s2) = l
                .split_once(' ')
                .ok_or_else(|| format!("wrong workspace status file format for \"{}\"", l))?;
            Ok((s1.to_owned(), s2.to_owned()))
        })
        .collect()
}

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

    #[test]
    fn test_read_to_array() {
        let input = r#"some escaped \\\
string
with other lines"#
            .to_owned();
        let expected = vec![
            r#"some escaped \
string"#,
            "with other lines",
        ];
        let got = read_to_array(input.as_bytes()).unwrap();
        assert_eq!(expected, got);
    }

    #[test]
    fn test_stamp_status_to_array() {
        let lines = "aaa bbb\\\nvvv\nccc ddd\neee fff";
        let got = stamp_status_to_array(lines.as_bytes()).unwrap();
        let expected = vec![
            ("aaa".to_owned(), "bbb\nvvv".to_owned()),
            ("ccc".to_owned(), "ddd".to_owned()),
            ("eee".to_owned(), "fff".to_owned()),
        ];
        assert_eq!(expected, got);
    }
}