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//! # converter
//!
//! The module which converts the shell script to windows batch script.
//!

#[cfg(test)]
#[path = "./converter_test.rs"]
mod converter_test;

use regex::Regex;

static SHELL2BATCH_PREFIX: &str = "# shell2batch:";

fn replace_flags(arguments: &str, flags_mappings: Vec<(&str, &str)>) -> String {
    let mut windows_arguments = arguments.clone().to_string();

    for flags in flags_mappings {
        let (shell_flag, windows_flag) = flags;

        windows_arguments = match Regex::new(shell_flag) {
            Ok(shell_regex) => {
                let str_value = &shell_regex.replace_all(&windows_arguments, windows_flag);
                str_value.to_string()
            }
            Err(_) => windows_arguments,
        };
    }

    windows_arguments
}

fn convert_var<'a>(value: &'a str, buffer: &mut Vec<&'a str>) {
    // Batch file vars have one of two forms: `%NAME%` (corresponding to regular variables),
    // or `%n` if `n` is a digit in the range 0 to 9 or an `*` (corresponding to input params).
    match value {
        "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" => {
            buffer.push("%");
            buffer.push(value);
        }
        "@" => buffer.push("%*"),
        _ => {
            buffer.push("%");
            buffer.push(value);
            buffer.push("%");
        }
    }
}

fn replace_full_vars(arguments: &str) -> String {
    let mut parts: Vec<&str> = arguments.split("${").collect();
    let mut buffer = vec![];

    buffer.push(parts.remove(0));

    for part in parts {
        let (before, after, found) = match part.find("}") {
            None => (part, "", false),
            Some(index) => {
                let values = part.split_at(index);

                (values.0, &values.1[1..values.1.len()], true)
            }
        };

        if found {
            convert_var(before, &mut buffer);
        } else {
            buffer.push(before)
        }

        if after.len() > 0 {
            buffer.push(after);
        }
    }

    buffer.join("").to_string()
}

fn replace_partial_vars(arguments: &str) -> String {
    let mut parts: Vec<&str> = arguments.split('$').collect();
    let mut buffer = vec![];

    buffer.push(parts.remove(0));

    for part in parts {
        let (before, after) = match part.find(" ") {
            None => (part, ""),
            Some(index) => part.split_at(index),
        };

        convert_var(before, &mut buffer);

        if after.len() > 0 {
            buffer.push(after);
        }
    }

    buffer.join("").to_string()
}

fn replace_vars(arguments: &str) -> String {
    let mut updated_arguments = replace_full_vars(arguments);
    updated_arguments = replace_partial_vars(&updated_arguments);

    updated_arguments
}

fn add_arguments(arguments: &str, additional_arguments: Vec<(&str)>) -> String {
    let mut windows_arguments = arguments.clone().to_string();

    for additional_argument in additional_arguments {
        windows_arguments.push_str(additional_argument);
    }

    windows_arguments.to_string()
}

fn convert_line(line: &str) -> String {
    if line.contains(SHELL2BATCH_PREFIX) {
        let index = line.find(SHELL2BATCH_PREFIX).unwrap() + SHELL2BATCH_PREFIX.len();
        let windows_command = line[index..].trim();
        windows_command.to_string()
    } else if line.starts_with("#") {
        let mut windows_command = String::from(line);
        windows_command.remove(0);
        windows_command.insert_str(0, "@REM ");

        windows_command
    } else {
        // assume first word is the command
        let (shell_command, mut arguments) = match line.find(" ") {
            None => (line, "".to_string()),
            Some(index) => {
                let (shell_command, arguments_str) = line.split_at(index);

                (shell_command, arguments_str.to_string())
            }
        };

        arguments = arguments.trim().to_string();

        let (mut windows_command, flags_mappings, additional_arguments, modify_path_separator) =
            match shell_command {
                "cp" => {
                    // There is no good `cp` equivalent on windows. There are
                    // two tools we can rely on:
                    //
                    // - xcopy, which is great for directory to directory
                    //   copies.
                    // - copy, which is great for file to file/directory copies.
                    //
                    // We can select which one to use based on the presence of
                    // the -r flag.
                    let win_cmd = match Regex::new("(^|\\s)-[^ ]*[rR]") {
                        Ok(regex_instance) => {
                            if regex_instance.is_match(&arguments) {
                                "xcopy".to_string()
                            } else {
                                "copy".to_string()
                            }
                        }
                        Err(_) => "copy".to_string(),
                    };

                    let flags_mappings = if win_cmd == "xcopy".to_string() {
                        vec![("-[rR]", "/E")]
                    } else {
                        vec![]
                    };
                    (win_cmd, flags_mappings, vec![], true)
                }
                "mv" => ("move".to_string(), vec![], vec![], true),
                "ls" => ("dir".to_string(), vec![], vec![], true),
                "rm" => {
                    let win_cmd = match Regex::new("-[^ ]*[rR]") {
                        Ok(regex_instance) => {
                            if regex_instance.is_match(&arguments) {
                                "rmdir".to_string()
                            } else {
                                "del".to_string()
                            }
                        }
                        Err(_) => "del".to_string(),
                    };

                    let flags_mappings = if win_cmd == "rmdir".to_string() {
                        vec![("-([rR][fF]|[fF][rR]) ", "/S /Q "), ("-[rR]+ ", "/S ")]
                    } else {
                        vec![("-[fF] ", "/Q ")]
                    };

                    (win_cmd, flags_mappings, vec![], true)
                }
                "mkdir" => ("mkdir".to_string(), vec![("-[pP]", "")], vec![], true),
                "clear" => ("cls".to_string(), vec![], vec![], false),
                "grep" => ("find".to_string(), vec![], vec![], false),
                "pwd" => ("chdir".to_string(), vec![], vec![], false),
                "export" => ("set".to_string(), vec![], vec![], false),
                "unset" => ("set".to_string(), vec![], vec!["="], false),
                _ => (shell_command.to_string(), vec![], vec![], false),
            };

        // modify paths
        if modify_path_separator {
            arguments = arguments.replace("/", "\\");
        }

        // replace flags
        let mut windows_arguments = if flags_mappings.len() > 0 {
            replace_flags(&arguments, flags_mappings)
        } else {
            arguments.to_string()
        };

        // replace vars
        windows_arguments = if windows_arguments.len() > 0 {
            replace_vars(&windows_arguments)
        } else {
            windows_arguments
        };

        // add additional arguments
        windows_arguments = if additional_arguments.len() > 0 {
            add_arguments(&windows_arguments, additional_arguments)
        } else {
            windows_arguments
        };

        if windows_arguments.len() > 0 {
            windows_command.push_str(" ");
            windows_command.push_str(&windows_arguments);
        }

        windows_command
    }
}

/// Converts the provided shell script and returns the windows batch script text.
pub(crate) fn run(script: &str) -> String {
    let lines: Vec<&str> = script.split('\n').collect();
    let mut windows_batch = vec![];

    for mut line in lines {
        line = line.trim();
        let mut line_string = line.to_string();

        // convert line
        let converted_line = if line_string.len() == 0 {
            line_string
        } else {
            convert_line(&mut line_string)
        };

        windows_batch.push(converted_line);
    }

    windows_batch.join("\n")
}