use regex::Regex;
use serde::{Deserialize, Serialize};

use crate::{NominaError, RenameContext, RenameRule};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RegexRule {
    pub pattern: String,
    pub replace_with: String,
    pub case_insensitive: bool,
    pub enabled: bool,
}

impl RegexRule {
    pub fn new() -> Self {
        Self {
            pattern: String::new(),
            replace_with: String::new(),
            case_insensitive: false,
            enabled: true,
        }
    }

    fn build_regex(&self) -> std::result::Result<Regex, NominaError> {
        let pat = if self.case_insensitive {
            format!("(?i){}", self.pattern)
        } else {
            self.pattern.clone()
        };
        Regex::new(&pat).map_err(|e| NominaError::InvalidRegex {
            pattern: self.pattern.clone(),
            reason: e.to_string(),
        })
    }
}

impl RenameRule for RegexRule {
    fn apply(&self, filename: &str, _context: &RenameContext) -> String {
        if self.pattern.is_empty() {
            return filename.to_string();
        }
        match self.build_regex() {
            Ok(re) => re.replace_all(filename, self.replace_with.as_str()).into_owned(),
            Err(_) => filename.to_string(),
        }
    }

    fn display_name(&self) -> &str {
        "Regex"
    }

    fn rule_type(&self) -> &str {
        "regex"
    }

    fn is_enabled(&self) -> bool {
        self.enabled
    }
}

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

    #[test]
    fn basic_regex() {
        let rule = RegexRule {
            pattern: r"(\d+)".into(),
            replace_with: "NUM".into(),
            case_insensitive: false,
            enabled: true,
        };
        let ctx = RenameContext::dummy(0);
        assert_eq!(rule.apply("file123", &ctx), "fileNUM");
    }

    #[test]
    fn capture_groups() {
        let rule = RegexRule {
            pattern: r"([a-z]+)-([a-z]+)".into(),
            replace_with: "${2}_${1}".into(),
            case_insensitive: false,
            enabled: true,
        };
        let ctx = RenameContext::dummy(0);
        assert_eq!(rule.apply("hello-world", &ctx), "world_hello");
    }

    #[test]
    fn empty_pattern() {
        let rule = RegexRule {
            pattern: String::new(),
            replace_with: "x".into(),
            case_insensitive: false,
            enabled: true,
        };
        let ctx = RenameContext::dummy(0);
        assert_eq!(rule.apply("test", &ctx), "test");
    }
}