use serde::{Deserialize, Serialize};
use sha2::Digest;

use crate::{RenameContext, RenameRule};

#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq)]
pub enum HashMode {
    #[default]
    None,
    Prefix,
    Suffix,
    Replace,
}

#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq)]
pub enum HashAlgorithm {
    MD5,
    SHA1,
    #[default]
    SHA256,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HashRule {
    pub mode: HashMode,
    pub algorithm: HashAlgorithm,
    pub length: usize,
    pub separator: String,
    pub uppercase: bool,
    pub enabled: bool,
}

impl HashRule {
    pub fn new() -> Self {
        Self {
            mode: HashMode::None,
            algorithm: HashAlgorithm::SHA256,
            length: 0,
            separator: "_".into(),
            uppercase: false,
            enabled: true,
        }
    }

    fn compute_hash(&self, data: &[u8]) -> String {
        let raw = match self.algorithm {
            HashAlgorithm::MD5 => {
                let mut h = md5::Md5::new();
                h.update(data);
                format!("{:x}", h.finalize())
            }
            HashAlgorithm::SHA1 => {
                let mut h = sha1::Sha1::new();
                h.update(data);
                format!("{:x}", h.finalize())
            }
            HashAlgorithm::SHA256 => {
                let mut h = sha2::Sha256::new();
                h.update(data);
                format!("{:x}", h.finalize())
            }
        };

        let truncated = if self.length > 0 && self.length < raw.len() {
            &raw[..self.length]
        } else {
            &raw
        };

        if self.uppercase {
            truncated.to_uppercase()
        } else {
            truncated.to_string()
        }
    }
}

impl RenameRule for HashRule {
    fn apply(&self, filename: &str, context: &RenameContext) -> String {
        if self.mode == HashMode::None {
            return filename.to_string();
        }

        let data = match std::fs::read(&context.path) {
            Ok(d) => d,
            Err(_) => return filename.to_string(),
        };

        let hash = self.compute_hash(&data);

        match self.mode {
            HashMode::None => filename.to_string(),
            HashMode::Prefix => format!("{}{}{}", hash, self.separator, filename),
            HashMode::Suffix => format!("{}{}{}", filename, self.separator, hash),
            HashMode::Replace => hash,
        }
    }

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

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

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

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

    #[test]
    fn mode_none_returns_unchanged() {
        let rule = HashRule::new();
        let ctx = RenameContext::dummy(0);
        assert_eq!(rule.apply("photo.jpg", &ctx), "photo.jpg");
    }

    #[test]
    fn file_read_fails_returns_unchanged() {
        let mut rule = HashRule::new();
        rule.mode = HashMode::Prefix;
        let ctx = RenameContext::dummy(0);
        // dummy context points to a nonexistent file, so read fails
        assert_eq!(rule.apply("photo.jpg", &ctx), "photo.jpg");
    }

    #[test]
    fn suffix_mode_read_fail_unchanged() {
        let mut rule = HashRule::new();
        rule.mode = HashMode::Suffix;
        rule.algorithm = HashAlgorithm::MD5;
        rule.length = 8;
        rule.uppercase = true;
        let ctx = RenameContext::dummy(0);
        assert_eq!(rule.apply("doc.pdf", &ctx), "doc.pdf");
    }
}