use std::collections::HashSet;
use std::path::{Path, PathBuf};

use uuid::Uuid;

use crate::config::SharedRepoConfig;
use crate::error::{RepoError, RepoResult};

pub const DEFAULT_OBJECT_FORMAT_SHA1: &str = "sha1";
pub const DEFAULT_OBJECT_FORMAT_SHA256: &str = "sha256";

pub fn validate_repo_name(name: &str, max_len: usize) -> RepoResult<String> {
    let trimmed = name.trim();
    if trimmed.is_empty() {
        return Err(RepoError::BadRequest("repository name is empty".into()));
    }
    if trimmed.len() > max_len {
        return Err(RepoError::BadRequest(format!(
            "repository name too long (max {max_len})"
        )));
    }
    if !trimmed
        .chars()
        .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '-'))
    {
        return Err(RepoError::BadRequest(
            "repository name must match [A-Za-z0-9._-]".into(),
        ));
    }
    if trimmed.starts_with('.') || trimmed.starts_with('-') {
        return Err(RepoError::BadRequest(
            "repository name may not start with '.' or '-'".into(),
        ));
    }
    Ok(trimmed.to_lowercase())
}

pub fn validate_branch_name(name: &str, max_len: usize) -> RepoResult<String> {
    let trimmed = name.trim();
    if trimmed.is_empty() || trimmed.len() > max_len {
        return Err(RepoError::BadRequest("invalid branch name".into()));
    }
    if trimmed.starts_with('-') || trimmed.starts_with('.') {
        return Err(RepoError::BadRequest("invalid branch name prefix".into()));
    }
    if trimmed.contains("..") || trimmed.contains("@{") || trimmed.contains('\\') {
        return Err(RepoError::BadRequest("invalid branch name".into()));
    }
    Ok(trimmed.to_string())
}

pub fn validate_tag_name(name: &str, max_len: usize) -> RepoResult<String> {
    let trimmed = name.trim();
    if trimmed.is_empty() || trimmed.len() > max_len {
        return Err(RepoError::BadRequest("invalid tag name".into()));
    }
    if trimmed.contains("..") || trimmed.contains(' ') {
        return Err(RepoError::BadRequest("invalid tag name".into()));
    }
    Ok(trimmed.to_string())
}

pub fn validate_object_format(fmt: &str) -> RepoResult<&'static str> {
    match fmt {
        "sha1" => Ok(DEFAULT_OBJECT_FORMAT_SHA1),
        "sha256" => Ok(DEFAULT_OBJECT_FORMAT_SHA256),
        _ => Err(RepoError::BadRequest(format!(
            "unsupported object format: {fmt}"
        ))),
    }
}

pub fn git_bare_path(config: &SharedRepoConfig, channel_id: Uuid, repo_id: Uuid) -> PathBuf {
    Path::new(&config.git_storage_root)
        .join(channel_id.to_string())
        .join(format!("{repo_id}.git"))
}

pub fn lfs_path(config: &SharedRepoConfig, channel_id: Uuid, repo_id: Uuid) -> PathBuf {
    Path::new(&config.lfs_storage_root)
        .join(channel_id.to_string())
        .join(repo_id.to_string())
}

pub fn parse_owner_repo_slug(slug: &str) -> RepoResult<(&str, &str)> {
    let (space, repo) = slug
        .split_once('/')
        .ok_or_else(|| RepoError::BadRequest("expected '<space_name>/<repo_name>'".into()))?;
    if space.is_empty() || repo.is_empty() {
        return Err(RepoError::BadRequest("empty space or repo segment".into()));
    }
    Ok((space, repo))
}

pub fn normalize_topic(topic: &str) -> RepoResult<String> {
    let t = topic.trim().to_lowercase();
    if t.is_empty() {
        return Err(RepoError::BadRequest("empty topic".into()));
    }
    if t.len() > 35 {
        return Err(RepoError::BadRequest("topic too long".into()));
    }
    if !t
        .chars()
        .all(|c| c.is_ascii_alphanumeric() || matches!(c, '-' | '_' | '.'))
    {
        return Err(RepoError::BadRequest("invalid topic characters".into()));
    }
    Ok(t)
}

pub fn sanitize_topics<I, S>(topics: I, max: usize) -> RepoResult<Vec<String>>
where
    I: IntoIterator<Item = S>,
    S: AsRef<str>,
{
    let mut seen = HashSet::new();
    let mut out = Vec::new();
    for t in topics {
        let n = normalize_topic(t.as_ref())?;
        if seen.insert(n.clone()) {
            out.push(n);
        }
    }
    if out.len() > max {
        return Err(RepoError::BadRequest(format!(
            "too many topics (max {max})"
        )));
    }
    Ok(out)
}