//! Utility helpers inlined from `zesdex-utils` — safe integer casts,
//! atomic JSON file writing, and slugification.
//!
//! # Inlining rationale
//!
//! These helpers are ported from `zesdex-utils` to avoid a hard
//! dependency on that crate during the clean-architecture migration.
//! Once `zesdex-utils` is fully migrated, these can be re-exported
//! or removed.

use serde::Serialize;
use std::io::Write;
use std::path::Path;

// ---------------------------------------------------------------------------
// CastOr — safe integer narrowing
// ---------------------------------------------------------------------------

/// Extension trait for checked integer narrowing with a fallback default.
///
/// Implementations use `U::try_from(self).unwrap_or(default)` so overflow
/// never panics.
pub trait CastOr<U> {
    fn cast_or(self, default: U) -> U;
}

macro_rules! impl_cast_or {
    ($from:ty => $($to:ty),+ $(,)?) => {
        $(
            impl CastOr<$to> for $from {
                #[inline]
                fn cast_or(self, default: $to) -> $to {
                    <$to as TryFrom<$from>>::try_from(self).unwrap_or(default)
                }
            }
        )+
    };
}

impl_cast_or!(usize => u64, i64, u32, i32, u16);
impl_cast_or!(u64 => i64, u32, i32, u16, u8);
impl_cast_or!(i64 => u64, i32, u16, u8);
impl_cast_or!(u32 => i32, u16, u8);

impl CastOr<u64> for u128 {
    #[inline]
    fn cast_or(self, default: u64) -> u64 {
        u64::try_from(self).unwrap_or(default)
    }
}

impl CastOr<i64> for u128 {
    #[inline]
    fn cast_or(self, default: i64) -> i64 {
        i64::try_from(self).unwrap_or(default)
    }
}

impl CastOr<u32> for u128 {
    #[inline]
    fn cast_or(self, default: u32) -> u32 {
        u32::try_from(self).unwrap_or(default)
    }
}

// ---------------------------------------------------------------------------
// Atomic JSON write
// ---------------------------------------------------------------------------

/// Atomically write serializable `data` to `path`.
///
/// Flow: serialize to pretty JSON -> write to `path.tmp` -> fsync -> rename
/// -> fsync parent. If `mode` is `Some`, set permissions before rename (Unix only).
pub fn write_json_atomic<T: Serialize>(path: &Path, data: &T, mode: Option<u32>) -> std::io::Result<()> {
    let tmp = path.with_extension("tmp");
    let bytes = serde_json::to_vec_pretty(data)
        .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
    {
        let mut f = std::fs::OpenOptions::new()
            .create(true)
            .truncate(true)
            .write(true)
            .open(&tmp)?;
        f.write_all(&bytes)?;
        f.sync_all()?;
    }
    if let Some(m) = mode {
        #[cfg(unix)]
        {
            use std::os::unix::fs::PermissionsExt;
            std::fs::set_permissions(&tmp, std::fs::Permissions::from_mode(m))?;
        }
        #[cfg(not(unix))]
        { let _ = m; }
    }
    std::fs::rename(&tmp, path)?;
    if let Some(parent) = path.parent() {
        let _ = std::fs::File::open(parent).and_then(|d| d.sync_all());
    }
    Ok(())
}

// ---------------------------------------------------------------------------
// Slugify
// ---------------------------------------------------------------------------

/// Convert an arbitrary string into a filesystem-safe slug.
pub fn slugify(s: &str) -> Option<String> {
    let slug: String = s
        .to_lowercase()
        .chars()
        .map(|c| if c.is_ascii_alphanumeric() { c } else { '-' })
        .collect();
    let slug: String = slug
        .split('-')
        .filter(|s| !s.is_empty())
        .collect::<Vec<_>>()
        .join("-");
    if slug.is_empty() || slug.len() > 80 {
        return None;
    }
    Some(slug)
}

// ---------------------------------------------------------------------------
// Clipboard (OSC-52)
// ---------------------------------------------------------------------------

/// Write `text` to the terminal's clipboard using the OSC-52 escape sequence.
///
/// OSC-52 (`\x1b]52;c;<base64>\x1b\\`) is supported by many terminal emulators
/// (iTerm2, Kitty, tmux, etc.) and allows writing to the system clipboard
/// without external binaries.
pub fn write_osc52(output: &mut impl Write, text: &str) -> std::io::Result<()> {
    use base64::Engine as _;
    let encoded = base64::engine::general_purpose::STANDARD.encode(text.as_bytes());
    write!(output, "\x1b]52;c;{encoded}\x1b\\")?;
    output.flush()?;
    Ok(())
}