//! Fixed preview geometry. These are deliberately constants instead of config:
//! the preview is a product decision (what a list view loads), not a per-host
//! tuning knob, and every deployment must produce identical derivatives for the
//! same upload.

/// Longest-edge ceiling for full-content images (chat pictures, banners).
pub const CONTENT_MAX_EDGE: u32 = 1920;
/// Longest-edge ceiling for avatar-shaped images.
pub const AVATAR_MAX_EDGE: u32 = 512;
/// JPEG quality for the opaque preview encoding.
pub const JPEG_QUALITY: u8 = 82;
/// Sources above this size are served as-is instead of being decoded.
pub const MAX_SOURCE_BYTES: u64 = 32 * 1024 * 1024;
/// Decoded pixel ceiling; guards against decompression bombs.
pub const MAX_DECODE_PIXELS: u64 = 40_000_000;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PreviewPreset {
    /// Small, square-ish target for avatars and space avatars.
    Avatar,
    /// General picture target for chat attachments and space banners.
    Content,
}

impl PreviewPreset {
    #[must_use]
    pub fn max_edge(self) -> u32 {
        match self {
            Self::Avatar => AVATAR_MAX_EDGE,
            Self::Content => CONTENT_MAX_EDGE,
        }
    }

    #[must_use]
    pub fn jpeg_quality(self) -> u8 {
        JPEG_QUALITY
    }

    #[must_use]
    pub fn max_source_bytes(self) -> u64 {
        MAX_SOURCE_BYTES
    }

    #[must_use]
    pub fn max_decode_pixels(self) -> u64 {
        MAX_DECODE_PIXELS
    }

    /// Whether a source alpha channel must survive into the preview. Avatars and
    /// pictures can both be cut-outs, so both keep it.
    #[must_use]
    pub fn keep_alpha(self) -> bool {
        true
    }
}