//! Durable context reference records and media attachment parsing.
//!
//! Separated from composer completion and terminal-only UI so session persistence,
//! image attachment, and engine history can reference context and attachment items
//! without depending on `codewhale-tui`.

use serde::{Deserialize, Serialize};

/// The transcript keeps the user's compact text (`@path` or `[Attached ...]`)
/// readable. This record preserves the exact target and inclusion state for
/// the context inspector and for session resume without leaking raw metadata
/// into the visible history cell.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ContextReference {
    pub kind: ContextReferenceKind,
    pub source: ContextReferenceSource,
    /// Short badge for terminal display, e.g. `file`, `dir`, `image`.
    pub badge: String,
    /// Compact display label from the transcript, without the leading `@`.
    pub label: String,
    /// Resolved target path or URI-equivalent string.
    pub target: String,
    pub included: bool,
    pub expanded: bool,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub detail: Option<String>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ContextReferenceKind {
    File,
    Directory,
    Missing,
    Unsupported,
    MediaMention,
    MediaAttachment,
    /// `@git` / `@diff` — curated git context rather than a path (#4067).
    GitContext,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ContextReferenceSource {
    AtMention,
    Attachment,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct MediaAttachmentReference {
    pub kind: String,
    pub path: String,
    pub start_byte: usize,
    pub end_byte: usize,
}

/// Extract media attachment references from text formatted as `[Attached <kind>: <path>]`.
#[must_use]
pub fn media_attachment_references(input: &str) -> Vec<MediaAttachmentReference> {
    let mut out = Vec::new();
    let mut offset = 0usize;
    for line in input.split_inclusive('\n') {
        let start_byte = offset;
        let end_byte = offset + line.len();
        offset = end_byte;
        let trimmed = line.trim();
        let Some(body) = trimmed
            .strip_prefix("[Attached ")
            .and_then(|value| value.strip_suffix(']'))
        else {
            continue;
        };
        let Some((kind, rest)) = body.split_once(": ") else {
            continue;
        };
        let path = attachment_path(rest).trim();
        if !path.is_empty() {
            out.push(MediaAttachmentReference {
                kind: kind.trim().to_string(),
                path: path.to_string(),
                start_byte,
                end_byte,
            });
        }
    }
    out
}

/// The path in `<description> at <path>` or a bare `<path>`. Attachment
/// producers write absolute paths, and a description never starts with one,
/// so the separator is the first ` at ` followed by an absolute path.
/// Splitting at the last ` at ` broke paths that contain one, such as macOS
/// screenshot names (`Screenshot 2026-09-28 at 9.18.11 AM.png`). Text with no
/// absolute candidate (hand-written or older sessions) keeps the last-` at `
/// split it always had.
fn attachment_path(rest: &str) -> &str {
    if looks_absolute(rest) {
        return rest;
    }
    rest.match_indices(" at ")
        .map(|(idx, sep)| &rest[idx + sep.len()..])
        .find(|candidate| looks_absolute(candidate))
        .or_else(|| rest.rsplit_once(" at ").map(|(_, path)| path))
        .unwrap_or(rest)
}

fn looks_absolute(path: &str) -> bool {
    let bytes = path.as_bytes();
    path.starts_with(['/', '\\', '~'])
        || (bytes.len() >= 3
            && bytes[0].is_ascii_alphabetic()
            && bytes[1] == b':'
            && matches!(bytes[2], b'\\' | b'/'))
}

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

    #[test]
    fn serialization_roundtrip() {
        let reference = ContextReference {
            kind: ContextReferenceKind::File,
            source: ContextReferenceSource::AtMention,
            badge: "file".to_string(),
            label: "test.rs".to_string(),
            target: "/path/to/test.rs".to_string(),
            included: true,
            expanded: false,
            detail: Some("included".to_string()),
        };
        let json = serde_json::to_string(&reference).unwrap();
        let deserialized: ContextReference = serde_json::from_str(&json).unwrap();
        assert_eq!(reference, deserialized);
    }

    #[test]
    fn parses_media_attachments() {
        let input = "Here is the screenshot:\n[Attached image: 100x100 at /tmp/shot.png]\nPlease analyze it.";
        let refs = media_attachment_references(input);
        assert_eq!(refs.len(), 1);
        assert_eq!(refs[0].kind, "image");
        assert_eq!(refs[0].path, "/tmp/shot.png");
    }

    #[test]
    fn attachment_paths_may_contain_at() {
        let shot = "/Users/x/Desktop/Screenshot 2026-09-28 at 9.18.11 AM.png";
        let bare = format!("[Attached image: {shot}]");
        assert_eq!(media_attachment_references(&bare)[0].path, shot);
        let described = format!("[Attached image: 8x4 PNG (2KB) at {shot}]");
        assert_eq!(media_attachment_references(&described)[0].path, shot);
        let windows = r"[Attached image: 8x4 PNG at C:\Users\x\Shot at noon.png]";
        assert_eq!(
            media_attachment_references(windows)[0].path,
            r"C:\Users\x\Shot at noon.png"
        );
        let relative = "[Attached image: 8x4 PNG at shots/a.png]";
        assert_eq!(media_attachment_references(relative)[0].path, "shots/a.png");
    }
}