//! impeccable-bundle: the page JS and the bundler behind `cargo xtask bundle`.
//!
//! Every browser artifact the detector ships is this crate's output: the
//! in-page bundle (`dist/detect-antipatterns-browser.js`, also the tracked
//! `crates/live/assets/` copy the engine embeds and serves as `/detect.js`)
//! and the five `extension/detector/` pieces. The page JS is embedded with
//! `include_str!`, so a crate that depends on this one gets it without
//! copying `browser-bundle/*.js` anywhere.
//!
//! A downstream crate that links `impeccable-core` + `impeccable-wasm` plus
//! its own [`RulePack`](impeccable_core::rule_pack::RulePack) into one wasm
//! module builds the same artifacts for its own module:
//!
//! ```no_run
//! use std::path::Path;
//! let (glue, wasm) = impeccable_bundle::wasm_pack_build(
//!     Path::new("crates/my-wasm"),
//!     Path::new("target/wasm-bundle"),
//!     &[],
//! )?;
//! let js = impeccable_bundle::in_page_bundle(&glue, &wasm);
//! let registry = impeccable_bundle::registry_json();
//! let ext = impeccable_bundle::extension_pieces(&glue, &wasm, &registry);
//! # Ok::<(), String>(())
//! ```
//!
//! The pack's rows reach [`registry_json`] once the pack is installed
//! (`impeccable_core::rule_pack::install`), because the registry reads
//! built-ins plus every registered slice.
//!
//! Nothing here writes files or exits the process: the caller decides where
//! the bytes go and how a failure is reported.

use base64::Engine as _;
use std::borrow::Cow;
use std::path::{Path, PathBuf};
use std::process::Command;

macro_rules! page_js {
    ($($name:literal),* $(,)?) => {
        /// The page JS, in the order [`in_page_bundle`] concatenates it:
        /// `(file name, source)`. Embedded at compile time from
        /// `browser-bundle/`.
        pub const PAGE_JS: &[(&str, &str)] = &[
            $(($name, include_str!(concat!("../../../browser-bundle/", $name))),)*
        ];
    };
}

page_js![
    "00-header.js",
    "10-probe.js",
    "15-snapshot.js",
    "30-scan-common.js",
    "35-visual.js",
    "40-overlay.js",
    "50-scan.js",
    "60-offscreen.js",
    "99-footer.js",
];

/// One embedded page file by name.
pub fn page_js(name: &str) -> Option<&'static str> {
    PAGE_JS.iter().find(|(n, _)| *n == name).map(|(_, src)| *src)
}

fn src(name: &str) -> Cow<'static, str> {
    let s = page_js(name).unwrap_or_else(|| panic!("browser-bundle/{name}: not embedded"));
    if s.ends_with('\n') {
        Cow::Borrowed(s)
    } else {
        Cow::Owned(format!("{s}\n"))
    }
}

/// In-page bundle concatenation order. `@@GLUE@@` is the wasm-bindgen glue,
/// `@@WASM@@` the embedded module + synchronous instantiation.
const ORDER: &[&str] = &[
    "00-header.js",
    "10-probe.js",
    "15-snapshot.js",
    "@@GLUE@@",
    "@@WASM@@",
    "30-scan-common.js",
    "35-visual.js",
    "40-overlay.js",
    "50-scan.js",
    "99-footer.js",
];

/// The extension pieces, each an IIFE over a subset of the same sources plus
/// a `window.*` export line. `core.js` is the wasm glue + an async loader
/// (the module ships beside it as `core_bg.wasm`; no base64: the offscreen
/// document fetches it) + the scan plumbing and visual-contrast orchestration
/// + the offscreen session protocol.
const EXT_SNAPSHOT: &[&str] = &["15-snapshot.js"];
const EXT_OVERLAY: &[&str] = &["40-overlay.js"];
const EXT_CORE: &[&str] = &["@@GLUE@@", "@@LOADER@@", "30-scan-common.js", "35-visual.js", "60-offscreen.js"];

fn push_glue(out: &mut String, glue_js: &str) {
    out.push_str("// --- wasm-bindgen glue (generated by cargo xtask bundle) ---\n");
    out.push_str(glue_js);
    if !glue_js.ends_with('\n') {
        out.push('\n');
    }
}

/// The in-page bundle: `dist/detect-antipatterns-browser.js` and the tracked
/// `crates/live/assets/` copy. `glue_js` and `wasm` are one wasm-pack
/// `--target no-modules` build (see [`wasm_pack_build`]); the module is
/// embedded as base64 and instantiated synchronously at load.
///
/// Deterministic: the same glue and module produce the same bytes.
pub fn in_page_bundle(glue_js: &str, wasm: &[u8]) -> String {
    let b64 = base64::engine::general_purpose::STANDARD.encode(wasm);
    let mut out = String::new();
    for part in ORDER {
        match *part {
            "@@GLUE@@" => push_glue(&mut out, glue_js),
            "@@WASM@@" => {
                out.push_str("// --- impeccable_wasm module (generated by cargo xtask bundle) ---\n");
                out.push_str(&format!("const __IMPECCABLE_WASM_BYTES = {};\n", wasm.len()));
                out.push_str("const __IMPECCABLE_WASM_B64 = \"");
                out.push_str(&b64);
                out.push_str("\";\n");
                out.push_str(WASM_INIT);
            }
            name => out.push_str(&src(name)),
        }
    }
    out
}

/// What goes into `extension/detector/`, from [`extension_pieces`].
pub struct ExtensionPieces {
    /// `snapshot.js`: the content-script page snapshot producer.
    pub snapshot_js: String,
    /// `overlay.js`: the content-script overlay UI.
    pub overlay_js: String,
    /// `core.js`: the offscreen-document wasm loader and scan session.
    pub core_js: String,
    /// `core_bg.wasm`: the module `core.js` fetches beside itself.
    pub core_bg_wasm: Vec<u8>,
    /// `antipatterns.json`: the registry slice the extension panel reads.
    pub antipatterns_json: String,
}

/// The extension pieces for one wasm build. `registry_json` is written
/// through unchanged, so a caller can pass [`registry_json()`] or its own.
pub fn extension_pieces(glue_js: &str, wasm: &[u8], registry_json: &str) -> ExtensionPieces {
    let piece = |parts: &[&str], exports: &str, what: &str| -> String {
        let mut p = format!(
            "/**\n * Impeccable extension: {what}\n * Copyright (c) 2026 Paul Bakaus\n *\n * GENERATED -- do not edit. Source: browser-bundle/*.js (+ crates/core, crates/wasm for core.js).\n * Rebuild: cargo xtask bundle\n */\n"
        );
        p.push_str("(function () {\n");
        for part in parts {
            match *part {
                "@@GLUE@@" => push_glue(&mut p, glue_js),
                "@@LOADER@@" => p.push_str(EXT_CORE_LOADER),
                name => p.push_str(&src(name)),
            }
        }
        p.push_str(exports);
        p.push_str("})();\n");
        p
    };
    ExtensionPieces {
        snapshot_js: piece(
            EXT_SNAPSHOT,
            "window.__impeccableSnapshot = __impeccableSnapshot;\nwindow.__impeccableCreateDrawableIO = __createDrawableIO;\n",
            "snapshot.js, the content-script page snapshot producer (measurement only)",
        ),
        overlay_js: piece(
            EXT_OVERLAY,
            "window.__impeccableCreateOverlay = createImpeccableOverlay;\n",
            "overlay.js, the content-script overlay UI (draws a findings list; no rules)",
        ),
        core_js: piece(
            EXT_CORE,
            "",
            "core.js, the offscreen-document WASM core loader + scan session (rules run in core_bg.wasm)",
        ),
        core_bg_wasm: wasm.to_vec(),
        antipatterns_json: registry_json.to_string(),
    }
}

/// The `atob` + synchronous instantiation that runs at bundle load. Chrome
/// (verified on 151, headless and headed) compiles multi-MB modules
/// synchronously on the main thread; the historical 4 KB limit no longer
/// applies to `new WebAssembly.Module`. A CSP without 'wasm-unsafe-eval'
/// throws here; consumers handle that per docs/WASM-BUNDLE.md.
const WASM_INIT: &str = r#"function __impeccableWasmBytes() {
  const bin = atob(__IMPECCABLE_WASM_B64);
  const bytes = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) bytes[i] = bin.charCodeAt(i);
  return bytes;
}
let __impeccable = null;
let __impeccableInitError = null;
try {
  wasm_bindgen.initSync({ module: __impeccableWasmBytes() });
  __impeccable = wasm_bindgen;
} catch (e) {
  __impeccableInitError = e;
}
"#;

/// The offscreen document's core loader: fetch the module beside the script
/// and instantiate asynchronously (the extension's own CSP carries
/// 'wasm-unsafe-eval'). Also stubs the live-page probe namespace the glue
/// imports, so a call that would need a page fails loudly instead of with a
/// ReferenceError.
const EXT_CORE_LOADER: &str = r#"const __impeccableDom = new Proxy({}, {
  get() { throw new Error('[impeccable] the offscreen document has no live page; load a snapshot first'); },
});
async function __impeccableLoadCore() {
  await wasm_bindgen({ module_or_path: chrome.runtime.getURL('detector/core_bg.wasm') });
  return wasm_bindgen;
}
"#;

/// The capture contract: the property and state lists in `15-snapshot.js`
/// must equal the core's (`STYLE_PROPS`, `PSEUDO_PROPS` in snapshot.rs;
/// `STATE_PSEUDOS` in selector.rs), or a rule reads a column the capture did
/// not write. Returns the mismatch report on drift.
pub fn check_capture_contract() -> Result<(), String> {
    let snapshot_js = page_js("15-snapshot.js").expect("15-snapshot.js embedded");
    fn js_list(src: &str, name: &str) -> Vec<String> {
        let start = src
            .find(&format!("const {name} = ["))
            .unwrap_or_else(|| panic!("15-snapshot.js: {name} not found"));
        let rest = &src[start..];
        let end = rest.find("];").expect("list end");
        rest[..end]
            .split('"')
            .skip(1)
            .step_by(2)
            .map(|s| s.to_string())
            .collect()
    }
    let pairs: [(&str, Vec<String>); 3] = [
        ("__SNAP_STYLE_PROPS", impeccable_core::browser::snapshot::STYLE_PROPS.iter().map(|s| s.to_string()).collect()),
        ("__SNAP_PSEUDO_PROPS", impeccable_core::browser::snapshot::PSEUDO_PROPS.iter().map(|s| s.to_string()).collect()),
        ("__SNAP_STATE_PSEUDOS", impeccable_core::browser::selector::STATE_PSEUDOS.iter().map(|s| s.to_string()).collect()),
    ];
    for (name, want) in pairs {
        let have = js_list(snapshot_js, name);
        if have != want {
            return Err(format!(
                "browser-bundle/15-snapshot.js {name} differs from the core's list\n  js:   {have:?}\n  core: {want:?}"
            ));
        }
    }
    Ok(())
}

/// `antipatterns.json`: `{ id, name, category, description }` per rule, in
/// registry order (built-ins first, then any installed rule pack's rows), as
/// 2-space JSON with a trailing newline. This is the shape `bun run build`
/// and the extension panel read.
pub fn registry_json() -> String {
    let rows: Vec<serde_json::Value> = impeccable_core::registry::all_antipatterns()
        .map(|ap| {
            serde_json::json!({
                "id": ap.id,
                "name": ap.name,
                "category": ap.category,
                "description": ap.description,
            })
        })
        .collect();
    let mut s = serde_json::to_string_pretty(&rows).expect("registry json");
    s.push('\n');
    s
}

/// Build the wasm module for `crate_dir` and read back the wasm-bindgen glue
/// and the `.wasm`:
///
/// ```text
/// wasm-pack build <crate_dir> --target no-modules --release \
///   --no-typescript --no-pack --out-dir <out_dir> --out-name impeccable
/// ```
///
/// `extra_cargo_args` are passed to cargo after `--` (the workspace uses this
/// for `--features pure-exports`). `WASM_PACK` names the binary when it is
/// not on PATH; `IMPECCABLE_BUNDLE_SKIP_WASM_PACK=1` (or the older
/// `IMPECCABLE_XTASK_SKIP_WASM_PACK=1`) reuses whatever `out_dir` already
/// holds, for iterating on the page JS alone.
///
/// A downstream crate passes its own crate dir, so the module it gets back is
/// the engine plus its rule pack.
pub fn wasm_pack_build(
    crate_dir: &Path,
    out_dir: &Path,
    extra_cargo_args: &[&str],
) -> Result<(String, Vec<u8>), String> {
    let skip = std::env::var_os("IMPECCABLE_BUNDLE_SKIP_WASM_PACK").is_some()
        || std::env::var_os("IMPECCABLE_XTASK_SKIP_WASM_PACK").is_some();
    if !skip {
        let wasm_pack = std::env::var("WASM_PACK").unwrap_or_else(|_| "wasm-pack".to_string());
        let mut cmd = Command::new(&wasm_pack);
        cmd.arg("build")
            .arg(crate_dir)
            .arg("--target")
            .arg("no-modules")
            .arg("--release")
            .arg("--no-typescript")
            .arg("--no-pack")
            .arg("--out-dir")
            .arg(out_dir)
            .arg("--out-name")
            .arg("impeccable")
            // Size profile for the module; native builds keep opt-level 3.
            .env("CARGO_PROFILE_RELEASE_OPT_LEVEL", "z")
            // wasm-pack refuses to build a `cdylib` whose Cargo.toml lives in
            // a workspace with `[profile.*]` overrides only when it cannot
            // find the target dir; keep it explicit.
            .env("CARGO_TARGET_DIR", target_dir_for(crate_dir));
        if !extra_cargo_args.is_empty() {
            cmd.arg("--");
            for arg in extra_cargo_args {
                cmd.arg(arg);
            }
        }
        let status = cmd
            .status()
            .map_err(|e| format!("wasm-pack build: failed to spawn {wasm_pack}: {e}"))?;
        if !status.success() {
            return Err(format!("wasm-pack build failed ({status})"));
        }
    }
    let glue_path = out_dir.join("impeccable.js");
    let wasm_path = out_dir.join("impeccable_bg.wasm");
    let glue = std::fs::read_to_string(&glue_path)
        .map_err(|e| format!("{}: {e}", glue_path.display()))?;
    let wasm = std::fs::read(&wasm_path).map_err(|e| format!("{}: {e}", wasm_path.display()))?;
    Ok((glue, wasm))
}

/// `CARGO_TARGET_DIR` for a wasm-pack run: the caller's, else the target dir
/// of the workspace `crate_dir` sits in (nearest ancestor with a
/// `Cargo.lock`), else the crate's own.
fn target_dir_for(crate_dir: &Path) -> PathBuf {
    if let Some(dir) = std::env::var_os("CARGO_TARGET_DIR") {
        return PathBuf::from(dir);
    }
    let abs = std::fs::canonicalize(crate_dir).unwrap_or_else(|_| crate_dir.to_path_buf());
    abs.ancestors()
        .find(|dir| dir.join("Cargo.lock").exists())
        .unwrap_or(&abs)
        .join("target")
}

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

    fn bundle_dir() -> PathBuf {
        Path::new(env!("CARGO_MANIFEST_DIR")).join("../../browser-bundle")
    }

    #[test]
    fn embedded_files_match_the_directory() {
        let mut on_disk: Vec<String> = std::fs::read_dir(bundle_dir())
            .expect("browser-bundle/")
            .map(|e| e.expect("dir entry").file_name().to_string_lossy().into_owned())
            .filter(|name| name.ends_with(".js"))
            .collect();
        on_disk.sort();
        let mut embedded: Vec<String> = PAGE_JS.iter().map(|(n, _)| n.to_string()).collect();
        embedded.sort();
        assert_eq!(
            embedded, on_disk,
            "browser-bundle/*.js changed: update PAGE_JS (and ORDER, if the file belongs in the page bundle)"
        );
    }

    #[test]
    fn embedded_sources_match_the_files_on_disk() {
        for (name, src) in PAGE_JS {
            let disk = std::fs::read_to_string(bundle_dir().join(name)).expect(name);
            assert_eq!(*src, disk, "{name} drifted from disk");
        }
    }

    #[test]
    fn in_page_bundle_has_the_expected_skeleton() {
        let out = in_page_bundle("const glue = 1;\n", &[0, 97, 115, 109]);
        assert!(out.starts_with(page_js("00-header.js").unwrap()));
        assert!(out.ends_with(page_js("99-footer.js").unwrap()));
        assert!(out.contains("// --- wasm-bindgen glue (generated by cargo xtask bundle) ---\nconst glue = 1;\n"));
        assert!(out.contains("const __IMPECCABLE_WASM_BYTES = 4;\n"));
        // base64 of the four-byte wasm preamble.
        assert!(out.contains("const __IMPECCABLE_WASM_B64 = \"AGFzbQ==\";\n"));
        assert!(out.contains("wasm_bindgen.initSync({ module: __impeccableWasmBytes() });"));
        // 60-offscreen.js is an extension-only piece.
        assert!(!out.contains(page_js("60-offscreen.js").unwrap()));
        // Order: probe and snapshot before the glue, scan after it.
        let glue_at = out.find("const glue = 1;").unwrap();
        assert!(out.find("__SNAP_STYLE_PROPS").unwrap() < glue_at);
        assert!(out.rfind("createImpeccableOverlay").unwrap() > glue_at);
    }

    #[test]
    fn extension_pieces_are_iifes_over_their_sources() {
        let ext = extension_pieces("const glue = 1;\n", &[0, 97, 115, 109], "[]\n");
        for (what, js) in [("snapshot", &ext.snapshot_js), ("overlay", &ext.overlay_js), ("core", &ext.core_js)] {
            assert!(js.starts_with("/**\n * Impeccable extension: "), "{what}");
            assert!(js.contains("(function () {\n"), "{what}");
            assert!(js.ends_with("})();\n"), "{what}");
        }
        assert!(ext.snapshot_js.contains("window.__impeccableSnapshot = __impeccableSnapshot;"));
        assert!(ext.overlay_js.contains("window.__impeccableCreateOverlay = createImpeccableOverlay;"));
        assert!(ext.core_js.contains("chrome.runtime.getURL('detector/core_bg.wasm')"));
        // The offscreen core fetches its module; nothing is base64 in there.
        assert!(!ext.core_js.contains("__IMPECCABLE_WASM_B64"));
        assert_eq!(ext.core_bg_wasm, vec![0, 97, 115, 109]);
        assert_eq!(ext.antipatterns_json, "[]\n");
    }

    #[test]
    fn capture_contract_holds() {
        check_capture_contract().unwrap();
    }

    #[test]
    fn registry_json_is_two_space_rows() {
        let json = registry_json();
        assert!(json.ends_with("]\n"));
        assert!(json.contains("\n  {\n    \"id\": "));
        let rows: Vec<serde_json::Value> = serde_json::from_str(&json).expect("valid json");
        assert_eq!(rows.len(), impeccable_core::registry::all_antipatterns().count());
        for row in &rows {
            for key in ["id", "name", "category", "description"] {
                assert!(row.get(key).is_some(), "row missing {key}: {row}");
            }
        }
    }
}