//! Build the real Zed guest with Gleam, then leave the component where the
//! custom wasm linker (`scripts/gleam-wasm-linker`) can install it as the
//! crate's `cdylib` output (what Zed copies to `extension.wasm`).

use std::env;
use std::fs;
use std::path::{Path, PathBuf};
use std::process::Command;

fn main() {
    println!("cargo:rerun-if-changed=src/zed_gleam.gleam");
    println!("cargo:rerun-if-changed=gleam.toml");
    println!("cargo:rerun-if-changed=manifest.toml");
    println!("cargo:rerun-if-changed=scripts/gleam-wasm-linker");
    println!("cargo:rerun-if-env-changed=GLEAM");

    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
    let gleam = find_gleam(&manifest_dir);
    eprintln!("zed_gleam build.rs: using gleam at {}", gleam.display());

    // Fixed path the linker wrapper reads (relative to package root).
    let out_wasm = manifest_dir.join("target/gleam-extension.wasm");
    if let Some(parent) = out_wasm.parent() {
        fs::create_dir_all(parent).expect("create target/");
    }

    let status = Command::new(&gleam)
        .current_dir(&manifest_dir)
        .args(["export", "zed-extension"])
        .status()
        .unwrap_or_else(|err| {
            panic!(
                "failed to spawn gleam at {}: {err}\n\
                 Set GLEAM to a wasm-capable gleam binary \
                 (https://tangled.org/nandi.uk/gleam , branch wasm).",
                gleam.display()
            )
        });

    if !status.success() {
        panic!(
            "`gleam export zed-extension` failed (status {status}).\n\
             You need a Gleam build with Zed Wasm support:\n\
               https://tangled.org/nandi.uk/gleam  (branch wasm)\n\
               cargo build -p gleam\n\
               export GLEAM=/path/to/gleam/target/debug/gleam\n\
             Current GLEAM candidate: {}",
            gleam.display()
        );
    }

    // CLI writes package-root extension.wasm; copy to the linker input path.
    let exported = manifest_dir.join("extension.wasm");
    if !exported.is_file() {
        panic!(
            "gleam export succeeded but {} was not created",
            exported.display()
        );
    }
    fs::copy(&exported, &out_wasm).unwrap_or_else(|err| {
        panic!(
            "copy {} → {}: {err}",
            exported.display(),
            out_wasm.display()
        );
    });

    eprintln!(
        "zed_gleam build.rs: Gleam component ready at {}",
        out_wasm.display()
    );
}

fn find_gleam(manifest_dir: &Path) -> PathBuf {
    if let Ok(path) = env::var("GLEAM") {
        let p = PathBuf::from(path);
        if p.is_file() {
            return p;
        }
        panic!("GLEAM={p:?} is not a file");
    }

    // Common local checkouts (zed-gleam-native and gleam as siblings under code/).
    let candidates = [
        manifest_dir.join("../gleam/target/debug/gleam"),
        manifest_dir.join("../gleam/target/release/gleam"),
        manifest_dir.join("../../gleam/target/debug/gleam"),
        manifest_dir.join("../../gleam/target/release/gleam"),
    ];
    for candidate in candidates {
        if candidate.is_file() {
            return candidate.canonicalize().unwrap_or(candidate);
        }
    }

    // PATH
    PathBuf::from("gleam")
}