//! Convert a Project Sylpheed disc into the open asset tree the Godot port reads.
//!
//! The one rule this binary exists to enforce: **Godot never sees a disc format.**
//! Everything proprietary is decoded here and written out as JSON, PNG, Ogg
//! Vorbis and Ogg Theora, so the runtime — and anyone modding it — reads formats
//! a person can open.
//!
//! The output tree is **derived**: regenerated wholesale, never hand-edited. The
//! only thing this program takes from `authored/` is the screen-name map, and
//! every name it applies is stamped `name_source: "authored"` in the file it
//! lands in, so the export stays auditable against the disc.
//!
//! See `docs/FORMAT.md` for the schema and `docs/MISSION.md` for scope.

mod check;
mod screen;

use anyhow::{Context, Result};
use clap::Parser;
use serde::Serialize;
use std::path::{Path, PathBuf};
use sylpheed_formats::{pak::PakArchive, ui_layout};

/// The revision of `sylpheed-formats` this exporter is pinned to, recorded in
/// every file it writes. Keep in step with `Cargo.toml` — it is what makes an
/// export auditable a month later.
const FORMATS_REV: &str = "8b6dbcf";
const EXPORTER: &str = concat!("sylpheed-export ", env!("CARGO_PKG_VERSION"));

#[derive(Parser)]
#[command(about, version)]
struct Args {
    #[command(subcommand)]
    cmd: Cmd,
}

#[derive(clap::Subcommand)]
enum Cmd {
    /// Convert the disc into `export/`. Rewrites the tree wholesale.
    Export {
        /// Extracted disc root (the directory holding `dat/` and `hidden/`).
        #[arg(long, env = "SYLPHEED_DISC")]
        disc: PathBuf,
        /// Output tree. Rewritten wholesale — never hand-edit it.
        #[arg(long, default_value = "export")]
        out: PathBuf,
        /// Authored decisions applied during export (currently the screen names).
        #[arg(long, default_value = "authored")]
        authored: PathBuf,
    },
    /// Validate an export tree against `docs/FORMAT.md`, with no disc in hand.
    ///
    /// Reads the tree the way the Godot project will: as a stranger, with no
    /// access to the disc, the decoders or this exporter's internals.
    Check {
        #[arg(long, default_value = "export")]
        out: PathBuf,
    },
}

#[derive(Serialize)]
struct ManifestScreen {
    name: String,
    file: String,
    sprites: usize,
    #[serde(skip_serializing_if = "Vec::is_empty")]
    missing_sprites: Vec<String>,
}

#[derive(Serialize)]
struct Manifest {
    format: &'static str,
    exporter: &'static str,
    /// Which decoders produced this export. Pinned by revision, not floated.
    formats_rev: &'static str,
    disc: String,
    screens: Vec<ManifestScreen>,
    warnings: Vec<String>,
}

/// The authored `build index → name` map, keyed by archive path.
type NameMap = std::collections::BTreeMap<String, std::collections::BTreeMap<String, NameEntry>>;

#[derive(serde::Deserialize)]
struct NameEntry {
    name: String,
    #[serde(default)]
    why: Option<String>,
}

fn load_names(authored: &Path) -> Result<NameMap> {
    let path = authored.join("screen_names.json");
    if !path.exists() {
        return Ok(NameMap::new());
    }
    #[derive(serde::Deserialize)]
    struct File {
        archives: NameMap,
    }
    let raw = std::fs::read_to_string(&path)
        .with_context(|| format!("read {}", path.display()))?;
    Ok(serde_json::from_str::<File>(&raw)
        .with_context(|| format!("parse {}", path.display()))?
        .archives)
}

/// Every RATC entry of a UI pak that parses as a screen build.
///
/// The filter is `is_build` — a bundle with a `.rat` layout child. The developer
/// splash declares its sprites directly and has none, so it is invisible here;
/// that is P3's problem and is recorded as a manifest warning rather than
/// silently widened.
fn screen_builds(ar: &PakArchive) -> Vec<(usize, Vec<u8>)> {
    let mut out = Vec::new();
    for (i, e) in ar.entries().iter().enumerate() {
        let Ok(bytes) = ar.read(e) else { continue };
        if ui_layout::is_build(&bytes) {
            out.push((i, bytes));
        }
    }
    out
}

fn main() -> Result<()> {
    match Args::parse().cmd {
        Cmd::Export {
            disc,
            out,
            authored,
        } => run_export(&disc, &out, &authored),
        Cmd::Check { out } => {
            let n = check::run(&out)?;
            println!("{} screen(s) in {} validate against sylpheed.screen/2", n, out.display());
            Ok(())
        }
    }
}

fn run_export(disc: &Path, out: &Path, authored_dir: &Path) -> Result<()> {
    let names = load_names(authored_dir)?;

    // Derived output is regenerated wholesale: clear it, so a screen that stops
    // being exported stops existing rather than lingering as a stale file that
    // still validates.
    if out.exists() {
        std::fs::remove_dir_all(&out).context("clear the output tree")?;
    }
    std::fs::create_dir_all(&out)?;

    let archive = "dat/GP_TITLE.pak";
    let pak = disc.join(archive);
    let ar = PakArchive::open(&pak).with_context(|| format!("open {}", pak.display()))?;
    let builds = screen_builds(&ar);
    println!("{archive}: {} screen build(s)", builds.len());

    let archive_names = names.get(archive);
    let mut screens = Vec::new();
    for (build_idx, (entry, bytes)) in builds.iter().enumerate() {
        let authored = archive_names.and_then(|m| m.get(&build_idx.to_string()));
        let (name, name_source, why) = match authored {
            Some(e) => (e.name.clone(), "authored", e.why.clone()),
            // Nobody has identified this build. Emit a stable synthetic id and
            // say in the file that the name is not a recovered one.
            None => (format!("build_{build_idx:02}"), "index", None),
        };
        let ex = screen::export_build(
            &out,
            archive,
            *entry,
            build_idx,
            bytes,
            &name,
            name_source,
            why,
            "title",
            EXPORTER,
            FORMATS_REV,
        )
        .with_context(|| format!("export build {build_idx} of {archive}"))?;
        println!(
            "  [{build_idx}] entry {entry:<3} -> {}  ({} sprites{})",
            ex.json_path,
            ex.sprites,
            if ex.missing.is_empty() {
                String::new()
            } else {
                format!(", {} missing", ex.missing.len())
            }
        );
        screens.push(ManifestScreen {
            name: ex.name,
            file: ex.json_path,
            sprites: ex.sprites,
            missing_sprites: ex.missing,
        });
    }

    let manifest = Manifest {
        format: "sylpheed.manifest/1",
        exporter: EXPORTER,
        formats_rev: FORMATS_REV,
        disc: disc.display().to_string(),
        screens,
        warnings: vec![
            "P0 scope: GP_TITLE screen builds only. No audio, no video, no other archive."
                .into(),
            "The developer-logo splash is not here: it declares its sprites directly and has \
             no .rat layout child, so `is_build` does not see it. P3."
                .into(),
        ],
    };
    std::fs::write(
        out.join("manifest.json"),
        format!("{}\n", serde_json::to_string_pretty(&manifest)?),
    )?;
    println!("wrote {}/manifest.json", out.display());
    Ok(())
}