//! Extern interface registry (env.*) for diagnostics and optional slotting
//!
//! 目的: ExternCallの未登録/未対応時に候補提示やSTRICT診断を改善する。

use once_cell::sync::Lazy;

#[derive(Clone, Copy, Debug)]
pub struct ExternSpec {
    pub iface: &'static str,
    pub method: &'static str,
    pub min_arity: u8,
    pub max_arity: u8,
    pub slot: Option<u16>,
}

static EXTERNS: Lazy<Vec<ExternSpec>> = Lazy::new(|| {
    vec![
        // console
        ExternSpec {
            iface: "env.console",
            method: "log",
            min_arity: 1,
            max_arity: 255,
            slot: Some(10),
        },
        ExternSpec {
            iface: "env.console",
            method: "warn",
            min_arity: 1,
            max_arity: 255,
            slot: Some(10),
        },
        ExternSpec {
            iface: "env.console",
            method: "error",
            min_arity: 1,
            max_arity: 255,
            slot: Some(10),
        },
        ExternSpec {
            iface: "env.console",
            method: "info",
            min_arity: 1,
            max_arity: 255,
            slot: Some(10),
        },
        ExternSpec {
            iface: "env.console",
            method: "debug",
            min_arity: 1,
            max_arity: 255,
            slot: Some(10),
        },
        // debug
        ExternSpec {
            iface: "env.debug",
            method: "trace",
            min_arity: 1,
            max_arity: 255,
            slot: Some(11),
        },
        // runtime
        ExternSpec {
            iface: "env.runtime",
            method: "checkpoint",
            min_arity: 0,
            max_arity: 0,
            slot: Some(12),
        },
        // task
        ExternSpec {
            iface: "env.task",
            method: "cancelCurrent",
            min_arity: 0,
            max_arity: 0,
            slot: Some(30),
        },
        ExternSpec {
            iface: "env.task",
            method: "currentToken",
            min_arity: 0,
            max_arity: 0,
            slot: Some(31),
        },
        ExternSpec {
            iface: "env.task",
            method: "yieldNow",
            min_arity: 0,
            max_arity: 0,
            slot: Some(32),
        },
        ExternSpec {
            iface: "env.task",
            method: "sleepMs",
            min_arity: 1,
            max_arity: 1,
            slot: Some(33),
        },
        // future (scaffold)
        ExternSpec {
            iface: "env.future",
            method: "new",
            min_arity: 1,
            max_arity: 1,
            slot: Some(20),
        },
        ExternSpec {
            iface: "env.future",
            method: "birth",
            min_arity: 1,
            max_arity: 1,
            slot: Some(20),
        },
        ExternSpec {
            iface: "env.future",
            method: "set",
            min_arity: 2,
            max_arity: 2,
            slot: Some(21),
        },
        ExternSpec {
            iface: "env.future",
            method: "await",
            min_arity: 1,
            max_arity: 1,
            slot: Some(22),
        },
        // core-13 pure support shims
        ExternSpec {
            iface: "env.local",
            method: "get",
            min_arity: 1,
            max_arity: 1,
            slot: Some(40),
        },
        ExternSpec {
            iface: "env.local",
            method: "set",
            min_arity: 2,
            max_arity: 2,
            slot: Some(41),
        },
        ExternSpec {
            iface: "env.box",
            method: "new",
            min_arity: 1,
            max_arity: 255,
            slot: Some(50),
        },
        ExternSpec {
            iface: "env.box_introspect",
            method: "kind",
            min_arity: 1,
            max_arity: 1,
            slot: Some(51),
        },
        // basic env access
        ExternSpec {
            iface: "env",
            method: "get",
            min_arity: 1,
            max_arity: 1,
            slot: Some(60),
        },
        // host providers (delegate path)
        ExternSpec {
            iface: "env.mirbuilder",
            method: "emit",
            min_arity: 1,
            max_arity: 1,
            slot: Some(70),
        },
        ExternSpec {
            iface: "env.codegen",
            method: "emit_object",
            min_arity: 1,
            max_arity: 2,
            slot: Some(71),
        },
        // hostbridge trampoline (dev/testing)
        ExternSpec {
            iface: "hostbridge",
            method: "extern_invoke",
            min_arity: 2,
            max_arity: 3,
            slot: Some(80),
        },
    ]
});

pub fn resolve(iface: &str, method: &str) -> Option<ExternSpec> {
    EXTERNS
        .iter()
        .copied()
        .find(|e| e.iface == iface && e.method == method)
}

pub fn known_for_iface(iface: &str) -> Vec<&'static str> {
    let mut v: Vec<&'static str> = EXTERNS
        .iter()
        .filter(|e| e.iface == iface)
        .map(|e| e.method)
        .collect();
    v.sort();
    v.dedup();
    v
}

pub fn all_ifaces() -> Vec<&'static str> {
    let mut v: Vec<&'static str> = EXTERNS.iter().map(|e| e.iface).collect();
    v.sort();
    v.dedup();
    v
}

/// Resolve slot id for an extern call (if assigned)
pub fn resolve_slot(iface: &str, method: &str) -> Option<u16> {
    resolve(iface, method).and_then(|s| s.slot)
}

/// Check arity against registry; returns Ok or an explanatory error string
pub fn check_arity(iface: &str, method: &str, argc: usize) -> Result<(), String> {
    if let Some(s) = resolve(iface, method) {
        if argc as u8 >= s.min_arity && argc as u8 <= s.max_arity {
            Ok(())
        } else {
            Err(format!(
                "arity {} out of range {}..{}",
                argc, s.min_arity, s.max_arity
            ))
        }
    } else {
        Err("unknown extern".to_string())
    }
}