import { IdentId, idKey, Key } from "../ctx.ts";

type Ident = Key<IdentId>;

export class Ribs {
    private tyRibs: Rib[] = [];
    private valRibs: Rib[] = [];

    private constructor() {}

    public static withRootMod(): Ribs {
        const ribs = new Ribs();
        ribs.pushRib({ tag: "mod", mod: { items: new Map() } });
        return ribs;
    }

    public pushRib(kind: RibKind) {
        this.tyRibs.push({ bindings: new Map(), kind });
        this.valRibs.push({ bindings: new Map(), kind });
    }

    public hasTy(ident: IdentId): boolean {
        return this.tyRibs.at(-1)!.bindings.has(idKey(ident));
    }

    public defTy(ident: IdentId, res: Res) {
        this.tyRibs.at(-1)!.bindings.set(idKey(ident), res);
    }

    public hasVal(ident: IdentId): boolean {
        return this.valRibs.at(-1)!.bindings.has(idKey(ident));
    }

    public defVal(ident: IdentId, res: Res) {
        this.valRibs.at(-1)!.bindings.set(idKey(ident), res);
    }

    public checkpoint(): number {
        return this.tyRibs.length;
    }

    public returnToCheckpoint(checkpoint: number) {
        this.tyRibs = this.tyRibs.slice(checkpoint, this.tyRibs.length);
        this.valRibs = this.valRibs.slice(checkpoint, this.valRibs.length);
    }

    public nearestMod(): Mod {
        return [
            this.tyRibs
                .toReversed()
                .find((r) => r.kind.tag === "mod")!,
        ]
            .map((r) => (r.kind.tag === "mod" && r.kind.mod) as Mod)[0];
    }
}

export type Mod = {
    parent?: Mod;
    items: Map<Ident, Res>;
};

export type Rib = {
    bindings: Map<Ident, Res>;
    kind: RibKind;
};

export type RibKind =
    | { tag: "normal" }
    | { tag: "fn" }
    | { tag: "item" }
    | { tag: "mod"; mod: Mod };

export type Res =
    | { tag: "def"; def: Def }
    | { tag: "local"; id: number };

export type Def = {
    type: DefType;
    id: number;
};

export type DefType =
    | "mod"
    | "enum"
    | "struct"
    | "variant"
    | "ty_alias"
    | "ty_param"
    | "fn"
    | "use"
    | "field";