thi-ng/umbrella

import { isNumber } from "@thi.ng/checks";
import { isString } from "@thi.ng/checks/is-string";
import { illegalArgs } from "@thi.ng/errors/illegal-arguments";
import { capitalize } from "@thi.ng/strings/case";
import type {
    CodeGenOpts,
    CodeGenOptsBase,
    Field,
    FuncPointer,
    ICodeGen,
    Struct,
    TypeColl,
    Union,
} from "./api.js";
import { classifyField } from "./internal/classify.js";
import {
    defaultValue,
    ensureLines,
    ensureStringArray,
    isOpaque,
    isPadding,
    isStringSlice,
    isUnion,
    isWasmString,
    prefixLines,
    sliceTypes,
    withIndentation,
} from "./internal/utils.js";

/**
 * Zig code generator options.
 */
export interface ZigOpts extends CodeGenOptsBase {}

/**
 * Zig code generator. Call with options and then pass to {@link generateTypes}
 * (see its docs for further usage).
 *
 * @remarks
 * This codegen generates struct and enum definitions for a {@link TypeColl}
 * given to {@link generateTypes}.
 *
 * @param opts
 */
export const ZIG = (opts: Partial<ZigOpts> = {}) => {
    const INDENT = "    ";
    const SCOPES: [RegExp, RegExp] = [/\{$/, /(?<!\{.*)\}\)?[;,]?$/];

    const gen: ICodeGen = {
        id: "zig",

        pre: (coll) => {
            const res = [
                `const std = @import("std");`,
                `const bindgen = @import("wasm-api-bindgen");`,
            ];
            for (let type of sliceTypes(coll)) {
                if (type !== "string" && type !== "opaque") {
                    const name = capitalize(type!);
                    res.push(
                        `\npub const ${name}Slice = bindgen.Slice([]${type}, [*]${type});`,
                        `pub const Const${name}Slice = bindgen.Slice([]const ${type}, [*]const ${type});`
                    );
                }
            }
            if (opts.pre) res.push("", ...ensureStringArray(opts.pre));
            return res.join("\n");
        },

        post: () =>
            opts.post
                ? isString(opts.post)
                    ? opts.post
                    : opts.post.join("\n")
                : "",

        doc: (doc, acc, opts, topLevel = false) => {
            acc.push(
                ...prefixLines(topLevel ? "//! " : "/// ", doc, opts.lineWidth)
            );
        },

        enum: (e, _, acc, opts) => {
            const lines: string[] = [];
            lines.push(`pub const ${e.name} = enum(${e.tag}) {`);
            for (let v of e.values) {
                let line: string;
                if (!isString(v)) {
                    v.doc && gen.doc(v.doc, lines, opts);
                    line = v.name;
                    if (v.value != null) line += ` = ${v.value}`;
                } else {
                    line = v;
                }
                lines.push(line + ",");
            }
            if (e.body?.zig) {
                lines.push("", ...ensureLines(e.body!.zig, "impl"), "");
            }
            lines.push("};", "");
            acc.push(...withIndentation(lines, INDENT, ...SCOPES));
        },

        struct: (struct, coll, acc, opts) => {
            acc.push(
                ...withIndentation(
                    [
                        `pub const ${struct.name} = extern struct {`,
                        ...__generateFields(gen, struct, coll, opts),
                    ],
                    INDENT,
                    ...SCOPES
                )
            );
        },

        union: (union, coll, acc, opts) => {
            acc.push(
                ...withIndentation(
                    [
                        `pub const ${union.name} = extern union {`,
                        ...__generateFields(gen, union, coll, opts),
                    ],
                    INDENT,
                    ...SCOPES
                )
            );
        },

        funcptr: (ptr, coll, acc, opts) => {
            const args = ptr.args
                .map((a) => `${a.name}: ${fieldType(a, ptr, coll, opts).type}`)
                .join(", ");
            const rtype =
                ptr.rtype === "void"
                    ? ptr.rtype
                    : fieldType(
                            { name: "return", ...ptr.rtype },
                            ptr,
                            coll,
                            opts
                      ).type;
            acc.push(
                `pub const ${ptr.name} = *const fn (${args}) callconv(.C) ${rtype};`,
                ""
            );
        },
    };
    return gen;
};

const __generateFields = (
    gen: ICodeGen,
    parent: Struct | Union,
    coll: TypeColl,
    opts: CodeGenOpts
) => {
    const res: string[] = [];
    const ftypes: Record<string, string> = {};
    const name = parent.name;
    let padID = 0;
    for (let f of parent.fields) {
        // autolabel explicit padding fields
        if (isPadding(f)) {
            res.push(`__pad${padID}: [${f.pad}]u8,`);
            padID++;
            continue;
        }
        f.doc && gen.doc(f.doc, res, opts);
        const { type, defaultVal } = fieldType(f, parent, coll, opts);
        ftypes[f.name] = type;
        res.push(`${f.name}: ${type}${defaultVal},`);
    }
    if (parent.body?.zig) {
        res.push("", ...ensureLines(parent.body!.zig, "impl"), "");
    }
    res.push("};");

    if (opts.debug) {
        const fn = (fname: string, body: string) =>
            res.push(
                "",
                `export fn ${name}_${fname}() usize {`,
                `return ${body};`,
                `}`
            );

        fn("align", `@alignOf(${name})`);
        fn("size", `@sizeOf(${name})`);

        for (let f of parent.fields) {
            if (isPadding(f)) continue;
            fn(f.name + "_align", `@alignOf(${ftypes[f.name]})`);
            !isUnion(parent) &&
                fn(f.name + "_offset", `@offsetOf(${name}, "${f.name}")`);
            fn(f.name + "_size", `@sizeOf(${ftypes[f.name]})`);
        }
    }
    res.push("");
    return res;
};

/** @internal */
export const fieldType = (
    f: Field,
    parent: Struct | Union | FuncPointer,
    coll: TypeColl,
    opts: CodeGenOpts
) => {
    let type = f.type;
    let defaultVal = defaultValue(f, "zig");
    const { classifier, isConst } = classifyField(f, coll);
    const $isConst = isConst ? "Const" : "";
    if (isWasmString(f.type)) {
        type = isStringSlice(opts.stringType)
            ? `bindgen.${$isConst}String`
            : `bindgen.${$isConst}StringPtr`;
        switch (classifier) {
            case "strPtr":
                type = `*${type}`;
                break;
            case "strPtrFixed":
                type = `*[${f.len}]${type}`;
                break;
            case "strPtrMulti":
                type = `[*]${type}`;
                break;
            case "strSlice":
                type += "Slice";
                break;
            case "strArray":
                type = `[${f.len}]${type}`;
                break;
        }
    } else if (isOpaque(f.type)) {
        type = `bindgen.${$isConst}OpaquePtr`;
        switch (classifier) {
            case "opaquePtr":
                type = `*${type}`;
                break;
            case "opaquePtrFixed":
                type = `*[${f.len}]${type}`;
                break;
            case "opaquePtrMulti":
                type = `[*]${type}`;
                break;
            case "opaqueSlice":
                type += "Slice";
                break;
            case "opaqueArray":
                type = `[${f.len}]${type}`;
                break;
        }
    } else {
        const $const = isConst ? "const " : "";
        const sentinel = f.sentinel != null ? `:${f.sentinel}` : "";
        switch (classifier) {
            case "ptr":
            case "enumPtr":
                type = `*${$const}${type}`;
                break;
            case "ptrFixed":
            case "enumPtrFixed":
                type = `*${$const}[${f.len}${sentinel}]${type}`;
                break;
            case "ptrMulti":
            case "enumPtrMulti":
                type = `[*${sentinel}]${$const}${type}`;
                break;
            case "slice":
            case "enumSlice":
                type = `${$isConst}${capitalize(f.type)}Slice`;
                break;
            case "array":
            case "enumArray":
                type = `[${f.len}${sentinel}]${type}`;
                break;
            case "vec":
                type = `@Vector(${f.len}, ${type})`;
                break;
        }
    }
    if (f.optional) type = "?" + type;
    if (defaultVal != undefined) {
        if (!(isString(defaultVal) || isNumber(defaultVal))) {
            illegalArgs(
                `wrong default value for ${parent.name}.${f.name} (${defaultVal})`
            );
        }
    }
    return {
        type,
        defaultVal: defaultVal != undefined ? ` = ${defaultVal}` : "",
    };
};