thi-ng/umbrella

import { topoSort } from "@thi.ng/arrays/topo-sort";
import { isString } from "@thi.ng/checks/is-string";
import { unsupported } from "@thi.ng/errors/unsupported";
import { capitalize } from "@thi.ng/strings/case";
import type {
    CodeGenOpts,
    CodeGenOptsBase,
    Field,
    FuncPointer,
    ICodeGen,
    Struct,
    TypeColl,
    Union,
    WasmPrim,
} from "./api.js";
import { classifyField } from "./internal/classify.js";
import {
    ensureStringArray,
    enumName,
    isOpaque,
    isPadding,
    isStringSlice,
    isStruct,
    isUnion,
    isWasmString,
    prefixLines,
    sliceTypes,
    withIndentation,
} from "./internal/utils.js";

const PRIM_ALIASES = {
    i8: "int8_t",
    u8: "uint8_t",
    i16: "int16_t",
    u16: "uint16_t",
    i32: "int32_t",
    u32: "uint32_t",
    i64: "int64_t",
    u64: "uint64_t",
    f32: "float",
    f64: "double",
};

/**
 * Zig code generator options.
 */
export interface C11Opts extends CodeGenOptsBase {
    /**
     * Optional name prefix for generated types, e.g. `WASM_`.
     */
    typePrefix: string;
}

/**
 * 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 C11 = (opts: Partial<C11Opts> = {}) => {
    const { typePrefix = "" } = opts;
    const INDENT = "    ";
    const SCOPES: [RegExp, RegExp] = [/\{$/, /^\}[ A-Za-z0-9_]*[;,]?$/];

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

        pre: (coll, opts) => {
            const res = [
                "#pragma once",
                "",
                "#ifdef __cplusplus",
                `extern "C" {`,
                "#endif",
                opts.debug ? "\n#include <stdalign.h>" : "",
                `#include "wasmapi.h"`,
                "",
            ];
            // pre-declare any primitive slice types used (e.g. `U8Slice`)
            const slices = sliceTypes(coll);
            for (let id of slices) {
                const prim = PRIM_ALIASES[<WasmPrim>id];
                if (!prim) continue;
                res.push(__sliceDef(prim, typePrefix, capitalize(id!)));
            }
            // ...then pre-declare any custom types in dependency order
            for (let id of __declOrder(coll)) {
                const type = coll[id];
                if (type.type == "funcptr") {
                    res.push(
                        __funcptr(<FuncPointer>type, coll, opts, typePrefix)
                    );
                } else {
                    res.push(
                        `\ntypedef ${type.type} ${typePrefix}${type.name} ${typePrefix}${type.name};`
                    );
                }
                if (slices.has(id)) {
                    const [ptr, name] =
                        id === "opaque"
                            ? ["void*", "Opaque"]
                            : [typePrefix + id, capitalize(id!)];
                    res.push(__sliceDef(ptr, typePrefix, name));
                }
            }
            if (opts.pre) res.push("", ...ensureStringArray(opts.pre));
            return res.join("\n");
        },

        post: () => {
            const res = [];
            if (opts.post) res.push(...ensureStringArray(opts.post), "");
            res.push("#ifdef __cplusplus", "}", "#endif", "");
            return res.join("\n");
        },

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

        enum: (e, _, acc, opts) => {
            if (!(e.tag === "i32" || e.tag === "u32")) {
                unsupported(
                    `enum ${e.name} must be a i32/u32 in C, but got '${e.tag}'`
                );
            }
            const name = typePrefix + e.name;
            const lines: string[] = [];
            lines.push(`enum ${name} {`);
            for (let v of e.values) {
                let line: string;
                if (!isString(v)) {
                    v.doc && gen.doc(v.doc, lines, opts);
                    line = enumName(opts, v.name);
                    if (v.value != null) line += ` = ${v.value}`;
                } else {
                    line = enumName(opts, v);
                }
                lines.push(line + ",");
            }
            lines.push(`};`, "");
            acc.push(...withIndentation(lines, INDENT, ...SCOPES));
        },

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

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

        // funcpointers are emitted in `pre` phase above
        funcptr: () => {},
    };
    return gen;
};

/**
 * Generates source code for given {@link Struct} or {@link Union}.
 *
 * @internal
 */
const __generateFields = (
    gen: ICodeGen,
    parent: Struct | Union,
    coll: TypeColl,
    opts: CodeGenOpts,
    typePrefix: string
) => {
    const res: string[] = [];
    const ftypes: Record<string, string> = {};
    const isUnion = parent.type === "union";
    const name = typePrefix + parent.name;
    let padID = 0;
    for (let f of parent.fields) {
        // autolabel explicit padding fields
        if (isPadding(f)) {
            res.push(`uint8_t __pad${padID++}[${f.pad}];`);
            continue;
        }
        f.doc && gen.doc(f.doc, res, opts);
        const { type, decl, sentinel } = __fieldType(f, coll, opts, typePrefix);
        ftypes[f.name] = type;
        res.push(decl + ";");
        if (sentinel) {
            res.push(
                `// Hidden sentinel. Must be manually initialized to ${
                    f.sentinel || 0
                }`,
                `${sentinel} __${f.name}Sentinel;`
            );
        }
    }
    res.push("};");

    if (opts.debug) {
        const fn = (fname: string, body: string) =>
            res.push(
                "",
                `size_t __attribute__((used)) ${name}_${fname}() {`,
                `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(${ftypes[f.name]})`);
            !isUnion && fn(f.name + "_offset", `offsetof(${name}, ${f.name})`);
            fn(f.name + "_size", `sizeof(${ftypes[f.name]})`);
        }
    }
    res.push("");
    return res;
};

/**
 * Returns the C type name and declaration (incl. field name) for a given
 * {@link Field}.
 *
 * @internal
 */
const __fieldType = (
    f: Field,
    coll: TypeColl,
    opts: CodeGenOpts,
    prefix: string
) => {
    let type = f.type;
    let decl: string;
    let sentinel: string;
    const { classifier, isConst } = classifyField(f, coll);
    const $isConst = isConst ? "Const" : "";
    const __ptr = () => {
        decl = `${type}* ${f.name}`;
        type = `${type}*`;
    };
    const __array = () => {
        decl = `${type} ${f.name}[${f.len}]`;
        type = `${type}[${f.len}]`;
    };
    const __slice = () => {
        type += "Slice";
        decl = `${type} ${f.name}`;
    };
    if (isWasmString(f.type)) {
        const useStrSlice = isStringSlice(opts.stringType);
        type =
            prefix +
            (useStrSlice ? `${$isConst}String` : `${$isConst}StringPtr`);
        switch (classifier) {
            case "strPtr":
            case "strPtrFixed":
            case "strPtrMulti":
                __ptr();
                break;
            case "strSlice":
                __slice();
                break;
            case "strArray":
                __array();
                break;
            default:
                decl = `${type} ${f.name}`;
        }
    } else if (isOpaque(f.type)) {
        type = `${prefix}${$isConst}OpaquePtr`;
        switch (classifier) {
            case "opaquePtr":
            case "opaquePtrFixed":
            case "opaquePtrMulti":
                __ptr();
                break;
            case "opaqueSlice":
                __slice();
                break;
            case "opaqueArray":
                __array();
                break;
            default:
                decl = `${type} ${f.name}`;
        }
    } else {
        const $const = isConst ? "const " : "";
        type = PRIM_ALIASES[<WasmPrim>type] || prefix + type;
        switch (classifier) {
            case "ptr":
            case "ptrFixed":
            case "ptrMulti":
            case "enumPtr":
            case "enumPtrFixed":
            case "enumPtrMulti":
                type = `${$const}${type}*`;
                decl = `${type} ${f.name}`;
                break;
            case "slice":
            case "enumSlice":
                type = `${prefix}${$isConst}${capitalize(f.type)}Slice`;
                decl = `${type} ${f.name}`;
                break;
            case "array":
            case "enumArray":
                __array();
                if (f.sentinel != null) {
                    sentinel = PRIM_ALIASES[<WasmPrim>f.type];
                }
                break;
            case "vec":
                unsupported("C doesn't support vector");
            default:
                decl = `${type} ${f.name}`;
        }
    }
    return {
        type: type,
        decl: decl!,
        sentinel: sentinel!,
    };
};

/**
 * Takes a {@link TypeColl} and returns user type names in dependency order.
 *
 * @param coll
 *
 * @internal
 */
const __declOrder = (coll: TypeColl) =>
    topoSort(coll, (type) => {
        const fields =
            isStruct(type) || isUnion(type)
                ? type.fields
                : type.type === "funcptr"
                ? (<FuncPointer>type).args
                : undefined;
        return fields
            ? fields.map((x) => x.type).filter((x) => !!coll[x])
            : undefined;
    });

/**
 * Generates C `typedef` for given {@link FuncPointer} spec.
 *
 * @param ptr
 * @param coll
 * @param opts
 * @param typePrefix
 *
 * @internal
 */
const __funcptr = (
    ptr: FuncPointer,
    coll: TypeColl,
    opts: CodeGenOpts,
    typePrefix: string
) => {
    const name = typePrefix + ptr.name;
    const args = ptr.args
        .map((a) => __fieldType(a, coll, opts, typePrefix).decl)
        .join(", ");
    const rtype =
        ptr.rtype === "void"
            ? ptr.rtype
            : __fieldType(
                    { name: "return", ...ptr.rtype },
                    coll,
                    opts,
                    typePrefix
              ).type;
    return `typedef ${rtype} (*${name})(${args});`;
};

/**
 * Generates `typedef`s for a slice emulation struct of given pointer type.
 *
 * @param ptr
 * @param prefix
 * @param name
 *
 *  @internal
 */
const __sliceDef = (ptr: string, prefix: string, name: string) =>
    `\ntypedef struct { ${ptr}* ptr; size_t len; } ${prefix}${name}Slice;` +
    `\ntypedef struct { const ${ptr}* ptr; size_t len; } ${prefix}Const${name}Slice;`;