// This is the userland implementation of translate-c which will be used by both stage1
// and stage2. Currently the only way it is used is with `zig translate-c-2`.

const std = @import("std");
const ast = std.zig.ast;
const Token = std.zig.Token;
use @import("clang.zig");

pub const Mode = enum {
    import,
    translate,
};

// TODO merge with Type.Fn.CallingConvention
pub const CallingConvention = enum {
    auto,
    c,
    cold,
    naked,
    stdcall,
};

pub const ClangErrMsg = Stage2ErrorMsg;

pub const Error = error{
    OutOfMemory,
    UnsupportedType,
};

const Context = struct {
    tree: *ast.Tree,
    source_buffer: *std.Buffer,
    err: Error,
    source_manager: *ZigClangSourceManager,

    fn a(c: *Context) *std.mem.Allocator {
        return &c.tree.arena_allocator.allocator;
    }

    /// Convert a null-terminated C string to a slice allocated in the arena
    fn str(c: *Context, s: [*]const u8) ![]u8 {
        return std.mem.dupe(c.a(), u8, std.mem.toSliceConst(u8, s));
    }

    /// Convert a clang source location to a file:line:column string
    fn locStr(c: *Context, loc: ZigClangSourceLocation) ![]u8 {
        const spelling_loc = ZigClangSourceManager_getSpellingLoc(c.source_manager, loc);
        const filename_c = ZigClangSourceManager_getFilename(c.source_manager, spelling_loc);
        const filename = if (filename_c) |s| try c.str(s) else ([]const u8)("(no file)");

        const line = ZigClangSourceManager_getSpellingLineNumber(c.source_manager, spelling_loc);
        const column = ZigClangSourceManager_getSpellingColumnNumber(c.source_manager, spelling_loc);
        return std.fmt.allocPrint(c.a(), "{}:{}:{}", filename, line, column);
    }
};

pub fn translate(
    backing_allocator: *std.mem.Allocator,
    args_begin: [*]?[*]const u8,
    args_end: [*]?[*]const u8,
    mode: Mode,
    errors: *[]ClangErrMsg,
    resources_path: [*]const u8,
) !*ast.Tree {
    const ast_unit = ZigClangLoadFromCommandLine(
        args_begin,
        args_end,
        &errors.ptr,
        &errors.len,
        resources_path,
    ) orelse {
        if (errors.len == 0) return error.OutOfMemory;
        return error.SemanticAnalyzeFail;
    };
    defer ZigClangASTUnit_delete(ast_unit);

    var tree_arena = std.heap.ArenaAllocator.init(backing_allocator);
    errdefer tree_arena.deinit();
    const arena = &tree_arena.allocator;

    const root_node = try arena.create(ast.Node.Root);
    root_node.* = ast.Node.Root{
        .base = ast.Node{ .id = ast.Node.Id.Root },
        .decls = ast.Node.Root.DeclList.init(arena),
        .doc_comments = null,
        // initialized with the eof token at the end
        .eof_token = undefined,
    };

    const tree = try arena.create(ast.Tree);
    tree.* = ast.Tree{
        .source = undefined, // need to use Buffer.toOwnedSlice later
        .root_node = root_node,
        .arena_allocator = undefined,
        .tokens = ast.Tree.TokenList.init(arena),
        .errors = ast.Tree.ErrorList.init(arena),
    };
    tree.arena_allocator = tree_arena;

    var source_buffer = try std.Buffer.initSize(&tree.arena_allocator.allocator, 0);

    var context = Context{
        .tree = tree,
        .source_buffer = &source_buffer,
        .source_manager = ZigClangASTUnit_getSourceManager(ast_unit),
        .err = undefined,
    };

    if (!ZigClangASTUnit_visitLocalTopLevelDecls(ast_unit, &context, declVisitorC)) {
        return context.err;
    }

    _ = try appendToken(&context, .Eof, "");
    tree.source = source_buffer.toOwnedSlice();
    return tree;
}

extern fn declVisitorC(context: ?*c_void, decl: *const ZigClangDecl) bool {
    const c = @ptrCast(*Context, @alignCast(@alignOf(Context), context));
    declVisitor(c, decl) catch |err| {
        c.err = err;
        return false;
    };
    return true;
}

fn declVisitor(c: *Context, decl: *const ZigClangDecl) Error!void {
    switch (ZigClangDecl_getKind(decl)) {
        .Function => {
            return visitFnDecl(c, @ptrCast(*const ZigClangFunctionDecl, decl));
        },
        .Typedef => {
            try emitWarning(c, ZigClangDecl_getLocation(decl), "TODO implement translate-c for typedefs");
        },
        .Enum => {
            try emitWarning(c, ZigClangDecl_getLocation(decl), "TODO implement translate-c for enums");
        },
        .Record => {
            try emitWarning(c, ZigClangDecl_getLocation(decl), "TODO implement translate-c for structs");
        },
        .Var => {
            try emitWarning(c, ZigClangDecl_getLocation(decl), "TODO implement translate-c for variables");
        },
        else => {
            const decl_name = try c.str(ZigClangDecl_getDeclKindName(decl));
            try emitWarning(c, ZigClangDecl_getLocation(decl), "ignoring {} declaration", decl_name);
        },
    }
}

fn visitFnDecl(c: *Context, fn_decl: *const ZigClangFunctionDecl) Error!void {
    const fn_name = try c.str(ZigClangDecl_getName_bytes_begin(@ptrCast(*const ZigClangDecl, fn_decl)));

    // TODO The C++ code has this:
    //if (get_global(c, fn_name)) {
    //    // we already saw this function
    //    return;
    //}

    const fn_decl_loc = ZigClangFunctionDecl_getLocation(fn_decl);
    const proto_node = transQualType(c, ZigClangFunctionDecl_getType(fn_decl), fn_decl_loc) catch |e| switch (e) {
        error.UnsupportedType => {
            try failDecl(c, fn_decl_loc, fn_name, "unable to resolve prototype of function");
            return;
        },
        else => return e,
    };
    const semi_tok = try appendToken(c, .Semicolon, ";");

    try emitWarning(c, fn_decl_loc, "TODO implement more translate-c for function decls");

    try c.tree.root_node.decls.push(proto_node);
}

fn transQualType(c: *Context, qt: ZigClangQualType, source_loc: ZigClangSourceLocation) !*ast.Node {
    return transType(c, ZigClangQualType_getTypePtr(qt), source_loc);
}

const RestorePoint = struct {
    context: *Context,
    token_index: ast.TokenIndex,
    src_buf_index: usize,

    fn activate(self: RestorePoint) void {
        self.context.tree.tokens.shrink(self.token_index);
        self.context.source_buffer.shrink(self.src_buf_index);
    }
};

fn makeRestorePoint(c: *Context) RestorePoint {
    return RestorePoint{
        .context = c,
        .token_index = c.tree.tokens.len,
        .src_buf_index = c.source_buffer.len(),
    };
}

fn transType(c: *Context, ty: *const ZigClangType, source_loc: ZigClangSourceLocation) !*ast.Node {
    const rp = makeRestorePoint(c);

    switch (ZigClangType_getTypeClass(ty)) {
        .Builtin => {
            const builtin_ty = @ptrCast(*const ZigClangBuiltinType, ty);
            switch (ZigClangBuiltinType_getKind(builtin_ty)) {
                else => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported builtin type"),
            }
        },
        .FunctionProto => {
            const fn_ty = @ptrCast(*const ZigClangFunctionType, ty);
            const cc = switch (ZigClangFunctionType_getCallConv(fn_ty)) {
                .C => CallingConvention.c,
                .X86StdCall => CallingConvention.stdcall,
                .X86FastCall => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 fastcall"),
                .X86ThisCall => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 thiscall"),
                .X86VectorCall => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 vectorcall"),
                .X86Pascal => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 pascal"),
                .Win64 => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: win64"),
                .X86_64SysV => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 64sysv"),
                .X86RegCall => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: x86 reg"),
                .AAPCS => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: aapcs"),
                .AAPCS_VFP => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: aapcs-vfp"),
                .IntelOclBicc => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: intel_ocl_bicc"),
                .SpirFunction => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: SPIR function"),
                .OpenCLKernel => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: OpenCLKernel"),
                .Swift => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: Swift"),
                .PreserveMost => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: PreserveMost"),
                .PreserveAll => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: PreserveAll"),
                .AArch64VectorCall => return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported calling convention: AArch64VectorCall"),
            };

            const fn_proto_ty = @ptrCast(*const ZigClangFunctionProtoType, ty);
            const is_var_args = ZigClangFunctionProtoType_isVariadic(fn_proto_ty);
            const param_count: usize = ZigClangFunctionProtoType_getNumParams(fn_proto_ty);
            var i: usize = 0;
            while (i < param_count) : (i += 1) {
                return revertAndWarn(rp, error.UnsupportedType, source_loc, "TODO: implement parameters for FunctionProto in transType");
            }
            // TODO check for always_inline attribute
            // TODO check for align attribute

            // extern fn (...) T
            const cc_tok = if (cc == .stdcall) try appendToken(c, .Keyword_stdcallcc, "stdcallcc") else null;
            const extern_tok = if (cc == .c) try appendToken(c, .Keyword_extern, "extern") else null;
            const fn_tok = try appendToken(c, .Keyword_fn, "fn");
            const lparen_tok = try appendToken(c, .LParen, "(");
            const var_args_tok = if (is_var_args) try appendToken(c, .Ellipsis3, "...") else null;
            const rparen_tok = try appendToken(c, .RParen, ")");

            const return_type_node = blk: {
                if (ZigClangFunctionType_getNoReturnAttr(fn_ty)) {
                    break :blk try appendIdentifier(c, "noreturn");
                } else {
                    return revertAndWarn(rp, error.UnsupportedType, source_loc, "TODO: non-noreturn FunctionProto return type");
                    //proto_node->data.fn_proto.return_type = trans_qual_type(c,
                    //        ZigClangFunctionType_getReturnType(fn_ty), source_loc);
                    //if (proto_node->data.fn_proto.return_type == nullptr) {
                    //    emit_warning(c, source_loc, "unsupported function proto return type");
                    //    return nullptr;
                    //}
                    //// convert c_void to actual void (only for return type)
                    //// we do want to look at the AstNode instead of ZigClangQualType, because
                    //// if they do something like:
                    ////     typedef Foo void;
                    ////     void foo(void) -> Foo;
                    //// we want to keep the return type AST node.
                    //if (is_c_void_type(proto_node->data.fn_proto.return_type)) {
                    //    proto_node->data.fn_proto.return_type = trans_create_node_symbol_str(c, "void");
                    //}
                }
            };

            const fn_proto = try c.a().create(ast.Node.FnProto);
            fn_proto.* = ast.Node.FnProto{
                .base = ast.Node{ .id = ast.Node.Id.FnProto },
                .doc_comments = null,
                .visib_token = null,
                .fn_token = fn_tok,
                .name_token = null,
                .params = ast.Node.FnProto.ParamList.init(c.a()),
                .return_type = ast.Node.FnProto.ReturnType{ .Explicit = return_type_node },
                .var_args_token = var_args_tok,
                .extern_export_inline_token = extern_tok,
                .cc_token = cc_tok,
                .async_attr = null,
                .body_node = null,
                .lib_name = null,
                .align_expr = null,
                .section_expr = null,
            };
            return &fn_proto.base;
        },

        else => {
            const type_name = c.str(ZigClangType_getTypeClassName(ty));
            return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported type: '{}'", type_name);
        },
    }
}

fn revertAndWarn(
    restore_point: RestorePoint,
    err: var,
    source_loc: ZigClangSourceLocation,
    comptime format: []const u8,
    args: ...,
) (@typeOf(err) || error{OutOfMemory}) {
    restore_point.activate();
    try emitWarning(restore_point.context, source_loc, format, args);
    return err;
}

fn emitWarning(c: *Context, loc: ZigClangSourceLocation, comptime format: []const u8, args: ...) !void {
    _ = try appendToken(c, .LineComment, "// {}: warning: " ++ format, c.locStr(loc), args);
}

fn failDecl(c: *Context, loc: ZigClangSourceLocation, name: []const u8, comptime format: []const u8, args: ...) !void {
    // const name = @compileError(msg);
    const const_tok = try appendToken(c, .Keyword_const, "const");
    const name_tok = try appendToken(c, .Identifier, "{}", name);
    const eq_tok = try appendToken(c, .Equal, "=");
    const builtin_tok = try appendToken(c, .Builtin, "@compileError");
    const lparen_tok = try appendToken(c, .LParen, "(");
    const msg_tok = try appendToken(c, .StringLiteral, "\"" ++ format ++ "\"", args);
    const rparen_tok = try appendToken(c, .RParen, ")");
    const semi_tok = try appendToken(c, .Semicolon, ";");

    const msg_node = try c.a().create(ast.Node.StringLiteral);
    msg_node.* = ast.Node.StringLiteral{
        .base = ast.Node{ .id = ast.Node.Id.StringLiteral },
        .token = msg_tok,
    };

    const call_node = try c.a().create(ast.Node.BuiltinCall);
    call_node.* = ast.Node.BuiltinCall{
        .base = ast.Node{ .id = ast.Node.Id.BuiltinCall },
        .builtin_token = builtin_tok,
        .params = ast.Node.BuiltinCall.ParamList.init(c.a()),
        .rparen_token = rparen_tok,
    };
    try call_node.params.push(&msg_node.base);

    const var_decl_node = try c.a().create(ast.Node.VarDecl);
    var_decl_node.* = ast.Node.VarDecl{
        .base = ast.Node{ .id = ast.Node.Id.VarDecl },
        .doc_comments = null,
        .visib_token = null,
        .thread_local_token = null,
        .name_token = name_tok,
        .eq_token = eq_tok,
        .mut_token = const_tok,
        .comptime_token = null,
        .extern_export_token = null,
        .lib_name = null,
        .type_node = null,
        .align_node = null,
        .section_node = null,
        .init_node = &call_node.base,
        .semicolon_token = semi_tok,
    };
    try c.tree.root_node.decls.push(&var_decl_node.base);
}

fn appendToken(c: *Context, token_id: Token.Id, comptime format: []const u8, args: ...) !ast.TokenIndex {
    const S = struct {
        fn callback(context: *Context, bytes: []const u8) Error!void {
            return context.source_buffer.append(bytes);
        }
    };
    const start_index = c.source_buffer.len();
    errdefer c.source_buffer.shrink(start_index);

    try std.fmt.format(c, Error, S.callback, format, args);
    const end_index = c.source_buffer.len();
    const token_index = c.tree.tokens.len;
    const new_token = try c.tree.tokens.addOne();
    errdefer c.tree.tokens.shrink(token_index);

    new_token.* = Token{
        .id = token_id,
        .start = start_index,
        .end = end_index,
    };
    try c.source_buffer.appendByte('\n');

    return token_index;
}

fn appendIdentifier(c: *Context, name: []const u8) !*ast.Node {
    const token_index = try appendToken(c, .Identifier, "{}", name);
    const identifier = try c.a().create(ast.Node.Identifier);
    identifier.* = ast.Node.Identifier{
        .base = ast.Node{ .id = ast.Node.Id.Identifier },
        .token = token_index,
    };
    return &identifier.base;
}

pub fn freeErrors(errors: []ClangErrMsg) void {
    ZigClangErrorMsg_delete(errors.ptr, errors.len);
}