const std = @import("std");
const ast = @import("ast.zig");
const llvm = @import("llvm.zig");

pub const Codegen = struct {
    allocator: *std.mem.Allocator,

    pub fn init(allocator: *std.mem.Allocator) Codegen {
        return Codegen{ .allocator = allocator };
    }

    fn genNode(
        self: *Codegen,
        mod: llvm.LLVMModuleRef,
        node: *const ast.Node,
    ) !void {
        switch (node.*) {
            .Root => @panic("Should not have gotten Root"),
            .FnDecl => |decl| {
                const name = decl.func_name.lexeme;
                const name_cstr = try std.cstr.addNullByte(self.allocator, name);
                errdefer self.allocator.free(name_cstr);

                //const ret_type = decl.return_type.lexeme;

                var param_types = llvm.LLVMTypeList.init(self.allocator);
                errdefer param_types.deinit();

                for (decl.params.toSlice()) |param| {
                    try param_types.append(llvm.LLVMInt32Type());
                }

                var ret_type = llvm.LLVMFunctionType(
                    llvm.LLVMInt32Type(),
                    param_types.toSlice().ptr,
                    @intCast(c_uint, param_types.len),
                    0,
                );

                var func = llvm.LLVMAddFunction(mod, name_cstr.ptr, ret_type);
                var entry = llvm.LLVMAppendBasicBlock(func, c"entry");

                var builder = llvm.LLVMCreateBuilder();
                llvm.LLVMPositionBuilderAtEnd(builder, entry);

                // TODO codegen decl.body
                var tmp = llvm.LLVMBuildAdd(
                    builder,
                    llvm.LLVMGetParam(func, 0),
                    llvm.LLVMGetParam(func, 1),
                    c"tmp",
                );

                _ = llvm.LLVMBuildRet(builder, tmp);
                std.debug.warn("cgen: fn decl done\n");
            },
            else => {
                std.debug.warn("got unhandled Node {}\n", node.*);
                unreachable;
            },
        }
    }

    pub fn gen(self: *Codegen, root: *ast.Node) !void {
        std.debug.warn("cgen: start gen\n");
        var mod = llvm.LLVMModuleCreateWithName(c"awoo");
        defer llvm.LLVMDisposeModule(mod);
        std.debug.warn("cgen: got mod\n");

        for (root.Root.toSlice()) |child| {
            std.debug.warn("cgen: gen child {}\n", child);
            try self.genNode(mod, &child);
        }

        std.debug.warn("cgen: done\n");

        var err: ?[*]u8 = null;
        _ = llvm.LLVMVerifyModule(
            mod,
            llvm.LLVMVerifierFailureAction.LLVMAbortProcessAction,
            &err,
        );
        llvm.LLVMDisposeMessage(err);
    }
};