default rel

%include "src/ast.inc"

extern panic
extern vec_extend
extern vec_get

global codegen_function

section .rdata
    SECTION_TEXT db "section .text", 10
    SECTION_TEXT_LEN equ $ - SECTION_TEXT
    GLOBAL_ db "global "
    GLOBAL_LEN equ $ - GLOBAL_
    COLON_NL db ":", 10
    COLON_NL_LEN equ $ - COLON_NL
    RET_NL db "ret", 10
    RET_NL_LEN equ $ - RET_NL

section .text
;; start-structs
;; struct CodegenCtx {
;;   ast: *const Ast,
;;   text: Vec<u8>,
;; }
;; end-structs

;; rdi: *Ctx
;; rsi: function index
;; define-fn: fn codegen_function(ast: *const CodegenCtx, func_idx: u64) -> ()
codegen_function:
    push rbp
    mov rbp, rsp
    push rbx

    ; register-bitset [72..88]  [a,b,c,d,di,si,sp,bp,8,9,10,11,12,13,14,15]
    ; stack-vars: Vec<(index, offset)> [32..72]
    ; current_stack_size: [24..32]
    ; func_idx [16..24]
    ; ast [8..16]
    ; ctx [0..8]
    sub rsp, 88
    mov [rsp], rdi              ; ctx
    mov rax, [rdi]
    mov [rsp + 8], rax          ; ast
    mov [rsp + 16], rsi         ; func_idx

    bts qword [rsp + 72], 7           ; mark rbp as used
    bts qword [rsp + 72], 6           ; mark rsp as used

    ; push "section .text\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    lea rsi, [rel SECTION_TEXT]
    mov rdx, SECTION_TEXT_LEN
    call vec_extend

    mov rdi, [rsp + 8]          ; ast
    mov rsi, [rsp + 16]         ; func_idx
    call vec_get
    cmp byte [rax + 0], AST_FUNCTION ; AstNode.kind
    mov rbx, [rax + 8]          ; AstNode.data
    jne .panic

    ; push "global {function_name}\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    lea rsi, [rel GLOBAL_]
    mov rdx, GLOBAL_LEN
    call vec_extend
    ; get function name
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    mov rsi, [rbx + 0]         ; AstFunction.name
    mov rdx, [rbx + 8]         ; AstFunction.name_len
    call vec_extend
    ; push "\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    lea rsi, [rel COLON_NL]
    inc rsi
    mov rdx, 1
    call vec_extend
    ; push "{function_name}:\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    mov rsi, [rbx + 0]         ; AstFunction.name
    mov rdx, [rbx + 8]         ; AstFunction.name_len
    call vec_extend
    ; push ":\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    lea rsi, [rel COLON_NL]
    mov rdx, 2
    call vec_extend
    

    ; TODO: generate function body

    ; push "ret\n"
    mov rdi, [rsp]              ; ctx
    lea rdi, [rdi + 8]          ; &ctx.text
    lea rsi, [rel RET_NL]
    mov rdx, RET_NL_LEN
    call vec_extend

    add rsp, 88
    pop rbx
    pop rbp
    ret

.panic:
    call panic