From 01cf67ca3519ba415b686f3246fed136d61f4e0e Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Tue, 21 Nov 2023 20:57:16 -0500
Subject: [PATCH] Simplify control flow parsing logic

---
 src/cpu/parse/control.rs | 139 +++++++++++++++++----------------------
 1 file changed, 61 insertions(+), 78 deletions(-)

diff --git a/src/cpu/parse/control.rs b/src/cpu/parse/control.rs
index e731ef5..042130e 100644
--- a/src/cpu/parse/control.rs
+++ b/src/cpu/parse/control.rs
@@ -1,93 +1,76 @@
 use crate::{
     cpu::{
         instructions::{control::ControlFlowInstruction, Instruction},
-        parse, register,
+        parse,
     },
     memory::{GetViewTuple, View},
+    register::Flag,
 };
 
-use super::{OpcodeParser, ParseOutput, ParseResult};
+use super::{OpcodeParser, OrParse, ParseOutput, ParseResult};
 
 pub struct Parser;
 
+enum ConditionalControlFlowType {
+    Call,
+    Jump,
+}
+
 impl OpcodeParser for Parser {
     fn parse_opcode(data: &View) -> ParseResult {
-        let opcode = parse::get_opcode_from_data(data);
-        match opcode {
-            0xC3 => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::JumpToImmediate { addr },
-            )),
-            0xCD => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::Call { addr },
-            )),
-            0xC2 => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::JumpToImmediateIfFlagMatches {
-                    flag: register::Flag::Zero,
-                    value: 0,
-                    addr,
-                },
-            )),
-            0xD2 => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::JumpToImmediateIfFlagMatches {
-                    flag: register::Flag::Carry,
-                    value: 0,
-                    addr,
-                },
-            )),
-            0xCA => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::JumpToImmediateIfFlagMatches {
-                    flag: register::Flag::Zero,
-                    value: 1,
-                    addr,
-                },
-            )),
-            0xDA => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::JumpToImmediateIfFlagMatches {
-                    flag: register::Flag::Carry,
-                    value: 1,
-                    addr,
-                },
-            )),
-            0xC4 => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::CallIfFlagMatches {
-                    flag: register::Flag::Zero,
-                    value: 0,
-                    addr,
-                },
-            )),
-            0xD4 => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::CallIfFlagMatches {
-                    flag: register::Flag::Carry,
-                    value: 0,
-                    addr,
-                },
-            )),
-            0xCC => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::CallIfFlagMatches {
-                    flag: register::Flag::Zero,
-                    value: 1,
-                    addr,
-                },
-            )),
-            0xDC => Ok(build_immediate_parameterized_control_flow_data(
-                data,
-                |addr| ControlFlowInstruction::CallIfFlagMatches {
-                    flag: register::Flag::Carry,
-                    value: 1,
-                    addr,
-                },
-            )),
-            _ => Err(parse::Error::UnknownOpcode(opcode)),
-        }
+        parse_unconditional_control_operation(data)
+            .or_parse(|_opcode| parse_conditional_control_operation(data))
+    }
+}
+
+fn parse_unconditional_control_operation(data: &View) -> ParseResult {
+    let opcode = parse::get_opcode_from_data(data);
+
+    match opcode {
+        0xC3 => Ok(build_immediate_parameterized_control_flow_data(
+            data,
+            |addr| ControlFlowInstruction::JumpToImmediate { addr },
+        )),
+        0xCD => Ok(build_immediate_parameterized_control_flow_data(
+            data,
+            |addr| ControlFlowInstruction::Call { addr },
+        )),
+        _ => Err(parse::Error::UnknownOpcode(opcode)),
+    }
+}
+
+fn parse_conditional_control_operation(data: &View) -> ParseResult {
+    let opcode = parse::get_opcode_from_data(data);
+
+    let (flag, value) = conditional_control_flow_flag_for_opcode(opcode)?;
+    let control_flow_type = conditional_control_flow_type_for_opcode(opcode)?;
+    match control_flow_type {
+        ConditionalControlFlowType::Jump => Ok(build_immediate_parameterized_control_flow_data(
+            data,
+            |addr| ControlFlowInstruction::JumpToImmediateIfFlagMatches { flag, value, addr },
+        )),
+        ConditionalControlFlowType::Call => Ok(build_immediate_parameterized_control_flow_data(
+            data,
+            |addr| ControlFlowInstruction::CallIfFlagMatches { flag, value, addr },
+        )),
+    }
+}
+
+fn conditional_control_flow_type_for_opcode(opcode: u8) -> Result<ConditionalControlFlowType, parse::Error> {
+    match opcode {
+        0xC2 | 0xD2 | 0xCA | 0xDA => Ok(ConditionalControlFlowType::Jump),
+        0xC4 | 0xD4 | 0xCC | 0xDC => Ok(ConditionalControlFlowType::Call),
+        _ => Err(parse::Error::UnknownOpcode(opcode)),
+    }
+}
+
+fn conditional_control_flow_flag_for_opcode(opcode: u8) -> Result<(Flag, u8), parse::Error> {
+    match opcode {
+        0xC2 | 0xC4 => Ok((Flag::Zero, 0)),
+        0xD2 | 0xD4 => Ok((Flag::Carry, 0)),
+        0xCA | 0xCC => Ok((Flag::Zero, 1)),
+        0xDA | 0xDC => Ok((Flag::Carry, 1)),
+        _ => Err(parse::Error::UnknownOpcode(opcode)),
     }
 }