Started working on stepping execution for QuestRunner.

Step over and step in kind of work but there are still bugs. Step out is unimplemented.

src/core/util.ts

@@ -41,3 +41,21 @@ export function basename(filename: string): string {
 
     return filename;
 }
+
+export function defined<T>(value: T | undefined): asserts value is T {
+    if (value === undefined) {
+        throw new Error("Assertion Error: value is undefined.");
+    }
+}
+
+export function assert(condition: any, msg?: string): asserts condition {
+    if (!condition) {
+        let full_msg = "Assertion Error";
+        
+        if (msg) {
+            full_msg += ": " + msg;
+        }
+
+        throw new Error(full_msg);
+    }
+}

src/quest_editor/QuestRunner.ts

@@ -1,9 +1,15 @@
-import { ExecutionResult, VirtualMachine } from "./scripting/vm";
+import { ExecutionResult, VirtualMachine, ExecutionLocation } from "./scripting/vm";
 import { QuestModel } from "./model/QuestModel";
 import { VirtualMachineIO } from "./scripting/vm/io";
-import { AsmToken } from "./scripting/instructions";
+import { AsmToken, SegmentType, InstructionSegment, Segment, Instruction } from "./scripting/instructions";
 import { quest_editor_store } from "./stores/QuestEditorStore";
 import { asm_editor_store } from "./stores/AsmEditorStore";
+import { defined, assert } from "../core/util";
+import {
+    OP_CALL,
+    OP_VA_CALL,
+    OP_SWITCH_CALL,
+} from "./scripting/opcodes";
 
 const logger = quest_editor_store.get_logger("quest_editor/QuestRunner");
 
@@ -11,9 +17,19 @@ function srcloc_to_string(srcloc: AsmToken): string {
     return `[${srcloc.line_no}:${srcloc.col}]`;
 }
 
+function execloc_to_string(execloc: ExecutionLocation) {
+    return `[${execloc.seg_idx}:${execloc.inst_idx}]`;
+}
+
 export class QuestRunner {
     private readonly vm: VirtualMachine;
+    private quest?: QuestModel;
     private animation_frame?: number;
+    /**
+     * Invisible breakpoints that help with stepping over/in/out.
+     */
+    private readonly stepping_breakpoints: number[] = [];
+    private break_on_next = false;
 
     constructor() {
         this.vm = new VirtualMachine(this.create_vm_io());
@@ -24,12 +40,72 @@ export class QuestRunner {
             cancelAnimationFrame(this.animation_frame);
         }
 
+        this.quest = quest;
+
         this.vm.load_object_code(quest.object_code);
         this.vm.start_thread(0);
 
         this.schedule_frame();
     }
 
+    public resume(): void {
+        this.schedule_frame();
+    }
+
+    public step_over(): void {
+        const execloc = this.vm.get_current_execution_location();
+
+        defined(this.quest);
+
+        const src_segment = this.get_instruction_segment_by_index(execloc.seg_idx);
+        const cur_instr = src_segment.instructions[execloc.inst_idx];
+        const dst_label = this.get_step_innable_instruction_label_argument(cur_instr);
+
+        // nothing to step over, just break on next instruction
+        if (dst_label === undefined) {
+            this.break_on_next = true;
+        }
+        // set a breakpoint on the next line
+        else {
+            const next_execloc = new ExecutionLocation(execloc.seg_idx, execloc.inst_idx + 1);
+
+            // next line is in the next segment
+            if (next_execloc.inst_idx >= src_segment.instructions.length) {
+                next_execloc.seg_idx++;
+                next_execloc.inst_idx = 0;
+            }
+
+            const dst_segment = this.get_instruction_segment_by_index(next_execloc.seg_idx);
+            const dst_instr = dst_segment.instructions[next_execloc.inst_idx];
+            if (dst_instr.asm && dst_instr.asm.mnemonic) {
+                this.stepping_breakpoints.push(dst_instr.asm.mnemonic.line_no);
+            }
+        }
+    }
+
+    public step_in(): void {
+        const execloc = this.vm.get_current_execution_location();
+        const src_segment = this.get_instruction_segment_by_index(execloc.seg_idx);
+        const cur_instr = src_segment.instructions[execloc.inst_idx];
+        const dst_label = this.get_step_innable_instruction_label_argument(cur_instr);
+
+        // not a step-innable instruction, behave like step-over
+        if (dst_label === undefined) {
+            this.step_over();
+        }
+        // can step-in
+        else {
+            const dst_segment = this.get_instruction_segment_by_label(dst_label);
+            const dst_instr = dst_segment.instructions[0];
+            
+            if (dst_instr.asm && dst_instr.asm.mnemonic) {
+                this.stepping_breakpoints.push(dst_instr.asm.mnemonic.line_no);
+            }
+
+            this.schedule_frame();
+        }
+    }
+
     private schedule_frame(): void {
         this.animation_frame = requestAnimationFrame(this.execution_loop);
     }
@@ -37,16 +113,24 @@ export class QuestRunner {
     private execution_loop = (): void => {
         let result: ExecutionResult;
 
-        exec_loop:
+        exec_loop: while (true) {
-        while (true) {
             result = this.vm.execute();
 
             const srcloc = this.vm.get_current_source_location();
-            if (srcloc && asm_editor_store.breakpoints.val.includes(srcloc.line_no)) {
+            if (srcloc) {
-                asm_editor_store.set_execution_location(srcloc.line_no);
+                const hit_breakpoint =
-                break exec_loop;
+                    this.break_on_next ||
+                    asm_editor_store.breakpoints.val.includes(srcloc.line_no) ||
+                    this.stepping_breakpoints.includes(srcloc.line_no);
+                if (hit_breakpoint) {
+                    this.stepping_breakpoints.length = 0;
+                    asm_editor_store.set_execution_location(srcloc.line_no);
+                    break exec_loop;
+                }
             }
 
+            this.break_on_next = false;
+
             switch (result) {
                 case ExecutionResult.WaitingVsync:
                     this.vm.vsync();
@@ -99,4 +183,34 @@ export class QuestRunner {
             },
         };
     };
+
+    private get_instruction_segment_by_index(index: number): InstructionSegment {
+        defined(this.quest);
+
+        const segment = this.quest.object_code[index];
+
+        assert(
+            segment.type === SegmentType.Instructions,
+            `Expected segment ${index} to be of type ${
+                SegmentType[SegmentType.Instructions]
+            }, but was ${SegmentType[segment.type]}.`,
+        );
+
+        return segment;
+    }
+
+    private get_instruction_segment_by_label(label: number): InstructionSegment {
+        const seg_idx = this.vm.get_segment_index_by_label(label);
+        return this.get_instruction_segment_by_index(seg_idx);
+    }
+
+    private get_step_innable_instruction_label_argument(instr: Instruction): number | undefined {
+        switch (instr.opcode.code) {
+            case OP_VA_CALL.code:
+            case OP_CALL.code:
+                return instr.args[0].value;
+            case OP_SWITCH_CALL.code:
+                return instr.args[1].value;
+        }
+    }
 }

src/quest_editor/scripting/vm/index.ts

@@ -661,7 +661,7 @@ export class VirtualMachine {
 
                 this.set_episode_called = true;
 
-                if (this.get_current_segment_idx() !== ENTRY_SEGMENT) {
+                if (this.get_current_execution_location().seg_idx !== ENTRY_SEGMENT) {
                     this.io.warning(
                         `Calling set_episode outside of segment ${ENTRY_SEGMENT} is not supported.`,
                         srcloc,
@@ -1000,8 +1000,8 @@ export class VirtualMachine {
         return str;
     }
 
-    private get_current_segment_idx(): number {
+    public get_current_execution_location(): Readonly<ExecutionLocation> {
-        return this.thread[this.thread_idx].call_stack_top().seg_idx;
+        return this.thread[this.thread_idx].call_stack_top();
     }
 
     private missing_quest_data_warning(info: string, srcloc?: AsmToken): void {
@@ -1154,7 +1154,7 @@ export class VirtualMachine {
     }
 }
 
-class ExecutionLocation {
+export class ExecutionLocation {
     constructor(public seg_idx: number, public inst_idx: number) {}
 }