Adding Support Mod Parsers

Adding Support Mod Parsers

Overview

Support mod parsers convert raw support skill affix strings (e.g., "+15% additional damage for the supported skill") into typed SupportMod objects at runtime. Unlike active/passive skills which use level-scaling factories, support skills parse their affixes directly using templates.

When to Use

• Adding support for new support skill affix patterns
• Extending support mod parsing to handle new variants

Project File Locations

Implementation Checklist

1. Check if Mod Type Exists

Look in src/tli/mod.ts under ModDefinitions. If the mod type doesn't exist, add it first (see adding-mod-parsers skill).

2. Add Template in support-mod-templates.ts

Templates use the same DSL as the main mod parser:

// In allSupportParsers array
t("{value:dec%} additional damage for the supported skill").output(
  "DmgPct",
  (c) => ({
    value: c.value,
    dmgModType: "global" as const,
    addn: true,
  }),
),

Template capture types:

Signed vs Unsigned Types:

• Use unsigned (dec%, int) when input does NOT start with + or - (e.g., "0.8% additional damage")
• Use signed (+dec%, +int) when input STARTS with + or - (e.g., "+19.8% additional damage")
• Signed types will NOT match unsigned inputs, and vice versa
• IMPORTANT: Some support skills have signed inputs, others have unsigned - you may need BOTH templates (see examples below)

Optional syntax:

• [additional] - Optional literal, sets c.additional?: true
• (effect|damage) - Alternation (regex-style)
• \\( and \\) - Escaped parentheses for literal matching

3. SupportMod Structure

Each parsed mod is wrapped in SupportMod:

interface SupportMod {
  mod: Mod;
}

The parseSupportAffix function handles this wrapping:

return mods.map((mod) => ({ mod }));

4. Multi-Output Parsers

For affixes that produce multiple mods:

t("{value:dec%} additional attack and cast speed for the supported skill")
  .outputMany([
    spec("AspdPct", (c) => ({ value: c.value, addn: true })),
    spec("CspdPct", (c) => ({ value: c.value, addn: true })),
  ]),

5. Add a Test

Add a test case to src/tli/skills/support-mod-templates.test.ts using the example input string given to you:

test("parse <skill name> <description of what it parses>", () => {
  const result = parseSupportAffixes([
    "<exact input string from the skill data>",
  ]);
  expect(result).toEqual([
    [
      {
        mod: {
          type: "<ModType>",
          // ... expected mod properties
        },
      },
    ],
  ]);
});

6. Verify

Run tests to ensure parsing works:

pnpm test
pnpm typecheck
pnpm check

Examples

Damage Mod with BOTH Signed and Unsigned Variants

Some support skills use +{value}% templates (e.g., Increased Area) while others use {value}% (e.g., Haunt). You need BOTH templates:

Inputs:

• "+19.8% additional damage for the supported skill" (Increased Area - signed)
• "0.8% additional damage for the supported skill" (Haunt - unsigned)

// Signed version (e.g., "+19.8% additional damage...")
t("{value:+dec%} additional damage for the supported skill").output(
  "DmgPct",
  (c) => ({
    value: c.value,
    dmgModType: "global" as const,
    addn: true,
  }),
),
// Unsigned version (e.g., "0.8% additional damage...")
t("{value:dec%} additional damage for the supported skill").output(
  "DmgPct",
  (c) => ({
    value: c.value,
    dmgModType: "global" as const,
    addn: true,
  }),
),

Typed Damage Mod (Signed)

Input: "+20% additional melee damage for the supported skill"

t("{value:+dec%} additional melee damage for the supported skill").output(
  "DmgPct",
  (c) => ({
    value: c.value,
    dmgModType: "melee" as const,
    addn: true,
  }),
),

Attack Speed (Signed - can be negative)

Input: "-15% Attack Speed for the supported skill" (Steamroll)

t("{value:+dec%} attack speed for the supported skill").output(
  "AspdPct",
  (c) => ({
    value: c.value,
    addn: false,
  }),
),

Note: +dec% matches both + and - signs.

Conditional Mod

Input: "The supported skill deals +30% additional damage to cursed enemies"

t("the supported skill deals {value:dec%} additional damage to cursed enemies")
  .output("DmgPct", (c) => ({
    value: c.value,
    dmgModType: "global" as const,
    addn: true,
    cond: "enemy_is_cursed" as const,
  })),

Per-Stackable Mod

Input: "+5% additional damage for the supported skill for every stack of buffs while standing still"

t("{value:dec%} additional damage for the supported skill for every stack of buffs while standing still")
  .output("DmgPct", (c) => ({
    value: c.value,
    dmgModType: "global" as const,
    addn: false,
    per: { stackable: "willpower" as const },
  })),

Mod with No Value

Input: "The supported skill cannot inflict wilt"

t("the supported skill cannot inflict wilt").output("CannotInflictWilt"),

Escaped Parentheses

Input: "Stacks up to 5 time(s)"

t("stacks up to {value:int} time(s)").output("MaxWillpowerStacks", (c) => ({
  value: c.value,
})),

Note: Literal ( and ) don't need escaping when they don't contain alternations.

Complex Pattern with Ignored Values

Input: "When the supported skill deals damage over time, it inflicts 10 affliction on the enemy. Effect cooldown: 3 s"

t("when the supported skill deals damage over time, it inflicts {value:int} affliction on the enemy. effect cooldown: {_:int} s")
  .output("AfflictionInflictedPerSec", (c) => ({
    value: c.value,
  })),

Use {_:type} to capture but ignore values.

Shadow Quantity (Signed Flat Integer)

Input: "+2 Shadow Quantity for the supported skill"

t("{value:+int} shadow quantity for the supported skill").output(
  "ShadowQuant",
  (c) => ({
    value: c.value,
  }),
),

Template Ordering

IMPORTANT: More specific patterns must come before generic ones in allSupportParsers array.

// Good: specific before generic
t("{value:dec%} additional melee damage for the supported skill").output(...),
t("{value:dec%} additional damage for the supported skill").output(...),

// Bad: generic would match first
t("{value:dec%} additional damage for the supported skill").output(...),
t("{value:dec%} additional melee damage for the supported skill").output(...),  // never matches

Common Mistakes

Data Flow

Support skill affix: "+15% additional damage for the supported skill"
    ↓ parseSupportAffixes()
    ↓ normalize (lowercase, trim)
"15% additional damage for the supported skill"
    ↓ template matching (allSupportParsers)
[{ mod: { type: "DmgPct", value: 15, dmgModType: "global", addn: true } }]
    ↓ resolveSelectedSkillSupportMods() in offense.ts
Applied to skill calculations

Difference from Main Mod Parser

Both use the same template DSL (t(), spec(), outputMany()).