# Dynamic Token Interpolation

To deliver personalized interactions, **Asterisk 2** implements real-time prompt interpolation logic. The engine parses variable template strings prior to converting textual content into spoken output files.

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## String Replacement Processing Architecture

The flow block below illustrates how raw string blueprints convert into compiled voice scripts:

```mermaid
graph TD
    %% Base Template
    subgraph TemplateSource["Configured Prompt String"]
        RawString["Unparsed Layout String<br/>('Hello ${first_name}, your balance is ${amt}')"]
    end

    %% Token Resolution
    subgraph InterpolatorEngine["Regex Token Engine"]
        MatchTokens["Extract Target Keys<br/>(Identifies: first_name, amt)"]
        FetchCache["Query Current Call Memory<br/>(Fetches: 'Sandeep', '500')"]
    end

    %% Final Payload
    subgraph ExecutedPayload["Output Audio Generator"]
        CompiledAudio["Text-to-Speech Engine<br/>('Hello Sandeep, your balance is 500')"]
    end

    %% Links
    RawString ==>|"Pass Raw Template"| MatchTokens
    MatchTokens --> FetchCache
    FetchCache ==>|"Inject Interpolated String"| CompiledAudio

    %% High-Fidelity Custom Themes
    classDef srcToken fill:#0f172a,stroke:#38bdf8,stroke-width:2px,color:#fff,rx:6px,ry:6px;
    classDef engToken fill:#1e293b,stroke:#a855f7,stroke-width:2px,color:#fff,rx:6px,ry:6px;
    classDef targetToken fill:#065f46,stroke:#10b981,stroke-width:2px,color:#fff,rx:6px,ry:6px;

    class TemplateSource,RawString srcToken;
    class InterpolatorEngine,MatchTokens,FetchCache engToken;
    class ExecutedPayload,CompiledAudio targetToken;
```

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## Interpolation Process Rules

### 1. Missing Token Clamping
If custom text blocks reference parameter names completely absent from operational call memory stores, formatting engines fallback to empty string assignments instantly (`""`), completely preventing text synthesis engines from reading out raw bracket syntax characters.

### 2. Nested Token Expansions
String processing pipelines run recursive replacement sweeps up to three nested configuration depth levels, supporting structured variable building operations cleanly.