69 lines
1.9 KiB
PHP
69 lines
1.9 KiB
PHP
<?php
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namespace App\Services;
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use App\Exceptions\PromptRenderException;
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use RuntimeException;
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/**
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* Pure prompt template renderer. No framework dependencies.
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*
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* Variable syntax: `{{ name }}` where name matches `[A-Za-z0-9_-]+`.
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* Rendering is strict: it throws PromptRenderException when any variable
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* lacks a string value. Values are inserted verbatim, in a single pass
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* (inserted values are never re-scanned for variables).
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*/
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class PromptRenderer
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{
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public const VARIABLE_PATTERN = '/\{\{\s*([A-Za-z0-9_-]+)\s*\}\}/';
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/**
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* Extract the unique variable names in first-occurrence order.
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*
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* @return list<string>
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*/
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public function extractVariables(string $body): array
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{
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if (preg_match_all(self::VARIABLE_PATTERN, $body, $matches) === false) {
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return [];
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}
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return array_values(array_unique($matches[1]));
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}
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/**
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* Render the template with the given values.
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*
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* @param array<string, mixed> $values
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*
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* @throws PromptRenderException when any variable has no string value
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* @throws RuntimeException when the template cannot be processed
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*/
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public function render(string $body, array $values): string
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{
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$missing = [];
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foreach ($this->extractVariables($body) as $variable) {
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if (! array_key_exists($variable, $values) || ! is_string($values[$variable])) {
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$missing[] = $variable;
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}
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}
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if ($missing !== []) {
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throw PromptRenderException::missing($missing);
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}
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$rendered = preg_replace_callback(
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self::VARIABLE_PATTERN,
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static fn (array $matches): string => (string) ($values[$matches[1]] ?? $matches[0]),
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$body
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);
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if ($rendered === null) {
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throw new RuntimeException('Prompt template could not be rendered.');
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}
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return $rendered;
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}
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}
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