feat(#3): Add PDF caching

2025-12-23 10:09:30 +01:00
parent 9999ac3bb4
commit 4dfa62fcfe
16 changed files with 469 additions and 37 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -67,3 +67,6 @@ legalconsenthub-backend/postgres-data/
 ### Docker BuildKit cache ###
 .buildx-cache/

+### Version PDF cache (dev) ###
+legalconsenthub-backend/.pdf-store/
+
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -134,7 +134,7 @@ Forms can be exported as:

 Endpoints:
 - `GET /application-forms/{id}/html` - Returns HTML representation
- `GET /application-forms/{id}/pdf` - Returns PDF (inline display)
+- `GET /application-forms/{id}/versions/{versionNumber}/pdf` - Returns version PDF (inline display)

 ### 6. Comments System

@@ -585,7 +585,7 @@ Migrations are managed manually using **Liquibase** in `src/main/resources/db/ch
 - `GET /application-forms/{id}` - Get form by ID
 - `PUT /application-forms/{id}` - Update form
 - `DELETE /application-forms/{id}` - Delete form
- `GET /application-forms/{id}/pdf` - Export as PDF
+- `GET /application-forms/{id}/versions/{versionNumber}/pdf` - Export a version as PDF
 - `GET /application-forms/{id}/html` - Export as HTML
 - `POST /application-forms/{id}/submit` - Submit form
 - `POST /application-forms/{applicationFormId}/subsections/{subsectionId}/form-elements?position={n}` - Add form element dynamically
@@ -741,7 +741,7 @@ act -n
   - Any change that touches form element types, options/value storage, visibility conditions, or section spawning can break PDF output.
   - Always validate **both** HTML and PDF export for a real form instance (including newly spawned sections and newly added text fields with values):
     - `GET /application-forms/{id}/html`
-     - `GET /application-forms/{id}/pdf`
+     - `GET /application-forms/{id}/versions/{versionNumber}/pdf`
   - Verify these render correctly (with saved values):
     - `TEXTFIELD`, `TEXTAREA`, `DATE`, `RICH_TEXT`
     - `SELECT`, `RADIOBUTTON`, `CHECKBOX`, `SWITCH`
--- a/api/legalconsenthub.yml
+++ b/api/legalconsenthub.yml
@@ -134,12 +134,12 @@ paths:
        "503":
          $ref: "https://api.swaggerhub.com/domains/smartbear-public/ProblemDetails/1.0.0#/components/responses/ServiceUnavailable"

-  /application-forms/{id}/pdf:
+  /application-forms/{id}/versions/{versionNumber}/pdf:
    get:
-      summary: Returns the application form rendered as PDF
-      operationId: getApplicationFormPdf
+      summary: Returns the application form version rendered as PDF
+      operationId: getApplicationFormVersionPdf
      tags:
-        - application-form
+        - application-form-version
      parameters:
        - name: id
          in: path
@@ -147,9 +147,15 @@ paths:
          schema:
            type: string
            format: uuid
+        - name: versionNumber
+          in: path
+          required: true
+          schema:
+            type: integer
+            format: int32
      responses:
        '200':
-          description: Application form as PDF
+          description: Application form version as PDF
          content:
            application/pdf:
              schema:
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form/ApplicationFormController.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form/ApplicationFormController.kt
@@ -4,10 +4,6 @@ import com.betriebsratkanzlei.legalconsenthub_api.api.ApplicationFormApi
 import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormDto
 import com.betriebsratkanzlei.legalconsenthub_api.model.FormElementDto
 import com.betriebsratkanzlei.legalconsenthub_api.model.PagedApplicationFormDto
-import org.springframework.core.io.ByteArrayResource
-import org.springframework.core.io.Resource
-import org.springframework.http.HttpHeaders
-import org.springframework.http.MediaType
 import org.springframework.http.ResponseEntity
 import org.springframework.security.access.prepost.PreAuthorize
 import org.springframework.web.bind.annotation.RestController
@@ -62,20 +58,6 @@ class ApplicationFormController(
        )
    }

-    @PreAuthorize(
-        "hasAnyRole('CHIEF_EXECUTIVE_OFFICER', 'BUSINESS_DEPARTMENT', 'IT_DEPARTMENT', 'HUMAN_RESOURCES', 'HEAD_OF_WORKS_COUNCIL', 'WORKS_COUNCIL', 'EMPLOYEE')",
-    )
-    override fun getApplicationFormPdf(id: UUID): ResponseEntity<Resource> {
-        val applicationForm = applicationFormService.getApplicationFormById(id)
-        val pdfBytes = applicationFormFormatService.generatePdf(applicationForm)
-        val resource = ByteArrayResource(pdfBytes)
-        return ResponseEntity
-            .ok()
-            .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"form-$id.pdf\"")
-            .contentType(MediaType.APPLICATION_PDF)
-            .body(resource)
-    }
-
    @PreAuthorize(
        "hasAnyRole('CHIEF_EXECUTIVE_OFFICER', 'BUSINESS_DEPARTMENT', 'IT_DEPARTMENT', 'HUMAN_RESOURCES', 'HEAD_OF_WORKS_COUNCIL', 'WORKS_COUNCIL')",
    )
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form/ApplicationFormFormatService.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form/ApplicationFormFormatService.kt
@@ -12,12 +12,19 @@ import com.betriebsratkanzlei.legalconsenthub.form_element.FormElementSection
 import com.betriebsratkanzlei.legalconsenthub.form_element.FormElementSubSection
 import com.betriebsratkanzlei.legalconsenthub.form_element.VisibilityConditionOperator
 import com.betriebsratkanzlei.legalconsenthub.form_element.VisibilityConditionType
+import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormSnapshotDto
+import com.betriebsratkanzlei.legalconsenthub_api.model.FormElementSectionSnapshotDto
+import com.betriebsratkanzlei.legalconsenthub_api.model.FormElementSnapshotDto
+import com.betriebsratkanzlei.legalconsenthub_api.model.FormElementSubSectionSnapshotDto
 import org.springframework.stereotype.Service
 import org.thymeleaf.TemplateEngine
 import org.thymeleaf.context.Context
 import java.time.LocalDate
+import java.time.LocalDateTime
 import java.time.format.DateTimeFormatter
 import java.util.UUID
+import com.betriebsratkanzlei.legalconsenthub_api.model.VisibilityConditionOperator as VisibilityConditionOperatorDto
+import com.betriebsratkanzlei.legalconsenthub_api.model.VisibilityConditionType as VisibilityConditionTypeDto

@Service
 class ApplicationFormFormatService(
@@ -30,6 +37,14 @@ class ApplicationFormFormatService(
        return pdfRenderer.render(latexContent)
    }

+    fun generatePdf(
+        snapshot: ApplicationFormSnapshotDto,
+        createdAt: LocalDateTime?,
+    ): ByteArray {
+        val latexContent = generateLatex(snapshot, createdAt)
+        return pdfRenderer.render(latexContent)
+    }
+
    fun generateLatex(applicationForm: ApplicationForm): String {
        val filteredForm = filterVisibleElements(applicationForm)
        val exportModel = buildLatexExportModel(filteredForm)
@@ -41,6 +56,20 @@ class ApplicationFormFormatService(
        return templateEngine.process("application_form_latex_template", context)
    }

+    fun generateLatex(
+        snapshot: ApplicationFormSnapshotDto,
+        createdAt: LocalDateTime?,
+    ): String {
+        val filteredSnapshot = filterVisibleElements(snapshot)
+        val exportModel = buildLatexExportModel(filteredSnapshot, createdAt)
+
+        val context =
+            Context().apply {
+                setVariable("applicationForm", exportModel)
+            }
+        return templateEngine.process("application_form_latex_template", context)
+    }
+
    fun generateHtml(applicationForm: ApplicationForm): String {
        val filteredForm = filterVisibleElements(applicationForm)
        val context =
@@ -85,6 +114,44 @@ class ApplicationFormFormatService(
        )
    }

+    private fun buildLatexExportModel(
+        snapshot: ApplicationFormSnapshotDto,
+        createdAt: LocalDateTime?,
+    ): LatexExportModel {
+        val dateFormatter = DateTimeFormatter.ofPattern("dd.MM.yyyy")
+
+        return LatexExportModel(
+            id = null,
+            name = LatexEscaper.escape(snapshot.name),
+            organizationId = LatexEscaper.escape(snapshot.organizationId),
+            employer = LatexEscaper.escape("Arbeitgeber der Organisation ${snapshot.organizationId}"),
+            worksCouncil = LatexEscaper.escape("Betriebsrat der Organisation ${snapshot.organizationId}"),
+            createdAt = createdAt?.format(dateFormatter) ?: "",
+            sections =
+                snapshot.sections.map { section ->
+                    LatexSection(
+                        title = LatexEscaper.escape(section.title),
+                        description = LatexEscaper.escape(section.description ?: ""),
+                        subsections =
+                            section.subsections.map { subsection ->
+                                LatexSubSection(
+                                    title = LatexEscaper.escape(subsection.title),
+                                    subtitle = LatexEscaper.escape(subsection.subtitle ?: ""),
+                                    elements =
+                                        subsection.elements.map { element ->
+                                            LatexFormElement(
+                                                title = LatexEscaper.escape(element.title ?: ""),
+                                                description = LatexEscaper.escape(element.description ?: ""),
+                                                value = renderElementValue(element),
+                                            )
+                                        },
+                                )
+                            },
+                    )
+                },
+        )
+    }
+
    private fun renderElementValue(element: FormElement): String =
        when (element.type.name) {
            "TEXTFIELD", "TEXTAREA" -> {
@@ -127,6 +194,48 @@ class ApplicationFormFormatService(
            else -> "Keine Auswahl getroffen"
        }

+    private fun renderElementValue(element: FormElementSnapshotDto): String =
+        when (element.type.name) {
+            "TEXTFIELD", "TEXTAREA" -> {
+                val value = element.options.firstOrNull()?.value
+                if (value.isNullOrBlank()) "Keine Eingabe" else LatexEscaper.escape(value)
+            }
+            "DATE" -> {
+                val value = element.options.firstOrNull()?.value
+                if (value.isNullOrBlank()) {
+                    "Kein Datum ausgewählt"
+                } else {
+                    try {
+                        LocalDate.parse(value).format(DateTimeFormatter.ofPattern("dd.MM.yyyy"))
+                    } catch (e: Exception) {
+                        LatexEscaper.escape(value)
+                    }
+                }
+            }
+            "RICH_TEXT" -> {
+                val value = element.options.firstOrNull()?.value
+                if (value.isNullOrBlank()) "Keine Eingabe" else richTextToLatexConverter.convertToLatex(value)
+            }
+            "SELECT", "CHECKBOX" -> {
+                val selected = element.options.filter { it.value == "true" }.map { it.label }
+                if (selected.isEmpty()) {
+                    "Keine Auswahl getroffen"
+                } else {
+                    selected.joinToString(
+                        ", ",
+                    ) { LatexEscaper.escape(it) }
+                }
+            }
+            "RADIOBUTTON" -> {
+                val selected = element.options.firstOrNull { it.value == "true" }?.label
+                if (selected == null) "Keine Auswahl getroffen" else LatexEscaper.escape(selected)
+            }
+            "SWITCH" -> {
+                if (element.options.any { it.value == "true" }) "Ja" else "Nein"
+            }
+            else -> "Keine Auswahl getroffen"
+        }
+
    private fun filterVisibleElements(applicationForm: ApplicationForm): ApplicationForm {
        val allElements = collectAllFormElements(applicationForm)
        val formElementsByRef = buildFormElementsByRefMap(allElements)
@@ -187,16 +296,50 @@ class ApplicationFormFormatService(
        )
    }

+    private fun filterVisibleElements(snapshot: ApplicationFormSnapshotDto): ApplicationFormSnapshotDto {
+        val allElements = collectAllFormElements(snapshot)
+        val formElementsByRef = buildSnapshotFormElementsByRefMap(allElements)
+
+        val filteredSections =
+            snapshot.sections
+                .filter { it.isTemplate != true }
+                .mapNotNull { section ->
+                    val filteredSubsections =
+                        section.subsections.mapNotNull { subsection ->
+                            val filteredElements =
+                                subsection.elements.filter { element ->
+                                    isElementVisible(element, formElementsByRef)
+                                }
+                            if (filteredElements.isEmpty()) null else subsection.copy(elements = filteredElements)
+                        }
+                    if (filteredSubsections.isEmpty()) null else section.copy(subsections = filteredSubsections)
+                }
+
+        return snapshot.copy(sections = filteredSections)
+    }
+
    private fun collectAllFormElements(applicationForm: ApplicationForm): List<FormElement> =
        applicationForm.formElementSections
            .flatMap { it.formElementSubSections }
            .flatMap { it.formElements }

+    private fun collectAllFormElements(snapshot: ApplicationFormSnapshotDto): List<FormElementSnapshotDto> =
+        snapshot.sections
+            .flatMap(FormElementSectionSnapshotDto::subsections)
+            .flatMap(FormElementSubSectionSnapshotDto::elements)
+
    private fun buildFormElementsByRefMap(allElements: List<FormElement>): Map<String, FormElement> =
        allElements
            .mapNotNull { elem -> elem.reference?.let { it to elem } }
            .toMap()

+    private fun buildSnapshotFormElementsByRefMap(
+        allElements: List<FormElementSnapshotDto>,
+    ): Map<String, FormElementSnapshotDto> =
+        allElements
+            .mapNotNull { elem -> elem.reference?.let { it to elem } }
+            .toMap()
+
    private fun evaluateVisibility(
        allElements: List<FormElement>,
        formElementsByRef: Map<String, FormElement>,
@@ -229,6 +372,24 @@ class ApplicationFormFormatService(
        }
    }

+    private fun isElementVisible(
+        element: FormElementSnapshotDto,
+        formElementsByRef: Map<String, FormElementSnapshotDto>,
+    ): Boolean {
+        val condition = element.visibilityCondition ?: return true
+
+        val sourceElement = formElementsByRef[condition.sourceFormElementReference] ?: return false
+        val sourceValue = getFormElementValue(sourceElement)
+
+        val operator = condition.formElementOperator ?: VisibilityConditionOperatorDto.EQUALS
+        val conditionMet = evaluateCondition(sourceValue, condition.formElementExpectedValue, operator)
+
+        return when (condition.formElementConditionType) {
+            VisibilityConditionTypeDto.SHOW -> conditionMet
+            VisibilityConditionTypeDto.HIDE -> !conditionMet
+        }
+    }
+
    private fun getFormElementValue(element: FormElement): String =
        when (element.type.name) {
            "SELECT",
@@ -240,6 +401,17 @@ class ApplicationFormFormatService(
            else -> element.options.firstOrNull()?.value ?: ""
        }

+    private fun getFormElementValue(element: FormElementSnapshotDto): String =
+        when (element.type.name) {
+            "SELECT",
+            "RADIOBUTTON",
+            -> element.options.firstOrNull { it.value == "true" }?.label ?: ""
+            "CHECKBOX",
+            "SWITCH",
+            -> if (element.options.any { it.value == "true" }) "true" else "false"
+            else -> element.options.firstOrNull()?.value ?: ""
+        }
+
    private fun evaluateCondition(
        actualValue: String,
        expectedValue: String,
@@ -251,4 +423,16 @@ class ApplicationFormFormatService(
            VisibilityConditionOperator.IS_EMPTY -> actualValue.isEmpty()
            VisibilityConditionOperator.IS_NOT_EMPTY -> actualValue.isNotEmpty()
        }
+
+    private fun evaluateCondition(
+        actualValue: String,
+        expectedValue: String,
+        operator: VisibilityConditionOperatorDto,
+    ): Boolean =
+        when (operator) {
+            VisibilityConditionOperatorDto.EQUALS -> actualValue.equals(expectedValue, ignoreCase = true)
+            VisibilityConditionOperatorDto.NOT_EQUALS -> !actualValue.equals(expectedValue, ignoreCase = true)
+            VisibilityConditionOperatorDto.IS_EMPTY -> actualValue.isEmpty()
+            VisibilityConditionOperatorDto.IS_NOT_EMPTY -> actualValue.isNotEmpty()
+        }
 }
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/ApplicationFormVersionController.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/ApplicationFormVersionController.kt
@@ -1,11 +1,16 @@
 package com.betriebsratkanzlei.legalconsenthub.application_form_version

 import com.betriebsratkanzlei.legalconsenthub.application_form.ApplicationFormMapper
+import com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf.ApplicationFormVersionPdfService
 import com.betriebsratkanzlei.legalconsenthub.user.UserService
 import com.betriebsratkanzlei.legalconsenthub_api.api.ApplicationFormVersionApi
 import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormDto
 import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormVersionDto
 import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormVersionListItemDto
+import org.springframework.core.io.ByteArrayResource
+import org.springframework.core.io.Resource
+import org.springframework.http.HttpHeaders
+import org.springframework.http.MediaType
 import org.springframework.http.ResponseEntity
 import org.springframework.security.access.prepost.PreAuthorize
 import org.springframework.web.bind.annotation.RestController
@@ -17,6 +22,7 @@ class ApplicationFormVersionController(
    private val versionMapper: ApplicationFormVersionMapper,
    private val applicationFormMapper: ApplicationFormMapper,
    private val userService: UserService,
+    private val versionPdfService: ApplicationFormVersionPdfService,
 ) : ApplicationFormVersionApi {
    @PreAuthorize(
        "hasAnyRole('CHIEF_EXECUTIVE_OFFICER', 'BUSINESS_DEPARTMENT', 'IT_DEPARTMENT', 'HUMAN_RESOURCES', 'HEAD_OF_WORKS_COUNCIL', 'WORKS_COUNCIL', 'EMPLOYEE')",
@@ -37,6 +43,22 @@ class ApplicationFormVersionController(
        return ResponseEntity.ok(versionMapper.toApplicationFormVersionDto(version))
    }

+    @PreAuthorize(
+        "hasAnyRole('CHIEF_EXECUTIVE_OFFICER', 'BUSINESS_DEPARTMENT', 'IT_DEPARTMENT', 'HUMAN_RESOURCES', 'HEAD_OF_WORKS_COUNCIL', 'WORKS_COUNCIL', 'EMPLOYEE')",
+    )
+    override fun getApplicationFormVersionPdf(
+        id: UUID,
+        versionNumber: Int,
+    ): ResponseEntity<Resource> {
+        val pdfBytes = versionPdfService.getOrGeneratePdf(id, versionNumber)
+        val resource = ByteArrayResource(pdfBytes)
+        return ResponseEntity
+            .ok()
+            .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"form-$id-v$versionNumber.pdf\"")
+            .contentType(MediaType.APPLICATION_PDF)
+            .body(resource)
+    }
+
    @PreAuthorize(
        "hasAnyRole('CHIEF_EXECUTIVE_OFFICER', 'BUSINESS_DEPARTMENT', 'IT_DEPARTMENT', 'HUMAN_RESOURCES', 'HEAD_OF_WORKS_COUNCIL', 'WORKS_COUNCIL')",
    )
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/ApplicationFormVersionService.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/ApplicationFormVersionService.kt
@@ -7,6 +7,7 @@ import com.betriebsratkanzlei.legalconsenthub.error.ApplicationFormVersionNotFou
 import com.betriebsratkanzlei.legalconsenthub.form_element.FormElement
 import com.betriebsratkanzlei.legalconsenthub.form_element.FormElementSection
 import com.betriebsratkanzlei.legalconsenthub.form_element.FormElementSubSection
+import com.betriebsratkanzlei.legalconsenthub.form_element.FormElementVisibilityConditionMapper
 import com.betriebsratkanzlei.legalconsenthub.form_element.FormOption
 import com.betriebsratkanzlei.legalconsenthub.form_element.SectionSpawnTriggerMapper
 import com.betriebsratkanzlei.legalconsenthub.user.User
@@ -26,6 +27,7 @@ class ApplicationFormVersionService(
    private val applicationFormRepository: ApplicationFormRepository,
    private val objectMapper: ObjectMapper,
    private val spawnTriggerMapper: SectionSpawnTriggerMapper,
+    private val visibilityConditionMapper: FormElementVisibilityConditionMapper,
 ) {
    @Transactional
    fun createVersion(
@@ -130,6 +132,12 @@ class ApplicationFormVersionService(
                                                            employeeDataCategory = option.employeeDataCategory,
                                                        )
                                                    },
+                                                visibilityCondition =
+                                                    element.visibilityCondition?.let {
+                                                        visibilityConditionMapper.toFormElementVisibilityConditionDto(
+                                                            it,
+                                                        )
+                                                    },
                                                sectionSpawnTrigger =
                                                    element.sectionSpawnTrigger?.let {
                                                        spawnTriggerMapper.toSectionSpawnTriggerDto(it)
@@ -185,6 +193,10 @@ class ApplicationFormVersionService(
                                        employeeDataCategory = optionDto.employeeDataCategory,
                                    )
                                }.toMutableList(),
+                        visibilityCondition =
+                            elementSnapshot.visibilityCondition?.let {
+                                visibilityConditionMapper.toFormElementVisibilityCondition(it)
+                            },
                        sectionSpawnTrigger =
                            elementSnapshot.sectionSpawnTrigger?.let {
                                spawnTriggerMapper.toSectionSpawnTrigger(it)
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/ApplicationFormVersionPdfService.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/ApplicationFormVersionPdfService.kt
@@ -0,0 +1,61 @@
+package com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf
+
+import com.betriebsratkanzlei.legalconsenthub.application_form.ApplicationFormFormatService
+import com.betriebsratkanzlei.legalconsenthub.application_form_version.ApplicationFormVersionService
+import com.betriebsratkanzlei.legalconsenthub_api.model.ApplicationFormSnapshotDto
+import com.fasterxml.jackson.databind.ObjectMapper
+import org.slf4j.LoggerFactory
+import org.springframework.stereotype.Service
+import java.util.UUID
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.locks.ReentrantLock
+
+@Service
+class ApplicationFormVersionPdfService(
+    private val versionService: ApplicationFormVersionService,
+    private val objectMapper: ObjectMapper,
+    private val formatService: ApplicationFormFormatService,
+    private val pdfStorage: PdfStorage,
+) {
+    private val logger = LoggerFactory.getLogger(ApplicationFormVersionPdfService::class.java)
+    private val locks = ConcurrentHashMap<PdfStorageKey, ReentrantLock>()
+
+    fun getOrGeneratePdf(
+        applicationFormId: UUID,
+        versionNumber: Int,
+    ): ByteArray {
+        val version = versionService.getVersion(applicationFormId, versionNumber)
+        val key = PdfStorageKey(applicationFormId, versionNumber)
+
+        pdfStorage.get(key)?.let {
+            logger.debug(
+                "Serving cached version PDF: applicationFormId={} version={}",
+                applicationFormId,
+                versionNumber,
+            )
+            return it
+        }
+
+        val lock = locks.computeIfAbsent(key) { ReentrantLock() }
+        lock.lock()
+        try {
+            pdfStorage.get(key)?.let {
+                logger.debug(
+                    "Serving cached version PDF after lock: applicationFormId={} version={}",
+                    applicationFormId,
+                    versionNumber,
+                )
+                return it
+            }
+
+            logger.info("Generating version PDF: applicationFormId=$applicationFormId version=$versionNumber")
+            val snapshot = objectMapper.readValue(version.snapshotData, ApplicationFormSnapshotDto::class.java)
+            val pdfBytes = formatService.generatePdf(snapshot, version.createdAt)
+
+            pdfStorage.put(key, pdfBytes)
+            return pdfBytes
+        } finally {
+            lock.unlock()
+        }
+    }
+}
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/FileSystemPdfStorage.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/FileSystemPdfStorage.kt
@@ -0,0 +1,61 @@
+package com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf
+
+import org.slf4j.LoggerFactory
+import org.springframework.stereotype.Component
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.StandardCopyOption
+import kotlin.io.path.exists
+import kotlin.io.path.inputStream
+
+@Component
+class FileSystemPdfStorage(
+    private val properties: PdfStorageProperties,
+) : PdfStorage {
+    private val logger = LoggerFactory.getLogger(FileSystemPdfStorage::class.java)
+
+    override fun get(key: PdfStorageKey): ByteArray? {
+        val path = resolvePath(key)
+        if (!path.exists()) return null
+        return path.inputStream().use { it.readBytes() }
+    }
+
+    override fun put(
+        key: PdfStorageKey,
+        bytes: ByteArray,
+    ) {
+        val targetPath = resolvePath(key)
+        Files.createDirectories(targetPath.parent)
+
+        val tmpFile = Files.createTempFile(targetPath.parent, targetPath.fileName.toString(), ".tmp")
+        try {
+            Files.write(tmpFile, bytes)
+            try {
+                Files.move(
+                    tmpFile,
+                    targetPath,
+                    StandardCopyOption.ATOMIC_MOVE,
+                    StandardCopyOption.REPLACE_EXISTING,
+                )
+            } catch (e: Exception) {
+                logger.debug("Atomic move failed, falling back to non-atomic move: ${e.message}")
+                Files.move(
+                    tmpFile,
+                    targetPath,
+                    StandardCopyOption.REPLACE_EXISTING,
+                )
+            }
+        } finally {
+            try {
+                Files.deleteIfExists(tmpFile)
+            } catch (_: Exception) {
+                // ignore
+            }
+        }
+    }
+
+    private fun resolvePath(key: PdfStorageKey): Path {
+        val baseDir = Path.of(properties.filesystem.baseDir)
+        return key.toPathParts().fold(baseDir) { acc, part -> acc.resolve(part) }
+    }
+}
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorage.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorage.kt
@@ -0,0 +1,10 @@
+package com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf
+
+interface PdfStorage {
+    fun get(key: PdfStorageKey): ByteArray?
+
+    fun put(
+        key: PdfStorageKey,
+        bytes: ByteArray,
+    )
+}
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorageKey.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorageKey.kt
@@ -0,0 +1,14 @@
+package com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf
+
+import java.util.UUID
+
+data class PdfStorageKey(
+    val applicationFormId: UUID,
+    val versionNumber: Int,
+) {
+    fun toPathParts(): List<String> =
+        listOf(
+            applicationFormId.toString(),
+            "v$versionNumber.pdf",
+        )
+}
--- a/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorageProperties.kt
+++ b/legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/application_form_version/pdf/PdfStorageProperties.kt
@@ -0,0 +1,33 @@
+package com.betriebsratkanzlei.legalconsenthub.application_form_version.pdf
+
+import org.springframework.boot.context.properties.ConfigurationProperties
+import org.springframework.boot.context.properties.EnableConfigurationProperties
+import org.springframework.boot.context.properties.NestedConfigurationProperty
+import org.springframework.context.annotation.Configuration
+
+@Configuration
+@EnableConfigurationProperties(PdfStorageProperties::class)
+class PdfStorageConfiguration
+
+@ConfigurationProperties(prefix = "legalconsenthub.pdf.storage")
+data class PdfStorageProperties(
+    @NestedConfigurationProperty
+    val filesystem: FileSystemProperties = FileSystemProperties(),
+) {
+    data class FileSystemProperties(
+        /**
+         * Base directory for stored PDFs. In development this defaults to a folder next to the backend code.
+         *
+         * Configure either via application.yaml:
+         * legalconsenthub:
+         *   pdf:
+         *     storage:
+         *       filesystem:
+         *         base-dir: /var/lib/legalconsenthub/pdfs
+         *
+         * or via environment variable:
+         * LEGALCONSENTHUB_PDF_STORAGE_FILESYSTEM_BASE_DIR=/var/lib/legalconsenthub/pdfs
+         */
+        val baseDir: String = ".pdf-store",
+    )
+}
--- a/legalconsenthub/app/components/VersionHistory.vue
+++ b/legalconsenthub/app/components/VersionHistory.vue
@@ -24,6 +24,15 @@
            <UBadge :color="getStatusColor(version.status)">
              {{ getStatusLabel(version.status) }}
            </UBadge>
+            <UButton
+              icon="i-lucide-file-text"
+              size="sm"
+              color="neutral"
+              variant="outline"
+              :label="$t('versions.openPdf')"
+              :to="`/api/application-forms/${applicationFormId}/versions/${version.versionNumber}/pdf`"
+              target="_blank"
+            />
            <UButton
              icon="i-lucide-git-compare"
              size="sm"
--- a/legalconsenthub/app/composables/useApplicationFormNavigation.ts
+++ b/legalconsenthub/app/composables/useApplicationFormNavigation.ts
@@ -1,30 +1,46 @@
 import type { ApplicationFormDto } from '~~/.api-client'

 export async function useApplicationFormNavigation(applicationFormId: string) {
+  const { t } = useI18n()
  const { getApplicationFormById } = useApplicationForm()
+  const { getVersions } = useApplicationFormVersion()

-  const { data, error, refresh } = await useAsyncData<ApplicationFormDto>(
+  const applicationFormAsync = useAsyncData<ApplicationFormDto>(
    `application-form-${applicationFormId}`,
    async () => await getApplicationFormById(applicationFormId),
    { deep: true }
  )

-  if (error.value) {
-    throw createError({ statusText: error.value.message })
+  const versionsAsync = useAsyncData(
+    `application-form-${applicationFormId}-versions-nav`,
+    async () => await getVersions(applicationFormId),
+    { deep: false }
+  )
+
+  await Promise.all([applicationFormAsync, versionsAsync])
+
+  if (applicationFormAsync.error.value) {
+    throw createError({ statusText: applicationFormAsync.error.value.message })
  }

-  const applicationForm = computed<ApplicationFormDto>(() => data?.value as ApplicationFormDto)
+  const applicationForm = computed<ApplicationFormDto>(() => applicationFormAsync.data.value as ApplicationFormDto)
+
+  const latestVersionNumber = computed<number | null>(() => {
+    const versions = versionsAsync.data.value ?? []
+    if (versions.length === 0) return null
+    return Math.max(...versions.map((v) => v.versionNumber ?? 0))
+  })

  const navigationLinks = computed(() => [
    [
      {
-        label: 'Formular',
+        label: t('applicationForms.tabs.form'),
        icon: 'i-lucide-file',
        to: `/application-forms/${applicationForm.value.id}/0`,
        exact: true
      },
      {
-        label: 'Versionen',
+        label: t('applicationForms.tabs.versions'),
        icon: 'i-lucide-file-clock',
        to: `/application-forms/${applicationForm.value.id}/versions`,
        exact: true
@@ -32,16 +48,23 @@ export async function useApplicationFormNavigation(applicationFormId: string) {
    ],
    [
      {
-        label: 'Vorschau',
+        label: t('applicationForms.tabs.preview'),
        icon: 'i-lucide-file-text',
-        to: `/api/application-forms/${applicationForm.value.id}/pdf`,
-        target: '_blank'
+        to: `/api/application-forms/${applicationForm.value.id}/versions/${latestVersionNumber.value}/pdf`,
+        target: '_blank',
+        disabled: Boolean(versionsAsync.error.value) || latestVersionNumber.value === null
      }
    ]
  ])

  function updateApplicationForm(updatedForm: ApplicationFormDto) {
-    data.value = updatedForm
+    applicationFormAsync.data.value = updatedForm
+    // Refresh the versions list so the Preview link points to the latest version.
+    void versionsAsync.refresh()
+  }
+
+  async function refresh() {
+    await Promise.all([applicationFormAsync.refresh(), versionsAsync.refresh()])
  }

  return {
@@ -49,6 +72,6 @@ export async function useApplicationFormNavigation(applicationFormId: string) {
    navigationLinks,
    refresh,
    updateApplicationForm,
-    error
+    error: applicationFormAsync.error
  }
 }
--- a/legalconsenthub/i18n/locales/de.json
+++ b/legalconsenthub/i18n/locales/de.json
@@ -37,6 +37,11 @@
      "next": "Weiter",
      "save": "Speichern",
      "submit": "Einreichen"
+    },
+    "tabs": {
+      "form": "Formular",
+      "versions": "Versionen",
+      "preview": "Vorschau"
    }
  },
  "templates": {
@@ -64,6 +69,7 @@
    "unknownError": "Unbekannter Fehler",
    "compare": "Vergleichen",
    "restore": "Wiederherstellen",
+    "openPdf": "PDF öffnen",
    "restored": "Erfolg",
    "restoredDescription": "Das Formular wurde auf die ausgewählte Version zurückgesetzt.",
    "restoreError": "Version konnte nicht wiederhergestellt werden",
--- a/legalconsenthub/i18n/locales/en.json
+++ b/legalconsenthub/i18n/locales/en.json
@@ -37,6 +37,11 @@
      "next": "Next",
      "save": "Save",
      "submit": "Submit"
+    },
+    "tabs": {
+      "form": "Form",
+      "versions": "Versions",
+      "preview": "Preview"
    }
  },
  "templates": {
@@ -64,6 +69,7 @@
    "unknownError": "Unknown error",
    "compare": "Compare",
    "restore": "Restore",
+    "openPdf": "Open PDF",
    "restored": "Success",
    "restoredDescription": "The form has been restored to the selected version.",
    "restoreError": "Version could not be restored",