feat: implement article version content storage and reconstruction logic; enhance article repository with version management

server/internal/tenant/repository/article_version_storage.go

@@ -0,0 +1,163 @@
+package repository
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/sergi/go-diff/diffmatchpatch"
+
+	"github.com/geo-platform/tenant-api/internal/tenant/repository/generated"
+)
+
+type ArticleVersionContent struct {
+	HTMLContent     *string
+	MarkdownContent *string
+}
+
+type storedArticleVersionContent struct {
+	VersionNo       int
+	HTMLContent     *string
+	MarkdownContent *string
+}
+
+func LoadArticleVersionContent(
+	ctx context.Context,
+	db generated.DBTX,
+	articleID int64,
+	versionID int64,
+) (*ArticleVersionContent, error) {
+	rows, err := db.Query(ctx, `
+		SELECT version_no, html_content, markdown_content
+		FROM article_versions
+		WHERE article_id = $1
+		  AND version_no <= (
+		      SELECT version_no
+		      FROM article_versions
+		      WHERE id = $2 AND article_id = $1
+		  )
+		ORDER BY version_no ASC
+	`, articleID, versionID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	versions, err := collectStoredArticleVersionContents(rows)
+	if err != nil {
+		return nil, err
+	}
+	if len(versions) == 0 {
+		return nil, pgx.ErrNoRows
+	}
+
+	return reconstructStoredArticleVersionContents(versions)
+}
+
+func loadLatestArticleVersionContent(
+	ctx context.Context,
+	db generated.DBTX,
+	articleID int64,
+) (*ArticleVersionContent, error) {
+	rows, err := db.Query(ctx, `
+		SELECT version_no, html_content, markdown_content
+		FROM article_versions
+		WHERE article_id = $1
+		ORDER BY version_no ASC
+	`, articleID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	versions, err := collectStoredArticleVersionContents(rows)
+	if err != nil {
+		return nil, err
+	}
+	if len(versions) == 0 {
+		return &ArticleVersionContent{}, nil
+	}
+
+	return reconstructStoredArticleVersionContents(versions)
+}
+
+func collectStoredArticleVersionContents(rows pgx.Rows) ([]storedArticleVersionContent, error) {
+	versions := make([]storedArticleVersionContent, 0)
+	for rows.Next() {
+		var version storedArticleVersionContent
+		if err := rows.Scan(&version.VersionNo, &version.HTMLContent, &version.MarkdownContent); err != nil {
+			return nil, err
+		}
+		versions = append(versions, version)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return versions, nil
+}
+
+func buildArticleVersionDiffStorage(previous, current ArticleVersionContent) (*string, *string) {
+	return stringPtr(articleVersionPatchText(textValue(previous.HTMLContent), textValue(current.HTMLContent))),
+		stringPtr(articleVersionPatchText(textValue(previous.MarkdownContent), textValue(current.MarkdownContent)))
+}
+
+func reconstructStoredArticleVersionContents(versions []storedArticleVersionContent) (*ArticleVersionContent, error) {
+	var html string
+	var markdown string
+
+	for _, version := range versions {
+		nextHTML, err := applyArticleVersionPatch(html, version.HTMLContent)
+		if err != nil {
+			return nil, fmt.Errorf("apply html patch for version %d: %w", version.VersionNo, err)
+		}
+		nextMarkdown, err := applyArticleVersionPatch(markdown, version.MarkdownContent)
+		if err != nil {
+			return nil, fmt.Errorf("apply markdown patch for version %d: %w", version.VersionNo, err)
+		}
+		html = nextHTML
+		markdown = nextMarkdown
+	}
+
+	result := &ArticleVersionContent{}
+	result.HTMLContent = stringPtr(html)
+	result.MarkdownContent = stringPtr(markdown)
+	return result, nil
+}
+
+func articleVersionPatchText(previous, current string) string {
+	dmp := diffmatchpatch.New()
+	patches := dmp.PatchMake(previous, current)
+	return dmp.PatchToText(patches)
+}
+
+func applyArticleVersionPatch(base string, patchText *string) (string, error) {
+	if patchText == nil || *patchText == "" {
+		return base, nil
+	}
+
+	dmp := diffmatchpatch.New()
+	patches, err := dmp.PatchFromText(*patchText)
+	if err != nil {
+		return "", err
+	}
+
+	next, applied := dmp.PatchApply(patches, base)
+	for _, ok := range applied {
+		if !ok {
+			return "", fmt.Errorf("patch apply failed")
+		}
+	}
+	return next, nil
+}
+
+func textValue(value *string) string {
+	if value == nil {
+		return ""
+	}
+	return *value
+}
+
+func stringPtr(value string) *string {
+	copied := value
+	return &copied
+}