1 files changed, 84 insertions, 0 deletions
diff --git a/internal/post/post.go b/internal/post/post.go
new file mode 100644
index 0000000..cdef546
--- /dev/null
+++ b/internal/post/post.go
@@ -0,0 +1,84 @@
+// Package post defines the Post data model and its JSON serialisation format.
+// Each post is stored as post.json inside its own directory under outdir/posts/.
+// This allows pages to be re-generated without re-processing the original inputs.
+package post
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+// Type enumerates the supported input content types.
+type Type string
+
+const (
+	TypeText     Type = "text"
+	TypeMarkdown Type = "markdown"
+	TypeImage    Type = "image"
+	TypeAudio    Type = "audio"
+)
+
+// Post represents a single microblog entry.
+// It is persisted as post.json in outdir/posts/<ID>/.
+type Post struct {
+	// ID is the unique directory-name-safe timestamp, e.g. "2026-04-09-143022".
+	ID string `json:"id"`
+
+	// Timestamp is the moment the post was processed (UTC).
+	Timestamp time.Time `json:"timestamp"`
+
+	// PostType determines how the content was generated and how it should be rendered.
+	PostType Type `json:"type"`
+
+	// Content is the pre-rendered HTML snippet for this post (without outer post-card wrapper).
+	Content string `json:"content"`
+
+	// Assets lists filenames (not paths) of any asset files stored alongside post.json.
+	Assets []string `json:"assets,omitempty"`
+}
+
+// Save writes the post as post.json into dir.
+func (p *Post) Save(dir string) error {
+	data, err := json.MarshalIndent(p, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal post %s: %w", p.ID, err)
+	}
+
+	path := filepath.Join(dir, "post.json")
+	if err := os.WriteFile(path, data, 0o644); err != nil {
+		return fmt.Errorf("write post.json for %s: %w", p.ID, err)
+	}
+
+	return nil
+}
+
+// Load reads and parses post.json from dir.
+func Load(dir string) (*Post, error) {
+	path := filepath.Join(dir, "post.json")
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read post.json in %s: %w", dir, err)
+	}
+
+	var p Post
+	if err := json.Unmarshal(data, &p); err != nil {
+		return nil, fmt.Errorf("unmarshal post.json in %s: %w", dir, err)
+	}
+
+	return &p, nil
+}
+
+// NewID generates a unique post ID from the given time.
+// Format: YYYY-MM-DD-HHmmss, optionally suffixed with -N for collisions.
+func NewID(t time.Time, suffix int) string {
+	base := t.UTC().Format("2006-01-02-150405")
+	if suffix == 0 {
+		return base
+	}
+
+	return fmt.Sprintf("%s-%d", base, suffix)
+}