# Paging Feature Design

## Overview

Introduce offset-based pagination to the admin post list and the generated static site (both post listings and category listings).

## Data Layer

### New `sites` column

Add `posts_per_page INTEGER NOT NULL DEFAULT 10` to the `sites` table. This setting controls the number of posts per page on the **generated static site only**.

### New SQL queries

- `CountPostsOfSite(siteID, showDeleted)` — returns total post count for the site
- `CountPostsOfCategory(categoryID)` — returns total published post count for a category

### Model changes

**`models.Site`** — add field:
```go
PostsPerPage int
```

**New shared type** (`models/paging.go`):
```go
type PageInfo struct {
    CurrentPage  int
    TotalPages   int
    PostsPerPage int
}
```

Existing `db.PagingParams` and queries (`SelectPostsOfSite`, `SelectPostsOfCategory`) already support `LIMIT/OFFSET` and remain unchanged.

## Admin Section

### Post list pagination

- **Page size: hardcoded at 25** (not tied to the `PostsPerPage` site setting)
- Handler (`handlers/posts.go` `Index()`) reads a `page` query parameter (default 1)
- Computes offset as `(page - 1) * 25`
- Fetches total post count via new `CountPosts()` service method to build `PageInfo`
- Passes `PageInfo` to template

### Service changes

- `ListPosts()` accepts paging params from the handler instead of hardcoding them
- New `CountPosts()` method that calls the count query

### Template (`views/posts/index.html`)

- Full numbered pagination with Previous/Next below the post list: `< 1 2 3 ... 10 >`
- Preserves existing query params (e.g. `?filter=deleted`) when paginating
- Both regular post list and trash view are paginated

### Site settings form

- Add "Posts per page" number input to `views/sitesettings/general.html`
- Add `PostsPerPage` field to `UpdateSiteSettingsParams`
- Server-side validation: minimum 1, maximum 100

## Generated Static Site

### URL structure

Post listing pages:
- `/posts/` — page 1
- `/posts/page/2/` — page 2
- `/posts/page/N/` — page N

Category listing pages:
- `/categories/<slug>/` — page 1
- `/categories/<slug>/page/2/` — page 2
- `/categories/<slug>/page/N/` — page N

### Site root

`/` (site root) shows the same content as `/posts/` (page 1 of all posts).

### Builder changes (`providers/sitebuilder/builder.go`)

- Instead of rendering one `posts_list.html` with all posts, generate multiple page files
- Uses `site.PostsPerPage` from the site setting to determine page size
- Same pattern for category pages

### Publisher changes (`services/publisher/iter.go`)

- Existing iterator fetches posts in batches of 50 internally — this stays as-is
- The builder chunks posts into pages of `PostsPerPage` size and renders each page as a separate HTML file

### Template (`layouts/simplecss/templates/posts_list.html`)

- Receives `PageInfo` plus the posts for that page
- Renders **Previous / Next** links only (no numbered pagination)
- Previous link hidden on page 1; Next link hidden on last page

## Approach

Offset-based pagination using the existing `db.PagingParams` infrastructure. Page number maps to offset: `offset = (page - 1) * postsPerPage`.