package web

import (
	"strings"

	"github.com/gramanas/blogspace/internal/store"
)

// Listings can show a summary of each post instead of the whole thing
// (theme.list_style). The blogger marks where the summary ends with
// <!--more--> in the source; without the marker a Markdown post is cut after
// its first summaryWords words, at a block boundary, and an HTML post is shown
// whole (cutting hand-written markup blind would leave tags open).

const (
	moreMarker   = "<!--more-->"
	summaryWords = 70
)

// fillExcerpts sets what the list shows of each post: the summary when the
// theme asks for one, the whole body otherwise.
func fillExcerpts(theme Theme, posts []store.Post) {
	for i := range posts {
		p := &posts[i]
		p.Excerpt, p.HasMore = p.BodyHTML, false
		if theme.ListStyle == "summary" {
			p.Excerpt, p.HasMore = postSummary(p)
		}
	}
}

// postSummary renders the part of the post a listing shows, and says whether
// there is more to read.
func postSummary(p *store.Post) (string, bool) {
	if before, _, ok := strings.Cut(p.BodyMD, moreMarker); ok {
		return renderBody(p.Format, before), true
	}
	if p.Format == store.FormatHTML {
		return p.BodyHTML, false
	}
	head, cut := leadingBlocks(p.BodyMD, summaryWords)
	if !cut {
		return p.BodyHTML, false
	}
	return renderBody(p.Format, head), true
}

// leadingBlocks returns the blank-line separated blocks from the start of the
// Markdown up to the first that brings the word count to n, and whether
// anything was left out. A fenced code block is never cut in two.
func leadingBlocks(md string, n int) (string, bool) {
	blocks := strings.Split(md, "\n\n")
	words, fences := 0, 0
	for i, b := range blocks {
		words += len(strings.Fields(b))
		fences += strings.Count(b, "```")
		if words >= n && fences%2 == 0 {
			return strings.Join(blocks[:i+1], "\n\n"), i+1 < len(blocks)
		}
	}
	return md, false
}