package docsite

import (
	"fmt"
	"slices"
	"strings"

	gast "github.com/yuin/goldmark/ast"
)

// calloutTypes are the only `> [!TYPE]` callouts the theme renders.
var calloutTypes = []string{"NOTE", "TIP", "WARNING"}

// checkPolicy enforces the page content rules:
//   - every Go-lexer fence in a docs/ page carries src=, at any depth
//     (module READMEs are rendered as written, D-18);
//   - callouts are NOTE, TIP or WARNING;
//   - docs/ headings are plain ASCII text without links or code spans.
func (s *site) checkPolicy(docs []parsedDoc) ([]Problem, error) {
	var problems []Problem
	for _, d := range docs {
		if d.page == nil {
			continue
		}
		guide := d.page.Module == ""
		if guide {
			fences, err := collectFences(d.doc, d.body)
			if err != nil {
				return nil, err
			}
			for _, f := range fences {
				if _, hasSrc := ParseSrc(f.info); goLang(f.lang) && !hasSrc {
					problems = append(problems, Problem{File: d.file, Line: d.line + f.line, Rule: "snippet",
						Message: f.lang + " code block has no src= reference"})
				}
			}
		}
		problems = append(problems, calloutProblems(d)...)
		if guide {
			problems = append(problems, headingProblems(d)...)
		}
	}
	return problems, nil
}

// calloutProblems reports blockquotes whose marker is not NOTE, TIP or
// WARNING. calloutTransformer has already turned the known types into
// callout nodes, so a remaining blockquote with a marker is unknown.
// The marker is read from the AST, so a copy of it inside a code fence
// is not a callout.
func calloutProblems(d parsedDoc) []Problem {
	var problems []Problem
	_ = gast.Walk(d.doc, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
		bq, ok := n.(*gast.Blockquote)
		if !entering || !ok {
			return gast.WalkContinue, nil
		}
		para, ok := bq.FirstChild().(*gast.Paragraph)
		if !ok || para.Lines().Len() == 0 {
			return gast.WalkContinue, nil
		}
		first := para.Lines().At(0)
		m := calloutLine.FindStringSubmatch(strings.TrimSpace(string(first.Value(d.body))))
		if m == nil || slices.Contains(calloutTypes, m[1]) {
			return gast.WalkContinue, nil
		}
		problems = append(problems, Problem{File: d.file, Line: lineOf(d.body, first.Start, d.line), Rule: "callout",
			Message: fmt.Sprintf("unknown type %s (use NOTE, TIP or WARNING)", m[1])})
		return gast.WalkContinue, nil
	})
	return problems
}

const headingMessage = "headings must be plain ASCII text without links or code"

// headingProblems reports headings with a link, image, code span or raw
// HTML, or with non-ASCII text: their IDs would not be stable across the
// site, Gitea and GitHub.
func headingProblems(d parsedDoc) []Problem {
	var problems []Problem
	_ = gast.Walk(d.doc, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
		h, ok := n.(*gast.Heading)
		if !entering || !ok {
			return gast.WalkContinue, nil
		}
		bad := false
		_ = gast.Walk(h, func(c gast.Node, entering bool) (gast.WalkStatus, error) {
			if !entering {
				return gast.WalkContinue, nil
			}
			switch t := c.(type) {
			case *gast.Link, *gast.Image, *gast.CodeSpan, *gast.RawHTML, *gast.AutoLink:
				bad = true
				return gast.WalkStop, nil
			case *gast.Text:
				for _, b := range t.Segment.Value(d.body) {
					if b >= 0x80 {
						bad = true
						return gast.WalkStop, nil
					}
				}
			}
			return gast.WalkContinue, nil
		})
		if bad {
			off := -1
			if h.Lines().Len() > 0 {
				off = h.Lines().At(0).Start
			}
			problems = append(problems, Problem{File: d.file, Line: lineOf(d.body, off, d.line), Rule: "heading", Message: headingMessage})
		}
		return gast.WalkSkipChildren, nil
	})
	return problems
}