package check

import (
	"path"
	"regexp"
	"strings"

	"git.vakhrushev.me/av/convy/internal/doc"
	"git.vakhrushev.me/av/convy/internal/lang"
	"git.vakhrushev.me/av/convy/internal/suite"
)

// checkSpread checks what bears on a document travelling to a consumer. It
// applies to convention files only: the document the suite governs itself by
// travels nowhere, and a canon path inside it is lawful.
func checkSpread(s *suite.Suite, d *doc.Document, rep *Report) {
	checkTopic(s, d, rep)
	checkAxis(d, rep)
	checkExtends(s, d, rep)
	checkMechanized(s, d, rep)
	checkCanonPaths(s, d, rep)
	checkForeignTopicPrefix(s, d, rep)
}

// checkTopic reconciles the topic from the front matter with the manifest
// (META-28, META-29).
func checkTopic(s *suite.Suite, d *doc.Document, rep *Report) {
	topic := d.Front.Topic
	at := d.Front.At["topic"]
	switch {
	case s.Manifest.TopicRetired(topic):
		rep.Errorf(Spread, d.Path, at,
			"topic %q is listed among the retired ones: a retired name is never handed to another topic", topic)
	case !s.Manifest.TopicLive(topic):
		rep.Errorf(Spread, d.Path, at,
			"topic %q is not declared in the suite manifest", topic)
	}
}

// checkAxis reconciles the declared axis with the path of the file. An axis is
// declared in the front matter rather than derived from the path (META-38); but
// once axis directories are in use, a divergence means the file moved and the
// front matter did not.
func checkAxis(d *doc.Document, rep *Report) {
	parts := strings.Split(path.Dir(d.Path), "/")
	for i := 0; i+1 < len(parts); i++ {
		var declared, key string
		switch parts[i] {
		case "lang":
			declared, key = d.Front.Lang, "lang"
		case "stack":
			declared, key = d.Front.Stack, "stack"
		default:
			continue
		}
		if declared == parts[i+1] {
			continue
		}
		at := d.Front.At[key]
		if at == 0 {
			at = d.Front.At["prefix"]
		}
		rep.Errorf(Spread, d.Path, at,
			"the path puts the file on axis %s=%s, while the front matter declares %s=%q", key, parts[i+1], key, declared)
	}
}

// checkExtends verifies that the declared base exists and belongs to the same
// topic. The key documents the tie between layers for a human — and
// documentation that lies is worse than none.
func checkExtends(s *suite.Suite, d *doc.Document, rep *Report) {
	if d.Front.Extends == "" {
		return
	}
	at := d.Front.At["extends"]
	target := resolveExtends(s, d.Front.Extends)
	if target == nil {
		rep.Errorf(Spread, d.Path, at,
			"extends points at %q, and the suite holds no such file", d.Front.Extends)
		return
	}
	if target.Front.Topic != d.Front.Topic {
		rep.Errorf(Spread, d.Path, at,
			"extends points at %q with topic %q, while the file carries topic %q: the layers of one topic declare one name",
			d.Front.Extends, target.Front.Topic, d.Front.Topic)
	}
	if target.Front.Axis() {
		rep.Errorf(Spread, d.Path, at,
			"extends points at %q, which is not a base layer: it declares an axis", d.Front.Extends)
	}
}

// resolveExtends looks up the document at the path written in extends. The path
// is given from the conventions directory, so both it and a path from the root
// of the suite are tried.
func resolveExtends(s *suite.Suite, ref string) *doc.Document {
	ref = path.Clean(strings.TrimPrefix(ref, "./"))
	for _, d := range s.Docs {
		if d.Path == ref || strings.HasSuffix(d.Path, "/"+ref) {
			return d
		}
	}
	return nil
}

// checkMechanized looks for the mark of mechanization in the text of a
// convention. Whether a norm is mechanized is a property of a repository rather
// than of the suite, so the place of the mark is the local part of the copy
// (META-7).
func checkMechanized(s *suite.Suite, d *doc.Document, rep *Report) {
	word := s.Vocab.MarkWord(lang.Mechanized)
	if word == "" {
		return
	}
	version, hasVersion := versionParagraph(s, d)
	d.Prose(func(n int, text string) bool {
		if hasVersion && n >= version.Start && n <= version.End {
			return true
		}
		if containsWord(text, word) {
			rep.Errorf(Spread, d.Path, n,
				"the %s mark stands in the text of a convention: its place is the note of mechanization in the local part of the copy", word)
		}
		return true
	})
}

// mdPathRe catches what looks like a path to a file of the suite.
var mdPathRe = regexp.MustCompile(`[\w./-]+\.md`)

// checkCanonPaths looks for the path of a canon file in the text of a
// convention (META-21). In a consumer's repository a convention lies assembled,
// the layers of one topic are sections of one file, and the path
// `lang/go/logging.md` does not exist there: a reference to it dies on assembly,
// and dies in silence — the text stays coherent.
//
// Inline code is not cut out here: a path in backticks is still a path.
func checkCanonPaths(s *suite.Suite, d *doc.Document, rep *Report) {
	for n := d.Body; n <= d.Len(); n++ {
		if d.Fenced(n) {
			continue
		}
		for _, candidate := range mdPathRe.FindAllString(d.Line(n), -1) {
			target := resolveExtends(s, candidate)
			if target == nil && !s.Exists(candidate) {
				continue
			}
			rep.Errorf(Spread, d.Path, n,
				"the text holds the canon file path %q: refer by the name of a topic or the identifier of a rule", candidate)
		}
	}
}

// checkForeignTopicPrefix looks for the prefix of a foreign topic inside a norm
// block (META-20). The norm of a rule must be executable holding this one file:
// a repository subscribes to an arbitrary subset of the conventions, and it has
// no dependency graph by construction. The prefix of the base layer of its own
// topic is allowed there (META-24) — an assembled file starts with that layer
// whatever language and stack were chosen.
func checkForeignTopicPrefix(s *suite.Suite, d *doc.Document, rep *Report) {
	own := s.Prefix(d)
	for _, r := range d.Rules {
		for _, norm := range r.Norms() {
			for _, ref := range refsIn(d, norm.Start, norm.End) {
				if ref.Prefix == own || strings.HasPrefix(ref.Prefix, "X") {
					continue
				}
				target, ok := s.ByPrefix[ref.Prefix]
				if !ok {
					continue
				}
				if target.Front.Topic != d.Front.Topic {
					rep.Errorf(Spread, d.Path, ref.Line,
						"the norm of %s refers to %s from the foreign topic %q: only the rationale looks outward",
						r.ID(), ref.Text, target.Front.Topic)
					continue
				}
				if target.Front.Axis() {
					rep.Errorf(Spread, d.Path, ref.Line,
						"the norm of %s refers to %s, a layer of its own topic but not the base one: that layer reaches the copy through the manifest, so there is no guarantee it stands nearby",
						r.ID(), ref.Text)
				}
			}
		}
	}
}