package check

import (
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"git.vakhrushev.me/av/convy/internal/manifest"
	"git.vakhrushev.me/av/convy/internal/source"
	"git.vakhrushev.me/av/convy/internal/suite"
)

// Suite runs every check of a suite and returns the report.
func Suite(s *suite.Suite) *Report {
	rep := &Report{}
	checkManifest(s, rep)
	checkLanguageSource(s, rep)
	checkTopicNames(s, rep)
	checkBaseLayers(s, rep)
	checkSelfGoverning(s, rep)
	checkReadingVocabulary(s, rep)

	for _, d := range s.Docs {
		checkForm(s, d, rep)
		checkLinks(s, d, rep)
		if d.Front.Topic != "" {
			checkSpread(s, d, rep)
		}
	}
	return rep
}

// checkManifest checks the manifest itself: the shape of prefixes, live and
// retired not overlapping, the declared files being present and no undeclared
// ones lying around.
func checkManifest(s *suite.Suite, rep *Report) {
	m := s.Manifest

	for _, key := range m.Undecoded {
		rep.Warnf(Manifest, manifest.Name, 0, "the key %s is unknown to the tool", key)
	}
	// The documents about the language are named relative to the level they
	// belong to. While that level is the suite, the files have to be here; once
	// the language lives apart, they are out of reach of a check that runs on
	// every edit and must not touch the network.
	if m.Language.Source == "" {
		for _, name := range []string{m.Language.Description, m.Language.Reading} {
			if name != "" && !s.Exists(name) {
				rep.Errorf(Manifest, manifest.Name, 0, "the [language] section declares the document %q, and the file is missing", name)
			}
		}
	}

	byPath := make(map[string][]string)
	for _, prefix := range m.LivePrefixes() {
		if err := manifest.ValidPrefix(prefix); err != nil {
			rep.Errorf(Manifest, manifest.Name, 0, "%s", err)
		}
		if m.PrefixRetired(prefix) {
			rep.Errorf(Manifest, manifest.Name, 0,
				"prefix %s is listed both live and retired: a retired one is never reissued", prefix)
		}
		path := m.Prefixes.Live[prefix]
		byPath[path] = append(byPath[path], prefix)
	}
	for _, path := range sortedKeys(byPath) {
		if prefixes := byPath[path]; len(prefixes) > 1 {
			sort.Strings(prefixes)
			rep.Errorf(Manifest, manifest.Name, 0,
				"the file %q has several prefixes declared for it (%v): a prefix belongs to one file", path, prefixes)
		}
	}
	for prefix := range m.Prefixes.Retired {
		if err := manifest.ValidPrefix(prefix); err != nil {
			rep.Errorf(Manifest, manifest.Name, 0, "among the retired ones: %s", err)
		}
	}

	for _, prefix := range sortedKeys(s.Missing) {
		rep.Errorf(Manifest, manifest.Name, 0,
			"prefix %s is assigned to the file %q, which the suite does not hold", prefix, s.Missing[prefix])
	}
	for _, path := range s.Unregistered {
		rep.Errorf(Manifest, path, 1,
			"the file is written in the conventions language yet not declared in the suite manifest: for the suite it does not exist")
	}
	for _, err := range s.Broken {
		rep.Errorf(Manifest, manifest.Name, 0, "%s", err)
	}

	for _, topic := range m.LiveTopics() {
		if m.TopicRetired(topic) {
			rep.Errorf(Manifest, manifest.Name, 0,
				"topic %q is listed both live and retired", topic)
		}
		if len(s.Layers(topic)) == 0 {
			rep.Errorf(Manifest, manifest.Name, 0,
				"topic %q is declared live while the suite holds no layer of it: a topic lives as long as at least one layer does", topic)
		}
	}
}

var (
	// topicNameRe is the hard bound: a topic name reaches the file system of
	// a consumer, so it has to be usable as a file name — Latin letters,
	// digits and the plain separators.
	topicNameRe = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]*$`)
	// kebabRe is the recommended shape, and only a recommendation.
	kebabRe = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)
)

// checkTopicNames checks the shape of topic names. A name lands both in a
// consumer's file system and in their manifest, which is where the hard bound
// comes from; lower kebab-case on top of that is a recommendation and speaks as
// a warning.
func checkTopicNames(s *suite.Suite, rep *Report) {
	for _, topic := range s.Manifest.LiveTopics() {
		switch {
		case !topicNameRe.MatchString(topic):
			rep.Errorf(Manifest, manifest.Name, 0,
				"the topic name %q is not usable as a file name: a name is written in Latin letters and travels into the file system of a consumer", topic)
		case !kebabRe.MatchString(topic):
			rep.Warnf(Manifest, manifest.Name, 0,
				"the topic name %q is not lower kebab-case, which is the recommended shape", topic)
		}
	}
}

// checkSelfGoverning guards the document without a topic.
//
// A topic-less document is the one the suite governs itself by: it travels
// nowhere and cannot be subscribed to, so it gets no spread checks. A
// convention that lost its topic key looks exactly the same, and that loss is
// the expensive one — the file keeps every check of form while quietly dropping
// every check about travelling to a consumer.
//
// Which file it is, the manifest says. Guessing was tried and does not reach:
// "there is one of them" and "it has no axis keys" both hold for a suite whose
// only topic-less file is a convention with the key knocked out.
func checkSelfGoverning(s *suite.Suite, rep *Report) {
	declared := s.Manifest.Governance
	if declared != "" && !s.Exists(declared) {
		rep.Errorf(Manifest, manifest.Name, 0,
			"governance names %q, and the file is missing", declared)
	}

	for _, d := range s.Docs {
		if d.Front.Topic != "" {
			if s.Manifest.Governs(d.Path) {
				rep.Errorf(Manifest, d.Path, d.Front.At["topic"],
					"the manifest names this file the one the suite governs itself by, and it declares topic %q: such a document belongs to no topic, because nobody may subscribe to it", d.Front.Topic)
			}
			continue
		}

		switch {
		case declared == "":
			rep.Errorf(Manifest, d.Path, 1,
				"the file declares no topic, and the manifest names no document the suite governs itself by: either the topic key is lost, or the manifest has to say governance = %q", d.Path)
		case !s.Manifest.Governs(d.Path):
			rep.Errorf(Manifest, d.Path, 1,
				"the file declares no topic, while the manifest names %q as the one the suite governs itself by: a convention without a topic has lost the key", declared)
		case d.Front.Axis() || d.Front.Extends != "":
			rep.Errorf(Manifest, d.Path, d.Front.At["prefix"],
				"the document the suite governs itself by carries the keys of a layer: it is nobody's layer, having no topic to be a layer of")
		}
	}
}

// checkReadingVocabulary checks that the short account of the language names
// every word of the vocabulary (META-30).
//
// The full account stays with the author of the suite, while the rules are
// applied by the reader of a copy — a person or an agent in a foreign
// repository who holds the short one and nothing else. Let the two drift apart
// and that reader starts reading the words by an older version: ДОПУСКАЕТСЯ
// turns back into an everyday "you may", a departure from ДОЛЖЕН stops
// demanding a record. Exactly what the words were introduced for fails, and it
// fails in silence.
func checkReadingVocabulary(s *suite.Suite, rep *Report) {
	name := s.Manifest.Language.Reading
	if s.Manifest.Language.Source != "" {
		// The account lies at a level of its own, and reaching it costs a
		// fetch. Checking the integrity of a suite runs on every edit, so it
		// stays local; the reference itself is checked instead.
		return
	}
	if name == "" {
		// A suite that has not written the document yet; `suite init` says so
		// among the next steps, and repeating it on every run is noise.
		return
	}
	body, err := os.ReadFile(filepath.Join(s.Root, filepath.FromSlash(name)))
	if err != nil {
		// The missing file is reported by the manifest check already.
		return
	}

	var missing []string
	for _, word := range s.Vocab.Words() {
		if !containsWord(string(body), word) {
			missing = append(missing, word)
		}
	}
	if len(missing) > 0 {
		rep.Errorf(Form, name, 0,
			"the short account of the language does not name %s: it is the only key to the text of a rule a reader of a copy holds, and a word missing from it is a word read by whatever version the reader remembers",
			strings.Join(missing, ", "))
	}
}

// checkBaseLayers checks that a topic holds no more than one layer without axis
// keys. The base layer is the only one of its kind: it reaches every copy, and a
// second such layer would mean two base texts in one assembled file.
func checkBaseLayers(s *suite.Suite, rep *Report) {
	for _, topic := range s.Manifest.LiveTopics() {
		var base []string
		for _, d := range s.Layers(topic) {
			if !d.Front.Axis() {
				base = append(base, d.Path)
			}
		}
		if len(base) > 1 {
			sort.Strings(base)
			for _, path := range base[1:] {
				rep.Errorf(Spread, path, 1,
					"topic %q holds more than one layer without axis keys: the base layer is the only one of its kind, and the candidates are %v",
					topic, base)
			}
		}
	}
}

func sortedKeys[V any](m map[string]V) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}

// checkLanguageSource checks the reference to the level of the language. What
// it names cannot be reached without a fetch, and a check of a suite does not
// fetch — but a reference that means nothing is caught here rather than at the
// first assembly in a foreign repository.
func checkLanguageSource(s *suite.Suite, rep *Report) {
	raw := s.Manifest.Language.Source
	if raw == "" {
		return
	}
	if _, err := source.Parse(raw); err != nil {
		rep.Errorf(Manifest, manifest.Name, 0, "[language] source: %s", err)
	}
}