package layer

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// Form is one of the two shapes §11 accepts for a declaration: a layer: key in
// INTENT.md frontmatter, or an equivalent declaration file.
type Form struct {
	Source string // path relative to the survey root, "" when the form is absent
	Layer  string // the layer: value exactly as written
	Role   string
	Found  bool
	// InVocabulary reports whether Layer is in the §3 vocabulary as written.
	// Deliberately case-sensitive: whether §3 is case-insensitive is the open
	// question (FLEX-WP-0030 B1), and folding case here would hide it.
	InVocabulary bool
}

// SurveyRow is one repository's declaration as observed from outside. It holds
// BOTH forms, because §11 permits either and does not say which is
// authoritative when a repository carries both and they disagree.
type SurveyRow struct {
	Repo   string
	Intent Form // INTENT.md frontmatter
	File   Form // layer.yaml or equivalent
}

// Declared reports whether any machine-readable form was found.
func (r SurveyRow) Declared() bool { return r.Intent.Found || r.File.Found }

// SelfDisagrees reports a repository whose two §11 forms state different layer
// values. Case counts: that is the point of the finding, not an artifact of it.
func (r SurveyRow) SelfDisagrees() bool {
	return r.Intent.Found && r.File.Found && r.Intent.Layer != r.File.Layer
}

// Layer returns the value to report, preferring INTENT.md, which §11 names
// first. The preference is this survey's, not a ruling — which form governs is
// exactly what FLEX-WP-0030 B1 asks.
func (r SurveyRow) Layer() string {
	if r.Intent.Found {
		return r.Intent.Layer
	}
	return r.File.Layer
}

var declarationFiles = []string{"layer.yaml", "layer.yml"}

// SurveyDeclarations reads both §11 forms for every repository under root.
//
// It checks ONE property: whether each layer: value sits in the §3 vocabulary
// as written. It deliberately does not apply flex-auth's own declaration rules
// — pep_stance, tooling_contacts, conformance_record — to any other repository.
// Those are flex-auth's invariants for flex-auth, and §11 is explicit that a
// layer stated about a repository by another repository is not a declaration.
// A survey that graded peers by the surveyor's house rules would be that defect
// wearing a tool for a hat.
func SurveyDeclarations(root string, repos []string) ([]SurveyRow, error) {
	var rows []SurveyRow
	for _, repo := range repos {
		row := SurveyRow{Repo: repo}
		row.Intent = readForm(root, filepath.Join(repo, "INTENT.md"))
		for _, name := range declarationFiles {
			if f := readForm(root, filepath.Join(repo, name)); f.Found {
				row.File = f
				break
			}
		}
		rows = append(rows, row)
	}
	sort.Slice(rows, func(i, j int) bool { return rows[i].Repo < rows[j].Repo })
	return rows, nil
}

func readForm(root, rel string) Form {
	path := filepath.Join(root, rel)
	if _, err := os.Stat(path); err != nil {
		return Form{}
	}
	decl, err := loadAnyDeclaration(path)
	if err != nil || strings.TrimSpace(decl.Layer) == "" {
		return Form{}
	}
	return Form{
		Source:       rel,
		Layer:        decl.Layer,
		Role:         decl.Role,
		Found:        true,
		InVocabulary: validLayers[decl.Layer],
	}
}

// loadAnyDeclaration reads INTENT.md frontmatter or a bare declaration file.
func loadAnyDeclaration(path string) (Declaration, error) {
	if strings.HasSuffix(path, ".md") {
		return LoadDeclaration(path)
	}
	body, err := os.ReadFile(path)
	if err != nil {
		return Declaration{}, err
	}
	return parseDeclarationYAML(string(body))
}

// Spellings groups every observed layer: value across both forms, so the spread
// is a result rather than a claim.
func Spellings(rows []SurveyRow) map[string][]string {
	out := map[string][]string{}
	add := func(v, where string) {
		if v != "" {
			out[v] = append(out[v], where)
		}
	}
	for _, r := range rows {
		if r.Intent.Found {
			add(r.Intent.Layer, r.Repo+"/INTENT.md")
		}
		if r.File.Found {
			add(r.File.Layer, r.File.Source)
		}
	}
	return out
}

// Undeclared lists repositories with no machine-readable declaration in either form.
func Undeclared(rows []SurveyRow) []string {
	var out []string
	for _, r := range rows {
		if !r.Declared() {
			out = append(out, r.Repo)
		}
	}
	return out
}

// SelfDisagreeing lists repositories whose two §11 forms disagree.
func SelfDisagreeing(rows []SurveyRow) []SurveyRow {
	var out []SurveyRow
	for _, r := range rows {
		if r.SelfDisagrees() {
			out = append(out, r)
		}
	}
	return out
}

// FormatSurvey renders the survey as a stable, diffable report.
func FormatSurvey(rows []SurveyRow) string {
	var b strings.Builder
	fmt.Fprintf(&b, "%-18s %-16s %-16s %s\n", "REPO", "INTENT.md", "DECL FILE", "NOTE")
	for _, r := range rows {
		note := ""
		switch {
		case !r.Declared():
			note = "NO DECLARATION (§11)"
		case r.SelfDisagrees():
			note = "forms disagree"
		case !r.Intent.Found:
			note = "declaration file only"
		case !r.File.Found:
			note = "INTENT.md only"
		}
		for _, f := range []Form{r.Intent, r.File} {
			if f.Found && !f.InVocabulary {
				note += "; outside §3 vocabulary as written"
			}
		}
		fmt.Fprintf(&b, "%-18s %-16s %-16s %s\n", r.Repo, dash(r.Intent.Layer), dash(r.File.Layer), note)
	}
	return b.String()
}

func dash(s string) string {
	if strings.TrimSpace(s) == "" {
		return "—"
	}
	return s
}