package docs

import (
	"slices"
	"strings"
)

// graph checks cross-record rules: unique IDs and supersession.
func (c *checker) graph(recs []*record) {
	byStem := map[string][]*record{}
	byPath := map[string]*record{}
	for _, r := range recs {
		byStem[r.stem] = append(byStem[r.stem], r)
		byPath["/"+r.path] = r
	}
	for _, group := range byStem {
		for _, r := range group {
			for _, o := range group {
				if o != r {
					c.add(r.path, 1, "duplicate ID %s, also used by %s", r.stem, o.path)
				}
			}
		}
	}
	adrs := recs[:0:0]
	for _, r := range recs {
		if r.kind == "adr" && r.fm != nil {
			adrs = append(adrs, r)
		}
	}
	for _, r := range adrs {
		if len(r.lists["supersedes"]) > 0 && !slices.Contains([]string{"accepted", "superseded", "deprecated"}, r.status) {
			c.add(r.path, r.fm.line("supersedes"), "a record that supersedes another must be accepted, superseded or deprecated, not %s", r.status)
		}
		for _, e := range [][2]string{{"supersedes", "superseded_by"}, {"superseded_by", "supersedes"}} {
			for _, it := range r.lists[e[0]] {
				if o := byPath[it.v]; o != nil && o.kind == "adr" && !slices.ContainsFunc(o.lists[e[1]], func(x item) bool { return x.v == "/"+r.path }) {
					c.add(r.path, it.line, "%s lists %s, which must list this record in %s", e[0], it.v, e[1])
				}
			}
		}
	}
	// Cycles over supersedes edges: report once, on the first record (in path order) that closes one.
	const (
		visiting = 1
		done     = 2
	)
	state := map[*record]int{}
	var visit func(r *record)
	visit = func(r *record) {
		state[r] = visiting
		for _, it := range r.lists["supersedes"] {
			o := byPath[it.v]
			if o == nil || o.kind != "adr" {
				continue
			}
			switch state[o] {
			case visiting:
				c.add(r.path, it.line, "supersession cycle through %s", strings.TrimPrefix(it.v, "/"))
			case 0:
				visit(o)
			}
		}
		state[r] = done
	}
	for _, r := range adrs {
		if state[r] == 0 {
			visit(r)
		}
	}
}