// Package issue is what an issue IS. The domain layer.
//
// It knows the canonical markdown format, the label taxonomy, validation, and
// the dependency graph. It knows NOTHING about any tracker: no Gitea, no
// logins, no HTTP, no issue numbers. The layering rule is mechanically checked
// — see TestDomainImportsNothing, which walks this package's transitive
// dependencies and fails on anything outside the standard library and
// internal/project.
//
// Delete the transport entirely and this layer keeps working: issues that live
// only on this machine are first-class, not drafts on their way somewhere.
//
// Identity is a slug derived from the title, and it is the only identity the
// domain has. The file name is the id:
//
//	.tea/issues/wire-sqlc-appclick.md
//
//	---
//	id: wire-sqlc-appclick
//	state: open
//	labels: [type/task, tech/sql]
//	assignees: [naudachu]
//	milestone: v0.2
//	depends: [migrate-schema]
//	origin: gitea
//	gitea: owner/repo#42
//	synced: 2026-08-07T18:40:00Z
//	---
//	# Wire sqlc into the appclick repo layer
//
//	## Summary
//	...
//
// Keys down to origin are owned here. Everything below is written by the sync
// layer; this package carries those keys through load/save verbatim in Extra
// and never reads them. That passthrough is what lets one file represent both
// a local issue and a synced one without the domain learning a second
// vocabulary.
//
// Every metadata field is one line and lists are inline, so plain grep works
// without a parser:
//
//	grep -l 'labels:.*type/bug' .tea/issues/*.md
//	grep -ln 'depends:.*migrate-schema' .tea/issues/*.md   # who depends on it
package issue

import (
	"fmt"
	"regexp"
	"strings"
)

// Origin is "does this issue exist anywhere but here" — a fact about the work,
// so it is owned here. Its value is Local or a tracker's name; what that name
// means, and the handle that goes with it (gitea: owner/repo#42), stay foreign
// keys this layer carries but never reads.
const Local = "local"

// DomainKeys are the metadata fields this layer owns, in render order. Foreign
// keys render after these, sorted, so the sync layer can add fields without
// touching this list.
var DomainKeys = []string{"id", "state", "labels", "assignees", "milestone",
	"depends", "origin"}

var listKeys = map[string]bool{"labels": true, "assignees": true, "depends": true}

// States an issue may be in.
var States = []string{"open", "closed"}

var slugOK = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)

var slugPunct = regexp.MustCompile(`[^a-z0-9]+`)

// Issue is one unit of work. Extra holds metadata this layer does not own.
type Issue struct {
	ID        string
	Title     string
	Body      string
	State     string
	Labels    []string
	Assignees []string
	Milestone string
	Depends   []string
	Origin    string
	Extra     map[string]string
}

// IsLocal reports whether this issue exists nowhere but here.
//
// A complete state, not a pending one — and the state in which this file is
// the only copy of the work. An issue whose Origin names somewhere else can be
// fetched from there again; this one cannot.
func (i *Issue) IsLocal() bool { return i.Origin == Local }

// Type is the value of the mandatory, exclusive type/* label.
func (i *Issue) Type() string { return i.namespaced("type/") }

// Severity is the value of the optional, exclusive severity/* label.
func (i *Issue) Severity() string { return i.namespaced("severity/") }

func (i *Issue) namespaced(prefix string) string {
	for _, l := range i.Labels {
		if v, ok := strings.CutPrefix(l, prefix); ok {
			return v
		}
	}
	return ""
}

// FromText parses a stored issue. A non-empty id overrides the one in the
// metadata block, which is how the store makes the file name authoritative.
func FromText(text, id string) *Issue {
	meta, title, body := ParseMeta(text)

	extra := map[string]string{}
	for k, v := range meta {
		if !isDomainKey(k) {
			extra[k] = v
		}
	}

	if id == "" {
		id = meta["id"]
	}
	milestone := meta["milestone"]
	if milestone == "none" {
		milestone = ""
	}
	state := meta["state"]
	if state == "" {
		state = "open"
	}
	origin := meta["origin"]
	if origin == "" {
		origin = Local
	}

	return &Issue{
		ID:        id,
		Title:     title,
		Body:      strings.TrimSpace(body),
		State:     state,
		Labels:    splitList(meta["labels"]),
		Assignees: splitList(meta["assignees"]),
		Milestone: milestone,
		Depends:   splitList(meta["depends"]),
		Origin:    origin,
		Extra:     extra,
	}
}

// Text renders the issue back to its canonical file form.
func (i *Issue) Text() string {
	meta := map[string]string{}
	for k, v := range i.Extra {
		meta[k] = v
	}
	milestone := i.Milestone
	if milestone == "" {
		milestone = "none"
	}
	meta["id"] = i.ID
	meta["state"] = i.State
	meta["labels"] = renderList(i.Labels)
	meta["assignees"] = renderList(i.Assignees)
	meta["milestone"] = milestone
	meta["depends"] = renderList(i.Depends)
	meta["origin"] = i.Origin

	body := strings.TrimSpace(i.Body)
	if body == "" {
		body = "(no body)"
	}
	return fmt.Sprintf("%s\n# %s\n\n%s\n", RenderMeta(meta), i.Title, body)
}

// Slugify turns a title into an id. Titles are English by format rule, so
// ASCII is enough; anything else is dropped rather than transliterated.
func Slugify(text string, maxLen int) string {
	if maxLen <= 0 {
		maxLen = 48
	}
	s := strings.Trim(slugPunct.ReplaceAllString(strings.ToLower(text), "-"), "-")
	if len(s) > maxLen {
		cut := s[:maxLen]
		if i := strings.LastIndex(cut, "-"); i > 0 {
			cut = cut[:i]
		}
		s = cut
	}
	s = strings.Trim(s, "-")
	if s == "" {
		return "issue"
	}
	return s
}

// IsSlug reports whether id is a well-formed identity.
func IsSlug(id string) bool { return slugOK.MatchString(id) }

// UniqueID is base, or base-2, base-3… when the slug is already used.
func UniqueID(root, base string, taken []string) (string, error) {
	used := map[string]bool{}
	for _, t := range taken {
		used[t] = true
	}
	for _, t := range AllIDs(root) {
		used[t] = true
	}
	if !used[base] {
		return base, nil
	}
	for n := 2; n < 1000; n++ {
		cand := fmt.Sprintf("%s-%d", base, n)
		if !used[cand] {
			return cand, nil
		}
	}
	return "", fmt.Errorf("cannot allocate an id for %q", base)
}

func isDomainKey(k string) bool {
	for _, d := range DomainKeys {
		if d == k {
			return true
		}
	}
	return false
}