package service

import (
	"context"
	"fmt"
	"net/url"
	"strconv"
	"strings"

	"github.com/krow/krow-backend/go-api/internal/authctx"
	"github.com/krow/krow-backend/go-api/internal/definition"
	"github.com/krow/krow-backend/go-api/internal/domain"
	"github.com/krow/krow-backend/go-api/internal/repo"
)

// allowedDefinitionFilters names the accepted query parameters for definition collections.
var allowedDefinitionFilters = map[string]bool{
	"visibility":    true,
	"status":        true,
	"definition_id": true,
	"sort":          true,
	"limit":         true,
	"offset":        true,
}

// DefinitionsService manages authored Agent and Skill definitions.
type DefinitionsService struct {
	repo *repo.DefinitionsRepo

	// versions is the append-only history beside the editable definition.
	// Written on publish, never on save — see snapshotIfPublished.
	versions *repo.VersionsRepo

	// unknownTools reports which of a spec's tool names are not registered.
	// nil means no check — the shipped importer path, which has its own.
	unknownTools func([]string) []string
}

// NewDefinitions builds a definitions service over a repository.
func NewDefinitions(db repo.Querier) *DefinitionsService {
	return &DefinitionsService{
		repo:     repo.NewDefinitionsRepo(db),
		versions: repo.NewVersionsRepo(db),
	}
}

// WithToolCheck teaches the service which tool names exist.
//
// §3 requires an unknown tool name to fail validation at PUBLISH. Without it
// the runtime records the name and drops it, so a typo produces an agent that
// is silently missing a capability its author believes it has — and the author
// finds out by watching it fail to answer.
//
// Injected rather than imported so this package does not depend on the tool
// registry, and so a test can supply its own vocabulary.
func (s *DefinitionsService) WithToolCheck(unknown func([]string) []string) *DefinitionsService {
	s.unknownTools = unknown
	return s
}

// rejectUnknownTools fails a definition that names a tool that does not exist.
func (s *DefinitionsService) rejectUnknownTools(markdown string) error {
	if s.unknownTools == nil {
		return nil
	}
	agent, err := definition.ParseAgent(markdown, definition.Options{})
	if err != nil || agent == nil {
		// ValidateAgent has already run and reported anything real; a parse
		// failure here is not a second opinion worth raising.
		return nil
	}
	if bad := s.unknownTools(agent.Tools); len(bad) > 0 {
		return domain.Validation(
			fmt.Sprintf("unknown tool(s): %s", strings.Join(bad, ", ")),
			map[string]string{"tools": strings.Join(bad, ", ")})
	}
	return nil
}

// ParseListParams validates query parameters for listing definitions.
func (s *DefinitionsService) ParseListParams(q url.Values) (repo.DefinitionListParams, error) {
	p := repo.DefinitionListParams{
		Limit: 100,
		Sort:  "created_date",
		Desc:  true,
	}

	for name := range q {
		if !allowedDefinitionFilters[name] {
			return p, domain.Invalid(fmt.Sprintf("unknown filter field %q", name))
		}
	}

	if raw := q.Get("visibility"); raw != "" {
		if raw != "personal" && raw != "organization" {
			return p, domain.Invalid("visibility must be one of: personal, organization")
		}
		p.Visibility = raw
	}

	if raw := q.Get("status"); raw != "" {
		p.Status = raw
	}

	if raw := q.Get("definition_id"); raw != "" {
		p.DefinitionID = raw
	}

	if raw := q.Get("sort"); raw != "" {
		field := raw
		desc := false
		if strings.HasPrefix(field, "-") {
			desc = true
			field = field[1:]
		}
		switch field {
		case "created_date", "updated_date", "name", "definition_id", "status", "version":
			p.Sort = field
			p.Desc = desc
		default:
			return p, domain.Invalid(fmt.Sprintf("cannot sort by %q", field))
		}
	}

	if raw := q.Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n < 0 {
			return p, domain.Invalid("limit must be a non-negative integer")
		}
		if n > MaxLimit {
			n = MaxLimit
		}
		p.Limit = n
	}

	if raw := q.Get("offset"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n < 0 {
			return p, domain.Invalid("offset must be a non-negative integer")
		}
		p.Offset = n
	}

	return p, nil
}

/* ── Agents ─────────────────────────────────────────────────────────────── */

// ListAgents returns a page of authored agent definitions.
func (s *DefinitionsService) ListAgents(ctx context.Context, ident authctx.Identity, p repo.DefinitionListParams) (*domain.Page, error) {
	records, total, err := s.repo.ListAgents(ctx, ident, p)
	if err != nil {
		return nil, err
	}
	if records == nil {
		records = []domain.Record{}
	}
	return &domain.Page{
		Records: records,
		Total:   total,
		Limit:   p.Limit,
		Offset:  p.Offset,
	}, nil
}

// GetAgent returns one agent definition by id within the caller's tenant and ownership scope.
func (s *DefinitionsService) GetAgent(ctx context.Context, ident authctx.Identity, id string) (domain.Record, error) {
	if !isUUID(id) {
		return nil, domain.NotFound("AgentDefinition", id)
	}
	rec, err := s.repo.GetAgent(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if rec == nil {
		return nil, domain.NotFound("AgentDefinition", id)
	}
	return rec, nil
}

// CreateAgent validates, parses and persists a new authored agent definition.
func (s *DefinitionsService) CreateAgent(ctx context.Context, ident authctx.Identity, body domain.Record) (domain.Record, error) {
	mdRaw, ok := body["markdown"]
	if !ok || mdRaw == nil {
		return nil, domain.Validation("Paste or upload a Markdown definition.", nil)
	}
	markdown, isStr := mdRaw.(string)
	if !isStr {
		return nil, domain.Validation("markdown must be a string", nil)
	}

	if err := definition.ValidateAgent(markdown); err != nil {
		return nil, domain.Validation(err.Error(), nil)
	}
	if err := s.rejectUnknownTools(markdown); err != nil {
		return nil, err
	}

	visibility := "personal"
	if visRaw, ok := body["visibility"]; ok && visRaw != nil {
		v, isStr := visRaw.(string)
		if !isStr || (v != "personal" && v != "organization") {
			return nil, domain.Validation("visibility must be one of: personal, organization", map[string]string{"visibility": "invalid"})
		}
		visibility = v
	}

	if visibility == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	agent, err := definition.ParseAgent(markdown, definition.Options{})
	if err != nil {
		return nil, domain.Validation("That definition could not be parsed. "+err.Error(), nil)
	}

	input := repo.AgentInsertInput{
		DefinitionID: agent.ID,
		OrgID:        ident.OrgID,
		Visibility:   visibility,
		CreatedBy:    &ident.UserID,
		Markdown:     markdown,
		Status:       agent.Status,
		Version:      agent.Version,
		Name:         agent.Name,
		Description:  agent.Description,
		Pages:        agent.Pages,
	}

	if visibility == "personal" {
		input.OwnerUserID = &ident.UserID
	}

	if err := s.refuseVersionGoingBackwards(ctx, ident, repo.KindAgent,
		agent.ID, agent.Status, agent.Version); err != nil {
		return nil, err
	}
	if err := s.refuseSubagentCycle(ctx, ident, agent.ID, agent.Subagents); err != nil {
		return nil, err
	}
	if err := s.refusePublishedRewrite(ctx, ident, repo.KindAgent,
		agent.ID, markdown, agent.Status, agent.Version); err != nil {
		return nil, err
	}

	rec, err := s.repo.InsertAgent(ctx, ident, input)
	if err != nil {
		return nil, err
	}
	// Recorded after the row exists, and never allowed to fail the save: the
	// author's work is already stored, and losing it to protect a record of it
	// would be the wrong trade.
	_ = s.snapshotIfPublished(ctx, ident, repo.KindAgent, rec)
	return rec, nil
}

// UpdateAgent validates and applies updates to an authored agent definition.
func (s *DefinitionsService) UpdateAgent(ctx context.Context, ident authctx.Identity, id string, patch domain.Record) (domain.Record, error) {
	if !isUUID(id) {
		return nil, domain.NotFound("AgentDefinition", id)
	}

	existing, err := s.repo.GetAgent(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if existing == nil {
		return nil, domain.NotFound("AgentDefinition", id)
	}

	if existing["visibility"] == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	if visRaw, ok := patch["visibility"]; ok && visRaw != nil {
		if v, isStr := visRaw.(string); isStr && v != existing["visibility"] {
			return nil, domain.Validation("visibility cannot be modified after creation", map[string]string{"visibility": "immutable"})
		}
	}

	var input repo.AgentUpdateInput

	if mdRaw, ok := patch["markdown"]; ok && mdRaw != nil {
		markdown, isStr := mdRaw.(string)
		if !isStr {
			return nil, domain.Validation("markdown must be a string", nil)
		}
		if err := definition.ValidateAgent(markdown); err != nil {
			return nil, domain.Validation(err.Error(), nil)
		}
		if err := s.rejectUnknownTools(markdown); err != nil {
			return nil, err
		}
		agent, err := definition.ParseAgent(markdown, definition.Options{})
		if err != nil {
			return nil, domain.Validation("That definition could not be parsed. "+err.Error(), nil)
		}
		input.Markdown = &markdown
		input.DefinitionID = &agent.ID
		input.Name = &agent.Name
		input.Description = &agent.Description
		input.Status = &agent.Status
		input.Version = &agent.Version
		input.Pages = agent.Pages

		if err := s.refuseVersionGoingBackwards(ctx, ident, repo.KindAgent,
			agent.ID, agent.Status, agent.Version); err != nil {
			return nil, err
		}
		if err := s.refuseSubagentCycle(ctx, ident, agent.ID, agent.Subagents); err != nil {
			return nil, err
		}
		if err := s.refusePublishedRewrite(ctx, ident, repo.KindAgent,
			agent.ID, markdown, agent.Status, agent.Version); err != nil {
			return nil, err
		}
	} else if statusRaw, ok := patch["status"]; ok && statusRaw != nil {
		status, isStr := statusRaw.(string)
		if !isStr || (status != "draft" && status != "published" && status != "archived") {
			return nil, domain.Validation("status must be one of: draft, published, archived", map[string]string{"status": "invalid"})
		}
		input.Status = &status
	}

	rec, err := s.repo.UpdateAgent(ctx, ident, id, input)
	if err != nil {
		return nil, err
	}
	_ = s.snapshotIfPublished(ctx, ident, repo.KindAgent, rec)
	return rec, nil
}

// DeleteAgent removes an agent definition following idempotent delete semantics.
func (s *DefinitionsService) DeleteAgent(ctx context.Context, ident authctx.Identity, id string) (domain.Record, error) {
	if !isUUID(id) {
		return domain.Record{"id": id}, nil
	}

	existing, err := s.repo.GetAgent(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if existing == nil {
		return domain.Record{"id": id}, nil
	}

	if existing["visibility"] == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	if _, err := s.repo.DeleteAgent(ctx, ident, id); err != nil {
		return nil, err
	}
	return domain.Record{"id": id}, nil
}

/* ── Skills ─────────────────────────────────────────────────────────────── */

// ListSkills returns a page of authored skill definitions.
func (s *DefinitionsService) ListSkills(ctx context.Context, ident authctx.Identity, p repo.DefinitionListParams) (*domain.Page, error) {
	records, total, err := s.repo.ListSkills(ctx, ident, p)
	if err != nil {
		return nil, err
	}
	if records == nil {
		records = []domain.Record{}
	}
	return &domain.Page{
		Records: records,
		Total:   total,
		Limit:   p.Limit,
		Offset:  p.Offset,
	}, nil
}

// GetSkill returns one skill definition by id within the caller's tenant and ownership scope.
func (s *DefinitionsService) GetSkill(ctx context.Context, ident authctx.Identity, id string) (domain.Record, error) {
	if !isUUID(id) {
		return nil, domain.NotFound("SkillDefinition", id)
	}
	rec, err := s.repo.GetSkill(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if rec == nil {
		return nil, domain.NotFound("SkillDefinition", id)
	}
	return rec, nil
}

// CreateSkill validates, parses and persists a new authored skill definition.
func (s *DefinitionsService) CreateSkill(ctx context.Context, ident authctx.Identity, body domain.Record) (domain.Record, error) {
	mdRaw, ok := body["markdown"]
	if !ok || mdRaw == nil {
		return nil, domain.Validation("Paste or upload a Markdown definition.", nil)
	}
	markdown, isStr := mdRaw.(string)
	if !isStr {
		return nil, domain.Validation("markdown must be a string", nil)
	}

	if err := definition.ValidateSkill(markdown); err != nil {
		return nil, domain.Validation(err.Error(), nil)
	}

	visibility := "personal"
	if visRaw, ok := body["visibility"]; ok && visRaw != nil {
		v, isStr := visRaw.(string)
		if !isStr || (v != "personal" && v != "organization") {
			return nil, domain.Validation("visibility must be one of: personal, organization", map[string]string{"visibility": "invalid"})
		}
		visibility = v
	}

	if visibility == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	skill, err := definition.ParseSkill(markdown, definition.Options{})
	if err != nil {
		return nil, domain.Validation("That definition could not be parsed. "+err.Error(), nil)
	}

	input := repo.SkillInsertInput{
		DefinitionID: skill.ID,
		OrgID:        ident.OrgID,
		Visibility:   visibility,
		CreatedBy:    &ident.UserID,
		Markdown:     markdown,
		Status:       skill.Status,
		Name:         skill.Name,
		Description:  skill.Description,
		Pages:        skill.Pages,
	}

	if visibility == "personal" {
		input.OwnerUserID = &ident.UserID
	}

	rec, err := s.repo.InsertSkill(ctx, ident, input)
	if err != nil {
		return nil, err
	}
	_ = s.snapshotSkill(ctx, ident, rec)
	return rec, nil
}

// UpdateSkill validates and applies updates to an authored skill definition.
func (s *DefinitionsService) UpdateSkill(ctx context.Context, ident authctx.Identity, id string, patch domain.Record) (domain.Record, error) {
	if !isUUID(id) {
		return nil, domain.NotFound("SkillDefinition", id)
	}

	existing, err := s.repo.GetSkill(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if existing == nil {
		return nil, domain.NotFound("SkillDefinition", id)
	}

	if existing["visibility"] == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	if visRaw, ok := patch["visibility"]; ok && visRaw != nil {
		if v, isStr := visRaw.(string); isStr && v != existing["visibility"] {
			return nil, domain.Validation("visibility cannot be modified after creation", map[string]string{"visibility": "immutable"})
		}
	}

	var input repo.SkillUpdateInput

	if mdRaw, ok := patch["markdown"]; ok && mdRaw != nil {
		markdown, isStr := mdRaw.(string)
		if !isStr {
			return nil, domain.Validation("markdown must be a string", nil)
		}
		if err := definition.ValidateSkill(markdown); err != nil {
			return nil, domain.Validation(err.Error(), nil)
		}
		skill, err := definition.ParseSkill(markdown, definition.Options{})
		if err != nil {
			return nil, domain.Validation("That definition could not be parsed. "+err.Error(), nil)
		}
		input.Markdown = &markdown
		input.DefinitionID = &skill.ID
		input.Name = &skill.Name
		input.Description = &skill.Description
		input.Status = &skill.Status
		input.Pages = skill.Pages
	} else if statusRaw, ok := patch["status"]; ok && statusRaw != nil {
		status, isStr := statusRaw.(string)
		if !isStr || (status != "active" && status != "inactive") {
			return nil, domain.Validation("status must be one of: active, inactive", map[string]string{"status": "invalid"})
		}
		input.Status = &status
	}

	rec, err := s.repo.UpdateSkill(ctx, ident, id, input)
	if err != nil {
		return nil, err
	}
	_ = s.snapshotSkill(ctx, ident, rec)
	return rec, nil
}

// DeleteSkill removes a skill definition following idempotent delete semantics.
func (s *DefinitionsService) DeleteSkill(ctx context.Context, ident authctx.Identity, id string) (domain.Record, error) {
	if !isUUID(id) {
		return domain.Record{"id": id}, nil
	}

	existing, err := s.repo.GetSkill(ctx, ident, id)
	if err != nil {
		return nil, err
	}
	if existing == nil {
		return domain.Record{"id": id}, nil
	}

	if existing["visibility"] == "organization" {
		role, known := domain.ParseRole(ident.Role)
		if !known || role == domain.RoleTalent {
			return nil, domain.Forbidden()
		}
	}

	if _, err := s.repo.DeleteSkill(ctx, ident, id); err != nil {
		return nil, err
	}
	return domain.Record{"id": id}, nil
}

/* ── Publishing ─────────────────────────────────────────────────────────── */

// refuseVersionGoingBackwards enforces §3's "monotonic".
//
// Nothing enforced it before. A spec edited from an older copy republishes an
// older number whose content still matches what was published under it, so the
// rewrite guard sees no conflict and the deployed agent quietly goes
// backwards — the version in the UI reads 2 while the newest thing anybody
// approved was 3.
func (s *DefinitionsService) refuseVersionGoingBackwards(ctx context.Context,
	ident authctx.Identity, kind repo.VersionKind, definitionID, status string, version int) error {

	if s.versions == nil || status != "published" || definitionID == "" || version < 1 {
		return nil
	}
	latest, err := s.versions.LatestVersion(ctx, ident, kind, definitionID)
	if err != nil || latest == 0 {
		// Unreadable, or nothing published yet. Neither is grounds to refuse a
		// save: the rewrite guard is what protects published text, and this
		// only orders the numbers.
		return nil
	}
	if version < latest {
		return domain.Conflict(definition.ErrVersionWentBackwards(definitionID, latest, version).Error())
	}
	return nil
}

// refuseSubagentCycle enforces §3's DAG at publish.
//
// The graph is every organization-visible agent plus the one being published,
// with the incoming definition standing in for its stored self — otherwise an
// edit that CREATES a cycle is checked against the version that did not have
// one, and passes.
//
// Personal agents are not included. They are invisible to everyone else, so
// they cannot complete a loop for anybody else, and loading them would mean
// reading other people's drafts to validate your own.
func (s *DefinitionsService) refuseSubagentCycle(ctx context.Context,
	ident authctx.Identity, definitionID string, subagents []string) error {

	if len(subagents) == 0 {
		return nil
	}
	rows, _, err := s.repo.ListAgents(ctx, ident, repo.DefinitionListParams{
		Visibility: "organization", Limit: 500,
	})
	if err != nil {
		// A graph we could not read is not a graph we can call cyclic. The
		// runtime depth cap is what holds when this cannot run.
		return nil
	}

	graph := make(map[string][]string, len(rows)+1)
	for _, rec := range rows {
		id, _ := rec["definition_id"].(string)
		markdown, _ := rec["markdown"].(string)
		if id == "" || markdown == "" || id == definitionID {
			continue // the incoming definition replaces its stored self, below
		}
		if parsed, err := definition.ParseAgent(markdown, definition.Options{}); err == nil && parsed != nil {
			graph[id] = parsed.Subagents
		}
	}
	graph[definitionID] = subagents

	if cycle := definition.FindSubagentCycle(graph); cycle != "" {
		return domain.Validation(
			"that would create a delegation cycle: "+cycle+
				". Delegation follows these edges, so a loop is a run that delegates "+
				"until it runs out of budget.",
			map[string]string{"subagents": "cycle"})
	}
	return nil
}

// refusePublishedRewrite fails a publish that would change a version already
// published, BEFORE anything is written.
//
// snapshotIfPublished below deliberately never fails a save: the author's work
// is already stored and losing it to protect a record of it is the wrong trade.
// That is right for a recording failure — the disk, the pool, the network — and
// wrong for exactly one case. When repo.VersionsRepo.Snapshot refuses because
// the version already says something different, that is not the history failing
// to record; it is §3 firing. Swallowing it leaves two different definitions
// both called v2: the live row the runtime serves, and the snapshot the history
// shows. runtime.LoadAgentVersion resolves a pin by returning the CURRENT
// definition whenever the pinned number equals the current one, so the run gets
// the changed text while the audit trail says otherwise.
//
// So the conflict is detected here instead, before the write, where refusing
// costs the author nothing but a version bump. The post-write snapshot keeps
// its original contract for every other kind of failure.
//
// A concurrent publish of the same number with different content can still slip
// past this check and be caught by the unique index afterwards, where it is
// swallowed as before. That leaves the live row ahead of its snapshot, which is
// the pre-existing behaviour and not something this guard makes worse.
func (s *DefinitionsService) refusePublishedRewrite(ctx context.Context, ident authctx.Identity,
	kind repo.VersionKind, definitionID, markdown, status string, version int) error {

	if s.versions == nil || status != "published" || definitionID == "" || version < 1 {
		return nil
	}

	stored, err := s.versions.Load(ctx, ident, kind, definitionID, version)
	if err != nil || stored == nil {
		// Absent (the ordinary case for a new version) or unreadable. Either
		// way there is no published text to contradict, so this is not the
		// place to fail the save.
		return nil
	}
	// Semantic, not textual. The authoring UI re-serialises a definition when
	// it is saved, so a byte comparison refuses a publish over frontmatter key
	// order and a defaulted value written out in full — see
	// definition.SameAgent, which is deliberately conservative about what it
	// treats as inert.
	if definition.SameAgent(stored.Markdown, markdown) {
		return nil // republishing the same version unchanged is a no-op
	}

	return domain.Conflict(fmt.Sprintf(
		"version %d of %q is already published and says something different; "+
			"raise the version in the frontmatter to publish a change",
		version, definitionID))
}

// snapshotIfPublished records an immutable copy when a definition is published.
//
// §3: editing publishes a NEW version, and a published version never changes.
// This is the half that records it. The half that enforces it is a trigger on
// the table, because the repository is not the only thing that can reach it.
//
// ONLY ON PUBLISH. A draft is a work in progress and snapshotting every save
// would fill the history with keystrokes — the version number would stop
// meaning "a thing somebody decided to ship" and start meaning "a time somebody
// pressed save", which is the number a run records and a person has to
// recognise.
//
// A failure here does NOT fail the save. The definition is already written;
// refusing the whole operation because its history could not be recorded would
// lose the author's work to protect a record of it. It is returned so the
// caller can log it, and the missing version shows up as a gap rather than as
// a wrong answer.
func (s *DefinitionsService) snapshotIfPublished(ctx context.Context, ident authctx.Identity,
	kind repo.VersionKind, rec domain.Record) error {

	if s.versions == nil || rec == nil {
		return nil
	}
	status, _ := rec["status"].(string)
	if status != "published" {
		return nil
	}

	markdown, _ := rec["markdown"].(string)
	definitionID, _ := rec["definition_id"].(string)
	if markdown == "" || definitionID == "" {
		return nil
	}

	version := 1
	switch v := rec["version"].(type) {
	case int:
		version = v
	case int32:
		version = int(v)
	case int64:
		version = int(v)
	case float64:
		version = int(v)
	}

	name, _ := rec["name"].(string)
	description, _ := rec["description"].(string)

	return s.versions.Snapshot(ctx, ident, repo.SnapshotInput{
		Kind:         kind,
		DefinitionID: definitionID,
		Version:      version,
		Markdown:     markdown,
		Name:         name,
		Description:  description,
		Pages:        recordPages(rec),
	})
}

// recordPages reads a record's pages, which arrive as []string from the
// repository and as []any when they have been through JSON.
func recordPages(rec domain.Record) []string {
	if raw, ok := rec["pages"].([]string); ok {
		return raw
	}
	raw, ok := rec["pages"].([]any)
	if !ok {
		return nil
	}
	pages := make([]string, 0, len(raw))
	for _, p := range raw {
		if str, isStr := p.(string); isStr {
			pages = append(pages, str)
		}
	}
	return pages
}

// snapshotSkill records an immutable copy of a skill, numbered by the server.
//
// Skills carry no version. An agent's frontmatter names one, so its author
// decides when a change is a new version and can be refused for rewriting an
// old one. A skill has no such field, and giving it one would mean a migration,
// a parser change on BOTH sides of the conformance test in
// internal/definition, and an edit to all 23 shipped skills — a feature, not
// the fix this is.
//
// So the number is the server's: one after whatever was last published. That
// is what repo.VersionsRepo.LatestVersion was written for ("the next published
// version has to follow what was actually published rather than what somebody
// wrote in the frontmatter") and what migration 000010 means by "agents and
// skills version identically". It was built and never wired to anything.
//
// Because the author never names a version, there is nothing here to refuse:
// an edit is always a NEW version, and a save that changed nothing is not a
// version at all. The comparison against the last published copy is what keeps
// the history from filling with keystrokes.
//
// Two simultaneous edits can both compute the same next number; one wins and
// the other's snapshot is dropped, leaving a version unrecorded. That is the
// same narrow race the agent path has, and the same reason it is tolerated
// here: failing an author's save to record it is the wrong trade.
func (s *DefinitionsService) snapshotSkill(ctx context.Context, ident authctx.Identity,
	rec domain.Record) error {

	if s.versions == nil || rec == nil {
		return nil
	}
	// Only a skill that is in service. "inactive" is the skill vocabulary's
	// equivalent of a draft — see definition.SkillStatuses.
	if status, _ := rec["status"].(string); status != "active" {
		return nil
	}

	markdown, _ := rec["markdown"].(string)
	definitionID, _ := rec["definition_id"].(string)
	if markdown == "" || definitionID == "" {
		return nil
	}

	latest, err := s.versions.LatestVersion(ctx, ident, repo.KindSkill, definitionID)
	if err != nil {
		return err
	}
	if latest > 0 {
		stored, err := s.versions.Load(ctx, ident, repo.KindSkill, definitionID, latest)
		if err == nil && stored != nil && definition.SameSkill(stored.Markdown, markdown) {
			return nil // unchanged since the last publish
		}
	}

	name, _ := rec["name"].(string)
	description, _ := rec["description"].(string)

	return s.versions.Snapshot(ctx, ident, repo.SnapshotInput{
		Kind:         repo.KindSkill,
		DefinitionID: definitionID,
		Version:      latest + 1,
		Markdown:     markdown,
		Name:         name,
		Description:  description,
		Pages:        recordPages(rec),
	})
}

// AgentHistory lists an agent's published versions, newest first.
func (s *DefinitionsService) AgentHistory(ctx context.Context, ident authctx.Identity,
	definitionID string, limit int) ([]repo.Version, error) {
	return s.versions.History(ctx, ident, repo.KindAgent, definitionID, limit)
}

// AgentVersion loads one published version of an agent, as it was.
func (s *DefinitionsService) AgentVersion(ctx context.Context, ident authctx.Identity,
	definitionID string, version int) (*repo.Version, error) {
	return s.versions.Load(ctx, ident, repo.KindAgent, definitionID, version)
}