// Package fakeredmine is a stateful in-memory Redmine REST fake used by
// the test suite and the smoke run. The real tracker is NEVER contacted.
// It implements exactly the endpoints the redmine client uses, enforces
// X-Redmine-API-Key auth on every one of them, and records every request
// so tests can assert round-trips. Error responses deliberately echo the
// presented key back in the body: any test that survives that proves the
// client never surfaces response bodies (key-redaction guarantee).
package fakeredmine

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"sync"
)

// Request is one recorded exchange (auth checked, body captured).
type Request struct {
	Method string
	Path   string // path without query
	Query  string // raw query
	Body   string
}

// Version is the roadmap-milestone shape.
type Version struct {
	ID       int    `json:"id"`
	Name     string `json:"name"`
	DueDate  string `json:"due_date,omitempty"`
	Status   string `json:"status"` // open|locked|closed
	Sharing  string `json:"sharing,omitempty"`
}

// Category is the issue-category shape.
type Category struct {
	ID   int    `json:"id"`
	Name string `json:"name"`
}

// JournalEntry is one history note.
type JournalEntry struct {
	ID       int    `json:"id"`
	UserID   int    `json:"user_id"`
	Notes    string `json:"notes"`
	CreatedOn string `json:"created_on"`
}

// Issue is the stored issue (server side, write-friendly scalars).
type Issue struct {
	ID               int      `json:"id"`
	Subject          string   `json:"subject"`
	Description      string   `json:"description"`
	ProjectID        string   `json:"project_id"`
	TrackerID        int      `json:"tracker_id"`
	StatusID         int      `json:"status_id"`
	PriorityID       int      `json:"priority_id"`
	CategoryID       int      `json:"category_id,omitempty"`
	FixedVersionID   int      `json:"fixed_version_id,omitempty"`
	ParentIssueID    int      `json:"parent_issue_id,omitempty"`
	EstimatedHours   *float64 `json:"estimated_hours,omitempty"`
	DoneRatio        int      `json:"done_ratio,omitempty"`
	DueDate          string   `json:"due_date,omitempty"`
	Notes            string   `json:"notes,omitempty"` // write-only: create/update note -> journal
	CreatedOn        string   `json:"created_on"`
	UpdatedOn        string   `json:"updated_on"`
	Journals         []JournalEntry `json:"journals,omitempty"`
}

// Relation is the issue-relation shape.
type Relation struct {
	ID           int    `json:"id"`
	IssueID      int    `json:"issue_id"`
	IssueToID    int    `json:"issue_to_id"`
	RelationType string `json:"relation_type"`
	Delay        int    `json:"delay,omitempty"`
}

// Server is the fake Redmine.
type Server struct {
	URL       string
	APIKey    string
	apiKeySet bool

	mu         sync.Mutex
	srv        *httptest.Server
	requests   []Request
	issues     map[int]*Issue
	versions   map[int]Version
	categories map[int]Category
	relations  map[int]Relation
	nextID     int
	// Fail, when non-nil, is returned instead of normal handling; it is
	// consumed by the first request that sees it.
	Fail *FailSpec

	Trackers  []IDName
	Statuses  []Status
	Priorities []IDName
}

// FailSpec pins the next response (error-mapping tests).
type FailSpec struct {
	Status int
	Body   string
}

// IDName is a bare enumeration entry.
type IDName struct {
	ID   int    `json:"id"`
	Name string `json:"name"`
}

// Status adds the is_closed flag to an enumeration entry.
type Status struct {
	ID       int    `json:"id"`
	Name     string `json:"name"`
	IsClosed bool   `json:"is_closed"`
}

// New starts a fake on a random port with Redmine's default
// enumerations and an empty MOPAC project.
func New(apiKey string) *Server {
	s := &Server{
		APIKey:     apiKey,
		apiKeySet:  true,
		issues:     map[int]*Issue{},
		versions:   map[int]Version{},
		categories: map[int]Category{},
		relations:  map[int]Relation{},
		nextID:     100,
		Trackers: []IDName{
			{1, "Bug"}, {2, "Feature"}, {3, "Support"}, {4, "Task"},
		},
		Statuses: []Status{
			{1, "New", false}, {2, "In Progress", false},
			{3, "Done", true}, {4, "Rejected", true},
		},
		Priorities: []IDName{
			{1, "Low"}, {2, "Normal"}, {3, "High"}, {4, "Urgent"}, {5, "Immediate"},
		},
	}
	mux := http.NewServeMux()
	mux.HandleFunc("/", s.handler)
	s.srv = httptest.NewServer(mux)
	s.URL = s.srv.URL
	return s
}

// Close shuts the fake down.
func (s *Server) Close() { s.srv.Close() }

// Requests returns a copy of the recorded exchanges.
func (s *Server) Requests() []Request {
	s.mu.Lock()
	defer s.mu.Unlock()
	out := make([]Request, len(s.requests))
	copy(out, s.requests)
	return out
}

// AddIssue seeds an issue directly (bypassing REST) and returns its id.
func (s *Server) AddIssue(i Issue) int {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.nextID++
	i.ID = s.nextID
	now := "2026-08-29T12:00:00Z"
	if i.CreatedOn == "" {
		i.CreatedOn = now
	}
	if i.UpdatedOn == "" {
		i.UpdatedOn = now
	}
	s.issues[i.ID] = &i
	return i.ID
}

// Issue returns a deep-ish copy of a stored issue (for assertions).
func (s *Server) Issue(id int) (Issue, bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	i, ok := s.issues[id]
	if !ok {
		return Issue{}, false
	}
	return *i, true
}

// AddVersion / AddCategory seed enumerations directly.
func (s *Server) AddVersion(v Version) int {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.nextID++
	v.ID = s.nextID
	s.versions[v.ID] = v
	return v.ID
}

func (s *Server) AddCategory(name string) int {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.nextID++
	s.categories[s.nextID] = Category{ID: s.nextID, Name: name}
	return s.nextID
}

func (s *Server) handler(w http.ResponseWriter, r *http.Request) {
	key := ""
	if s.apiKeySet {
		key = r.Header.Get("X-Redmine-API-Key")
	}
	body, _ := io.ReadAll(io.LimitReader(r.Body, 1<<20))

	s.mu.Lock()
	if s.Fail != nil {
		spec := *s.Fail
		s.Fail = nil
		s.requests = append(s.requests, Request{r.Method, r.URL.Path, r.URL.RawQuery, string(body)})
		s.mu.Unlock()
		// The body deliberately embeds the presented key: surviving this
		// proves the client drops response bodies from error strings.
		w.WriteHeader(spec.Status)
		fmt.Fprintf(w, spec.Body, key)
		return
	}
	if s.apiKeySet && key != s.APIKey {
		s.requests = append(s.requests, Request{r.Method, r.URL.Path, r.URL.RawQuery, ""})
		s.mu.Unlock()
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusUnauthorized)
		fmt.Fprintf(w, `{"errors":["Invalid HTTP auth: key %s was rejected"]}`, key)
		return
	}
	s.requests = append(s.requests, Request{r.Method, r.URL.Path, r.URL.RawQuery, string(body)})

	var (
		respStatus = http.StatusOK
		respBody   string
	)
	path := r.URL.Path
	q := r.URL.Query()
	switch {
	case r.Method == http.MethodGet && path == "/issues.json":
		respStatus, respBody = s.listIssues(q)
	case r.Method == http.MethodGet && strings.HasPrefix(path, "/issues/") && strings.HasSuffix(path, ".json"):
		id, _ := strconv.Atoi(strings.TrimSuffix(strings.TrimPrefix(path, "/issues/"), ".json"))
		respStatus, respBody = s.getIssue(id, q.Get("include"))
	case r.Method == http.MethodPost && path == "/issues.json":
		respStatus, respBody = s.createIssue(body)
	case r.Method == http.MethodPut && strings.HasPrefix(path, "/issues/") && strings.HasSuffix(path, ".json"):
		id, _ := strconv.Atoi(strings.TrimSuffix(strings.TrimPrefix(path, "/issues/"), ".json"))
		respStatus, respBody = s.updateIssue(id, body)
	case r.Method == http.MethodPost && strings.HasSuffix(path, "/relations.json"):
		from, _ := strconv.Atoi(strings.TrimSuffix(strings.TrimPrefix(path, "/issues/"), "/relations.json"))
		respStatus, respBody = s.createRelation(from, body)
	case r.Method == http.MethodGet && strings.HasPrefix(path, "/projects/") && strings.HasSuffix(path, "/versions.json"):
		respStatus, respBody = s.listVersions()
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/projects/") && strings.HasSuffix(path, "/versions.json"):
		respStatus, respBody = s.createVersion(body)
	case r.Method == http.MethodGet && strings.HasPrefix(path, "/projects/") && strings.HasSuffix(path, "/issue_categories.json"):
		respStatus, respBody = s.listCategories()
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/projects/") && strings.HasSuffix(path, "/issue_categories.json"):
		respStatus, respBody = s.createCategory(body)
	case r.Method == http.MethodGet && path == "/trackers.json":
		respStatus, respBody = jsonReply(map[string]any{"trackers": s.Trackers})
	case r.Method == http.MethodGet && path == "/issue_statuses.json":
		respStatus, respBody = jsonReply(map[string]any{"issue_statuses": s.Statuses})
	case r.Method == http.MethodGet && path == "/enumerations/issue_priorities.json":
		respStatus, respBody = jsonReply(map[string]any{"issue_priorities": s.Priorities})
	default:
		respStatus, respBody = http.StatusNotFound, `{"errors":["Not found"]}`
	}
	s.mu.Unlock()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(respStatus)
	if respBody != "" {
		io.WriteString(w, respBody)
	}
}

func jsonReply(v any) (int, string) {
	b, err := json.Marshal(v)
	if err != nil {
		return http.StatusInternalServerError, `{"errors":["marshal"]}`
	}
	return http.StatusOK, string(b)
}

func (s *Server) listIssues(q url.Values) (int, string) {
	// Redmine defaults to OPEN issues only; status_id=* lifts it.
	wantStatus := "open"
	if v := q.Get("status_id"); v != "" {
		wantStatus = v
	}
	var proj, ver string
	proj = q.Get("project_id")
	ver = q.Get("fixed_version_id")
	limit := 25
	if v := q.Get("limit"); v != "" {
		if n, err := strconv.Atoi(v); err == nil {
			limit = n
		}
	}
	type out struct {
		Issues    []map[string]any `json:"issues"`
		Total     int              `json:"total_count"`
		Offset    int              `json:"offset"`
		Limit     int              `json:"limit"`
	}
	o := out{Limit: limit}
	var ids []int
	for id, i := range s.issues {
		if proj != "" && i.ProjectID != proj {
			continue
		}
		if wantStatus == "open" && s.statusIsClosed(i.StatusID) {
			continue
		}
		if wantStatus == "closed" && !s.statusIsClosed(i.StatusID) {
			continue
		}
		if ver != "" && strconv.Itoa(i.FixedVersionID) != ver {
			continue
		}
		ids = append(ids, id)
	}
	sort.Ints(ids)
	for _, id := range ids {
		o.Issues = append(o.Issues, issueView(s, *s.issues[id], false))
	}
	o.Total = len(o.Issues)
	if len(o.Issues) > limit {
		o.Issues = o.Issues[:limit]
	}
	return jsonReply(o)
}

func (s *Server) statusIsClosed(id int) bool {
	for _, st := range s.Statuses {
		if st.ID == id {
			return st.IsClosed
		}
	}
	return false
}

func (s *Server) getIssue(id int, include string) (int, string) {
	i, ok := s.issues[id]
	if !ok {
		return http.StatusNotFound, `{"errors":["Issue not found"]}`
	}
	out := map[string]any{"issue": issueView(s, *i, include == "journals")}
	return jsonReply(out)
}

func (s *Server) createIssue(body []byte) (int, string) {
	var p struct {
		Issue Issue `json:"issue"`
	}
	if err := json.Unmarshal(body, &p); err != nil {
		return http.StatusBadRequest, `{"errors":["bad json"]}`
	}
	if p.Issue.Subject == "" || p.Issue.ProjectID == "" {
		return http.StatusUnprocessableEntity, `{"errors":["Subject and project cannot be blank"]}`
	}
	s.nextID++
	i := p.Issue
	i.ID = s.nextID
	i.CreatedOn = "2026-08-29T12:00:00Z"
	i.UpdatedOn = i.CreatedOn
	if i.Notes != "" { // notes on create become the first journal
		i.Journals = append(i.Journals, JournalEntry{ID: 1, UserID: 5, Notes: i.Notes, CreatedOn: i.CreatedOn})
	}
	s.issues[i.ID] = &i
	return http.StatusCreated, `{"issue":` + mustJSON(issueView(s, i, false)) + `}`
}

func (s *Server) updateIssue(id int, body []byte) (int, string) {
	i, ok := s.issues[id]
	if !ok {
		return http.StatusNotFound, `{"errors":["Issue not found"]}`
	}
	var p struct {
		Issue Issue `json:"issue"`
	}
	if err := json.Unmarshal(body, &p); err != nil {
		return http.StatusBadRequest, `{"errors":["bad json"]}`
	}
	if p.Issue.Subject != "" {
		i.Subject = p.Issue.Subject
	}
	if p.Issue.Description != "" {
		i.Description = p.Issue.Description
	}
	if p.Issue.TrackerID != 0 {
		i.TrackerID = p.Issue.TrackerID
	}
	if p.Issue.StatusID != 0 {
		i.StatusID = p.Issue.StatusID
	}
	if p.Issue.PriorityID != 0 {
		i.PriorityID = p.Issue.PriorityID
	}
	if p.Issue.CategoryID != 0 {
		i.CategoryID = p.Issue.CategoryID
	}
	if p.Issue.FixedVersionID != 0 {
		i.FixedVersionID = p.Issue.FixedVersionID
	}
	if p.Issue.EstimatedHours != nil {
		i.EstimatedHours = p.Issue.EstimatedHours
	}
	if p.Issue.DoneRatio != 0 {
		i.DoneRatio = p.Issue.DoneRatio
	}
	if p.Issue.DueDate != "" {
		i.DueDate = p.Issue.DueDate
	}
	if p.Issue.Notes != "" {
		i.Journals = append(i.Journals, JournalEntry{
			ID: len(i.Journals) + 1, UserID: 5, Notes: p.Issue.Notes, CreatedOn: "2026-08-29T13:00:00Z",
		})
	}
	i.UpdatedOn = "2026-08-29T13:00:00Z"
	return http.StatusNoContent, ""
}

func (s *Server) createRelation(from int, body []byte) (int, string) {
	var p struct {
		Relation Relation `json:"relation"`
	}
	if err := json.Unmarshal(body, &p); err != nil {
		return http.StatusBadRequest, `{"errors":["bad json"]}`
	}
	if _, ok := s.issues[from]; !ok {
		return http.StatusNotFound, `{"errors":["Issue not found"]}`
	}
	if _, ok := s.issues[p.Relation.IssueToID]; !ok {
		return http.StatusUnprocessableEntity, `{"errors":["Issue not found"]}`
	}
	t := p.Relation.RelationType
	if t != "blocks" && t != "relates" && t != "precedes" && t != "copied_to" && t != "duplicates" {
		return http.StatusUnprocessableEntity, `{"errors":["relation_type is not included in the list"]}`
	}
	s.nextID++
	rel := Relation{ID: s.nextID, IssueID: from, IssueToID: p.Relation.IssueToID, RelationType: t}
	s.relations[rel.ID] = rel
	return http.StatusCreated, `{"relation":` + mustJSON(rel) + `}`
}

func (s *Server) listVersions() (int, string) {
	var vs []Version
	for _, v := range s.versions {
		vs = append(vs, v)
	}
	return jsonReply(map[string]any{"versions": vs})
}

func (s *Server) createVersion(body []byte) (int, string) {
	var p struct {
		Version Version `json:"version"`
	}
	if err := json.Unmarshal(body, &p); err != nil {
		return http.StatusBadRequest, `{"errors":["bad json"]}`
	}
	if p.Version.Name == "" {
		return http.StatusUnprocessableEntity, `{"errors":["Name cannot be blank"]}`
	}
	for _, v := range s.versions {
		if v.Name == p.Version.Name {
			return http.StatusUnprocessableEntity, `{"errors":["Name has already been taken"]}`
		}
	}
	s.nextID++
	v := p.Version
	v.ID = s.nextID
	if v.Status == "" {
		v.Status = "open"
	}
	s.versions[v.ID] = v
	return http.StatusCreated, `{"version":` + mustJSON(v) + `}`
}

func (s *Server) listCategories() (int, string) {
	var cs []Category
	for _, c := range s.categories {
		cs = append(cs, c)
	}
	return jsonReply(map[string]any{"issue_categories": cs})
}

func (s *Server) createCategory(body []byte) (int, string) {
	var p struct {
		Category Category `json:"issue_category"`
	}
	if err := json.Unmarshal(body, &p); err != nil {
		return http.StatusBadRequest, `{"errors":["bad json"]}`
	}
	if p.Category.Name == "" {
		return http.StatusUnprocessableEntity, `{"errors":["Name cannot be blank"]}`
	}
	for _, c := range s.categories {
		if c.Name == p.Category.Name {
			return http.StatusUnprocessableEntity, `{"errors":["Name has already been taken"]}`
		}
	}
	s.nextID++
	c := Category{ID: s.nextID, Name: p.Category.Name}
	s.categories[c.ID] = c
	return http.StatusCreated, `{"issue_category":` + mustJSON(c) + `}`
}

// issueView projects the stored issue into Redmine's READ shape
// (nested objects for project/tracker/status/priority/category/version).
func issueView(s *Server, i Issue, withJournals bool) map[string]any {
	v := map[string]any{
		"id":           i.ID,
		"subject":      i.Subject,
		"description":  i.Description,
		"created_on":   i.CreatedOn,
		"updated_on":   i.UpdatedOn,
	}
	v["project"] = map[string]any{"id": 1, "name": i.ProjectID, "identifier": i.ProjectID}
	if n := enumName(s.Trackers, i.TrackerID); n != "" {
		v["tracker"] = map[string]any{"id": i.TrackerID, "name": n}
	}
	if st := statusByID(s.Statuses, i.StatusID); st != nil {
		v["status"] = map[string]any{"id": st.ID, "name": st.Name, "is_closed": st.IsClosed}
	}
	if n := enumName(s.Priorities, i.PriorityID); n != "" {
		v["priority"] = map[string]any{"id": i.PriorityID, "name": n}
	}
	if i.CategoryID != 0 {
		if c, ok := s.categories[i.CategoryID]; ok {
			v["category"] = map[string]any{"id": c.ID, "name": c.Name}
		}
	}
	if i.FixedVersionID != 0 {
		if ver, ok := s.versions[i.FixedVersionID]; ok {
			v["fixed_version"] = map[string]any{"id": ver.ID, "name": ver.Name}
		}
	}
	if i.ParentIssueID != 0 {
		v["parent"] = map[string]any{"id": i.ParentIssueID}
	}
	if i.EstimatedHours != nil {
		v["estimated_hours"] = *i.EstimatedHours
	}
	if i.DoneRatio != 0 {
		v["done_ratio"] = i.DoneRatio
	}
	if i.DueDate != "" {
		v["due_date"] = i.DueDate
	}
	if withJournals && len(i.Journals) > 0 {
		v["journals"] = i.Journals
	}
	return v
}

func enumName(list []IDName, id int) string {
	for _, e := range list {
		if e.ID == id {
			return e.Name
		}
	}
	return ""
}

func statusByID(list []Status, id int) *Status {
	for i := range list {
		if list[i].ID == id {
			return &list[i]
		}
	}
	return nil
}

func mustJSON(v any) string {
	b, err := json.Marshal(v)
	if err != nil {
		panic(err)
	}
	return string(b)
}