package service

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"

	"git.umbrella.haus/ae/notatest/internal/data"
	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
)

const (
	titleMaxLength     = 150
	initVersionTitle   = "Untitled"
	initVersionContent = ""
)

// Note object context key for incoming requests (handled my middlewares). Only `*data.GetFullNoteRow`
// type objects should be stored behind this key for consistency.
type noteCtxKey struct{}

// Note version object context key for incoming requests (handled by middlewares). Only
// `*data.GetVersionRow` type objects should be stored behind this key for consistency.
type versionCtxKey struct{}

// Mockable database operations interface
type NoteStore interface {
	CreateNote(ctx context.Context, userID uuid.UUID) (data.Note, error)
	DeleteNote(ctx context.Context, arg data.DeleteNoteParams) error
	GetFullNote(ctx context.Context, noteID uuid.UUID) (data.GetFullNoteRow, error)
	ListNotes(ctx context.Context, arg data.ListNotesParams) ([]data.ListNotesRow, error)
	CreateNoteVersion(ctx context.Context, arg data.CreateNoteVersionParams) error
	GetVersion(ctx context.Context, arg data.GetVersionParams) (data.GetVersionRow, error)
	GetVersionHistory(ctx context.Context, arg data.GetVersionHistoryParams) ([]data.GetVersionHistoryRow, error)
}

// Chi HTTP router for notes related CRUD actions.
type notesResource struct {
	Config SvcConfig
	Notes  NoteStore
}

func (rs notesResource) Routes() chi.Router {
	r := chi.NewRouter()

	r.Group(func(r chi.Router) {
		r.Use(requireAccessToken(rs.Config.JWTSecret)) // JWT claims -> ctx.

		r.Post("/", rs.Create)      // POST /notes - create new note
		r.Get("/", rs.ListMetadata) // GET /notes - get all notes (metadata + titles)

		/*
			Clients should utilize `rs.ListMetadata` to load index of user's available notes (e.g.
			sidebar view), use `rs.GetFullNote` to get full notes individually, and if request the
			versioning history with `rs.GetVersionHistory` if necessary (and similarly fetch each
			version individually if the client wants to view them).
		*/

		r.Route(fmt.Sprintf("/{%s}", noteUUIDCtxParameter), func(r chi.Router) {
			r.Use(uuidCtx(noteUUIDCtxParameter))
			r.Use(noteCtx(rs.Notes))                 // DB -> req. context (metadata + active version)
			r.Get("/", rs.GetFullNote)               // GET /notes/{id} - get note from context
			r.Delete("/", rs.Delete)                 // DELETE /notes/{id} - delete note
			r.Get("/versions", rs.GetVersionHistory) // GET /notes/{id}/versions - get full versioning history
			r.Post("/versions", rs.CreateVersion)    // POST /notes/{id}/versions - create new version

			r.Route(fmt.Sprintf("/{%s}", versionUUIDCtxParameter), func(r chi.Router) {
				r.Use(uuidCtx(versionUUIDCtxParameter))
				r.Use(versionCtx(rs.Notes))   // DB -> req. context (scoped version)
				r.Get("/", rs.GetFullVersion) // GET /notes/{id}/{id} - get specific version's contents
			})
		})
	})

	return r
}

// Handler for new note creation. Creates the parent metadata object (`notes` table) and an initial
// placeholder content version (`note_versions` table), and returns the placeholder contents to the
// caller in the HTTP response.
func (rs *notesResource) Create(w http.ResponseWriter, r *http.Request) {
	user, ok := r.Context().Value(userCtxKey{}).(*userClaims)
	if !ok {
		respondError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	userID, err := uuid.Parse(user.Subject)
	if err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid user ID")
		return
	}

	// Metadata object (parent)
	note, err := rs.Notes.CreateNote(r.Context(), userID)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to create note")
		return
	}

	// Initial (empty) placeholder version of the contents
	err = rs.Notes.CreateNoteVersion(r.Context(), data.CreateNoteVersionParams{
		NoteID:      note.ID,
		Title:       initVersionTitle,
		Content:     initVersionContent,
		ContentHash: sha1ContentHash(initVersionTitle, initVersionContent),
	})
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to create initial version")
		return
	}

	// Placeholder contents are decided server-side, so we need to inform the client of them via a
	// one-time-use DTO
	respondJSON(w, http.StatusCreated, map[string]string{
		"title":   initVersionTitle,
		"content": initVersionContent,
	})
}

// Handler for listing the metadata of all user's available notes. This metadata contains IDs of
// the note and its owner, its title, and the time it was last updated.
func (rs *notesResource) ListMetadata(w http.ResponseWriter, r *http.Request) {
	user, ok := r.Context().Value(userCtxKey{}).(*userClaims)
	if !ok {
		respondError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	userID, err := uuid.Parse(user.Subject)
	if err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid user ID")
		return
	}

	limit, offset := getPaginationParams(r)
	notes, err := rs.Notes.ListNotes(r.Context(), data.ListNotesParams{
		UserID: userID,
		Limit:  limit,
		Offset: offset,
	})
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to retrieve notes")
		return
	}

	for _, note := range notes {
		if userID != note.OwnerID {
			respondError(w, http.StatusForbidden, "Forbidden")
			return
		}
	}

	respondJSON(w, http.StatusOK, notes)
}

// Handler for returning the currently scoped (included to the request's context by a middleware)
// full note object.
func (rs *notesResource) GetFullNote(w http.ResponseWriter, r *http.Request) {
	fullNote, ok := r.Context().Value(noteCtxKey{}).(*data.GetFullNoteRow)
	if !ok {
		respondError(w, http.StatusNotFound, "Note not found")
		return
	}

	respondJSON(w, http.StatusOK, fullNote)
}

// Handler for hard deelting the currently scoped note (including its versions via database cascade).
func (rs *notesResource) Delete(w http.ResponseWriter, r *http.Request) {
	fullNote, ok := r.Context().Value(noteCtxKey{}).(*data.GetFullNoteRow)
	if !ok {
		respondError(w, http.StatusNotFound, "Note not found")
		return
	}

	user, ok := r.Context().Value(userCtxKey{}).(*userClaims)
	if !ok {
		respondError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	userID, err := uuid.Parse(user.Subject)
	if err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid user ID")
		return
	}

	err = rs.Notes.DeleteNote(r.Context(), data.DeleteNoteParams{
		ID:     fullNote.NoteID,
		UserID: userID, // NOTE: using `fullNote.userID` here'd be insecure
	})
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to delete note")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// Handler for listing the currently scoped note's version history. If pagination parameters
// (`limit` and `offset`) aren't defined, limit of 50 versions (with offset 0) will be returned.
func (rs *notesResource) GetVersionHistory(w http.ResponseWriter, r *http.Request) {
	fullNote, ok := r.Context().Value(noteCtxKey{}).(*data.GetFullNoteRow)
	if !ok {
		respondError(w, http.StatusNotFound, "Note not found")
		return
	}

	limit, offset := getPaginationParams(r)
	versions, err := rs.Notes.GetVersionHistory(r.Context(), data.GetVersionHistoryParams{
		NoteID: fullNote.NoteID,
		Limit:  limit,
		Offset: offset,
	})
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to get version history")
		return
	}

	respondJSON(w, http.StatusOK, versions)
}

// Handler for creating a new content version for the currently scoped note. Will check the incoming
// JSON object's integrity and perform a de-duplication check for identical versions stored in the
// database (SHA-1 hash of version contents). If a duplicate version is found, it'll be placed as the
// active version by swapping its version number to HEAD+1.
func (rs *notesResource) CreateVersion(w http.ResponseWriter, r *http.Request) {
	fullNote, ok := r.Context().Value(noteCtxKey{}).(*data.GetFullNoteRow)
	if !ok {
		respondError(w, http.StatusNotFound, "Note not found")
		return
	}

	var req struct {
		Title   *string `json:"title"`
		Content *string `json:"content"`
	}

	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Title == nil || req.Content == nil {
		respondError(w, http.StatusBadRequest, "Invalid request body")
		return
	}

	// Extra check for frontend readability reasons (max. length isn't specifically limited in the database)
	if len(*req.Title) > titleMaxLength {
		respondError(w, http.StatusBadRequest, fmt.Sprintf("Title must be shorter than %d characters", titleMaxLength))
		return
	}

	/*
		The SQL query handles de-duplication checks and "intelligent" versioning increments, so we
		don't have to worry about them here (`latest_version` = highest version number that exists
		in this note's context; `current_version` = note's active content version):

			- New version's contents are a duplicate of a historical version:
				- Don't increment `latest_version`
				- Sync `current_version` with the `version_number` of the duplicate version
			- New version's contents are unique:
				- Increment `latest_version`
				- Sync `current_version` with `latest_version`
	*/

	err := rs.Notes.CreateNoteVersion(r.Context(), data.CreateNoteVersionParams{
		NoteID:      fullNote.NoteID,
		Title:       *req.Title,
		Content:     *req.Content,
		ContentHash: sha1ContentHash(*req.Title, *req.Content),
	})
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to create note version")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// Handler for returning full data of the currently scoped note version. Identical to the beginning
// of the `RollbackNoteVersion` handler.
func (rs *notesResource) GetFullVersion(w http.ResponseWriter, r *http.Request) {
	fullVersion, ok := r.Context().Value(noteCtxKey{}).(*data.GetVersionRow)
	if !ok {
		respondError(w, http.StatusNotFound, "Note not found")
		return
	}

	respondJSON(w, http.StatusOK, fullVersion)
}