package service

import (
	"database/sql"
	"encoding/json/v2"
	"errors"
	"log/slog"
	"net/http"
	"strings"
	"unicode/utf8"

	"code.chimeric.al/chimerical/odidere/internal/conversation"
	"code.chimeric.al/chimerical/odidere/internal/db"
)

func (svc *Service) listConversations(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	rows, err := svc.dbr.SelectConversationsUserId(ctx, "default")
	if err != nil {
		log.ErrorContext(
			ctx, "failed to list conversations",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.MarshalWrite(w, rows); err != nil {
		log.ErrorContext(
			ctx, "failed to encode conversations response",
			slog.Any("error", err),
		)
	}
}

func (svc *Service) createConversation(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
		req struct {
			Title         *string `json:"title"`
			SystemMessage *string `json:"system_message"`
		}
	)

	r.Body = http.MaxBytesReader(w, r.Body, 32<<20)
	if err := json.UnmarshalRead(r.Body, &req); err != nil {
		log.ErrorContext(
			ctx, "failed to decode request",
			slog.Any("error", err),
		)
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	system := svc.cfg.SystemMessage
	if req.SystemMessage != nil {
		system = *req.SystemMessage
	}
	saved, _, err := svc.newConversation(
		ctx, "default", req.Title, system,
	)
	if err != nil {
		log.ErrorContext(
			ctx, "failed to create conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	if err := json.MarshalWrite(w, saved); err != nil {
		log.ErrorContext(
			ctx, "failed to encode conversation response",
			slog.Any("error", err),
		)
	}
}

func (svc *Service) getConversationHandler(
	w http.ResponseWriter,
	r *http.Request,
) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	saved, err := svc.dbr.SelectConversationIdUserId(
		ctx, r.PathValue("id"), "default",
	)
	if errors.Is(err, sql.ErrNoRows) {
		http.NotFound(w, r)
		return
	}
	if err != nil {
		log.ErrorContext(
			ctx, "failed to load conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.MarshalWrite(w, saved); err != nil {
		log.ErrorContext(
			ctx, "failed to encode conversation response",
			slog.Any("error", err),
		)
	}
}

// updateConversation renames one conversation. The handler trims
// the title, then rejects an empty title or a title longer than
// conversation.MaxTitleLength with 400. A conversation that does
// not exist, or belongs to another user, returns 404. The rename
// is allowed while inference runs: a title is not a message, and a
// concurrent inference does not read or write it.
func (svc *Service) updateConversation(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
		id  = r.PathValue("id")
		req struct {
			Title string `json:"title"`
		}
	)

	r.Body = http.MaxBytesReader(w, r.Body, 32<<20)
	if err := json.UnmarshalRead(r.Body, &req); err != nil {
		log.ErrorContext(
			ctx, "failed to decode request",
			slog.Any("error", err),
		)
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	req.Title = strings.TrimSpace(req.Title)
	if req.Title == "" {
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}
	if utf8.RuneCountInString(req.Title) > conversation.MaxTitleLength {
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	// Load the conversation first, so a rename of a conversation
	// that does not belong to the user reports 404, not a silent
	// no-op.
	if _, err := svc.dbr.SelectConversationIdUserId(
		ctx, id, "default",
	); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.NotFound(w, r)
			return
		}
		log.ErrorContext(
			ctx, "failed to load conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	saved, err := svc.dbw.UpdateConversationTitle(
		ctx,
		db.UpdateConversationTitleParams{
			Id:    id,
			Title: req.Title,
		},
	)
	if err != nil {
		// The conversation was deleted after the load above.
		if errors.Is(err, sql.ErrNoRows) {
			http.NotFound(w, r)
			return
		}
		log.ErrorContext(
			ctx, "failed to rename conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.MarshalWrite(w, saved); err != nil {
		log.ErrorContext(
			ctx, "failed to encode conversation response",
			slog.Any("error", err),
		)
	}
}

func (svc *Service) deleteConversation(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
		id  = r.PathValue("id")
	)

	if _, err := svc.dbr.SelectConversationIdUserId(
		ctx, id, "default",
	); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.NotFound(w, r)
			return
		}
		log.ErrorContext(
			ctx, "failed to load conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}
	c, err := svc.getConversation(ctx, id)
	if errors.Is(err, sql.ErrNoRows) {
		http.NotFound(w, r)
		return
	}
	if err != nil {
		log.ErrorContext(
			ctx, "failed to get conversation handle",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}
	if err := c.Delete(ctx); err != nil {
		log.ErrorContext(
			ctx, "failed to delete conversation",
			slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
		return
	}

	svc.mu.Lock()
	delete(svc.conversations, id)
	svc.mu.Unlock()
	w.WriteHeader(http.StatusNoContent)
}