package server

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
	"unicode/utf8"

	"github.com/cdnutter/canon/internal/importer"
	"github.com/cdnutter/canon/internal/store"
)

const maxImportBytes = 2 << 20

// apiImportParse reads an uploaded CSV/TXT file, or pasted text, into rows.
func (s *Server) apiImportParse(w http.ResponseWriter, r *http.Request) {
	r.Body = http.MaxBytesReader(w, r.Body, maxImportBytes+64<<10)
	var data []byte
	name := "pasted.txt"
	if strings.HasPrefix(r.Header.Get("Content-Type"), "multipart/") {
		f, hdr, err := r.FormFile("file")
		if err != nil {
			s.writeErr(w, store.ValidationError{Msg: "Choose a .csv or .txt file (up to 2 MB)."})
			return
		}
		defer f.Close()
		if data, err = io.ReadAll(f); err != nil {
			s.writeErr(w, store.ValidationError{Msg: "That file is too big (2 MB at most)."})
			return
		}
		name = hdr.Filename
	} else {
		var in struct {
			Text string `json:"text"`
		}
		if err := decodeJSON(r, &in); err != nil {
			s.writeErr(w, err)
			return
		}
		data = []byte(in.Text)
	}
	rows, err := importer.Parse(data, name)
	if err != nil {
		if errors.Is(err, importer.ErrEmpty) {
			err = store.ValidationError{Msg: "No titles found. Use one title per line, or a CSV with a Title column."}
		} else {
			err = store.ValidationError{Msg: err.Error()}
		}
		s.writeErr(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"rows": rows, "max": importer.MaxRows})
}

type importMatch struct {
	Status  string         `json:"status"`
	Results []searchResult `json:"results"`
}

// apiImportMatch searches for one imported row and says how sure the best
// result is.
func (s *Server) apiImportMatch(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	listID, err := pathID(r)
	if err != nil {
		s.writeErr(w, err)
		return
	}
	var row importer.Row
	if err := decodeJSON(r, &row); err != nil {
		s.writeErr(w, err)
		return
	}
	row.Title = strings.TrimSpace(row.Title)
	if row.Title == "" || utf8.RuneCountInString(row.Title) > 300 {
		writeError(w, http.StatusBadRequest, "Each entry needs a title.")
		return
	}
	list, err := s.store.ListByID(ctx, listID)
	if err != nil {
		s.writeErr(w, err)
		return
	}
	p, err := s.providers.For(ctx, list.Category)
	if err != nil {
		s.writeErr(w, err)
		return
	}
	sctx, cancel := context.WithTimeout(ctx, 20*time.Second)
	defer cancel()
	results, err := p.Search(sctx, importer.Query(row, list.Category))
	if err != nil {
		s.log.Warn("import search failed", "provider", p.Name(), "err", err)
		writeError(w, http.StatusBadGateway, fmt.Sprintf("%s search failed: %v", p.Label(), err))
		return
	}
	status, scored := importer.Rank(row, list.Category, results)
	out := importMatch{Status: status, Results: []searchResult{}}
	for _, sc := range scored[:min(len(scored), 6)] {
		sr := searchResult{Result: sc.Result}
		if sc.Provider == "deezer" && hasPreviews(list.Category) {
			sr.PreviewRef = sc.ProviderID
		}
		if it, err := s.store.FindItemByProvider(ctx, listID, sc.Provider, sc.ProviderID); err == nil {
			sr.ExistingRank = it.Rank
		}
		out.Results = append(out.Results, sr)
	}
	writeJSON(w, http.StatusOK, out)
}