package providers

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode"
)

// igdb searches the Internet Game Database, authenticating through Twitch.
type igdb struct {
	r      *Registry
	id     string
	secret string
}

type igdbTokens struct {
	mu      sync.Mutex
	credKey string
	token   string
	expires time.Time
}

func (g *igdb) Name() string  { return "igdb" }
func (g *igdb) Label() string { return "IGDB" }

func (g *igdb) token(ctx context.Context, fresh bool) (string, error) {
	c := g.r.igdb
	c.mu.Lock()
	defer c.mu.Unlock()
	credKey := g.id + "\x00" + g.secret
	if !fresh && c.credKey == credKey && c.token != "" && time.Now().Before(c.expires) {
		return c.token, nil
	}
	q := url.Values{"client_id": {g.id}, "client_secret": {g.secret}, "grant_type": {"client_credentials"}}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, "https://id.twitch.tv/oauth2/token?"+q.Encode(), nil)
	if err != nil {
		return "", err
	}
	var resp struct {
		AccessToken string `json:"access_token"`
		ExpiresIn   int64  `json:"expires_in"`
	}
	if err := g.r.do(req, &resp); err != nil {
		if isStatus(err, 400) || isStatus(err, 403) {
			return "", fmt.Errorf("Twitch rejected the IGDB client ID/secret; check them under Settings → Integrations")
		}
		return "", err
	}
	c.credKey, c.token = credKey, resp.AccessToken
	c.expires = time.Now().Add(time.Duration(resp.ExpiresIn)*time.Second - time.Hour)
	return c.token, nil
}

func (g *igdb) Search(ctx context.Context, query string) ([]Result, error) {
	q := strings.NewReplacer(`\`, ``, `"`, `\"`).Replace(query)
	body := `search "` + q + `";
fields name,first_release_date,cover.image_id,summary,url,involved_companies.developer,involved_companies.publisher,involved_companies.company.name,involved_companies.company.parent.name,involved_companies.company.parent.parent.name,involved_companies.company.parent.parent.parent.name,platforms.abbreviation,platforms.name;
limit 25;`
	var games []struct {
		ID               int64  `json:"id"`
		Name             string `json:"name"`
		FirstReleaseDate int64  `json:"first_release_date"`
		Summary          string `json:"summary"`
		URL              string `json:"url"`
		Cover            struct {
			ImageID string `json:"image_id"`
		} `json:"cover"`
		InvolvedCompanies []igdbInvolved `json:"involved_companies"`
		Platforms         []struct {
			Abbreviation string `json:"abbreviation"`
			Name         string `json:"name"`
		} `json:"platforms"`
	}
	for attempt := 0; ; attempt++ {
		tok, err := g.token(ctx, attempt > 0)
		if err != nil {
			return nil, err
		}
		req, err := http.NewRequestWithContext(ctx, http.MethodPost, "https://api.igdb.com/v4/games", strings.NewReader(body))
		if err != nil {
			return nil, err
		}
		req.Header.Set("Client-ID", g.id)
		req.Header.Set("Authorization", "Bearer "+tok)
		req.Header.Set("Content-Type", "text/plain")
		err = g.r.do(req, &games)
		if isStatus(err, 401) && attempt == 0 {
			continue
		}
		if err != nil {
			return nil, err
		}
		break
	}
	out := make([]Result, 0, len(games))
	for _, gm := range games {
		var plats []string
		for _, p := range gm.Platforms {
			name := p.Abbreviation
			if name == "" {
				name = p.Name
			}
			plats = append(plats, name)
		}
		r := Result{
			Provider:    "igdb",
			ProviderID:  strconv.FormatInt(gm.ID, 10),
			Title:       gm.Name,
			Subtitle:    strings.Join(igdbStudios(gm.InvolvedCompanies), ", "),
			ExternalURL: gm.URL,
			Overview:    truncate(gm.Summary, maxDescription),
			Extra:       map[string]string{},
		}
		if gm.FirstReleaseDate > 0 {
			r.Year = strconv.Itoa(time.Unix(gm.FirstReleaseDate, 0).UTC().Year())
		}
		if gm.Cover.ImageID != "" {
			r.ImageURL = "https://images.igdb.com/igdb/image/upload/t_cover_big_2x/" + gm.Cover.ImageID + ".jpg"
		}
		if len(plats) > 0 {
			r.Extra["platforms"] = strings.Join(plats, ", ")
		}
		out = append(out, r)
	}
	return out, nil
}

type igdbInvolved struct {
	Developer bool        `json:"developer"`
	Publisher bool        `json:"publisher"`
	Company   igdbCompany `json:"company"`
}

// igdbStudios names who made a game: its developers, or its publishers when
// IGDB lists no developer, with internal divisions credited to their company.
func igdbStudios(involved []igdbInvolved) []string {
	var devs, pubs []string
	for _, ic := range involved {
		if ic.Company.Name == "" {
			continue
		}
		if ic.Developer {
			devs = appendUnique(devs, studioName(&ic.Company))
		}
		if ic.Publisher {
			pubs = appendUnique(pubs, studioName(&ic.Company))
		}
	}
	if len(devs) == 0 {
		return pubs
	}
	return devs
}

// igdbCompany is a company with as much of its parent chain as was
// requested. IGDB sends an unexpanded parent as a bare ID, which is ignored.
type igdbCompany struct {
	Name   string
	Parent *igdbCompany
}

func (c *igdbCompany) UnmarshalJSON(b []byte) error {
	if len(b) == 0 || b[0] != '{' {
		return nil
	}
	var raw struct {
		Name   string       `json:"name"`
		Parent *igdbCompany `json:"parent"`
	}
	if err := json.Unmarshal(b, &raw); err != nil {
		return err
	}
	c.Name, c.Parent = raw.Name, raw.Parent
	if c.Parent != nil && c.Parent.Name == "" {
		c.Parent = nil
	}
	return nil
}

// studioName credits an internal division to the company it belongs to.
// IGDB lists the exact team, so Super Mario Sunshine's developer is
// "Nintendo EAD" and DK Bananza's is "Nintendo EPD Production Group No. 8".
// When a studio's name starts with the same word as its parent's, it's a
// division of that company and we show the parent ("Nintendo"). Studios
// with their own identity keep their name: Retro Studios (owned by
// Nintendo) or Naughty Dog (owned by Sony).
func studioName(c *igdbCompany) string {
	for c.Parent != nil && sameFirstWord(c.Name, c.Parent.Name) {
		c = c.Parent
	}
	return c.Name
}

func sameFirstWord(a, b string) bool {
	first := func(s string) string {
		f := strings.FieldsFunc(strings.ToLower(s), func(r rune) bool {
			return !unicode.IsLetter(r) && !unicode.IsDigit(r)
		})
		if len(f) == 0 {
			return ""
		}
		return f[0]
	}
	fa := first(a)
	return fa != "" && fa == first(b)
}

func appendUnique(list []string, s string) []string {
	for _, x := range list {
		if x == s {
			return list
		}
	}
	return append(list, s)
}