package api

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"net/url"
	"slices"
	"strings"

	"git.golem15.com/golem15/sm-journal-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/phrasebook"
	"git.golem15.com/golem15/summercms/modules/wire"
	"gorm.io/gorm"
)

// permManageSettings guards the settings and maintenance routes.
const permManageSettings = "golem15.journal.manage_settings"

// requireManageSettings answers 403 {"error":"Insufficient permissions"}
// without golem15.journal.manage_settings.
func requireManageSettings(w http.ResponseWriter, pr *bouncer.Principal) bool {
	if !cabana.Allows(pr, []string{permManageSettings}) {
		writeAPIError(w, http.StatusForbidden, errInsufficientPerms)
		return false
	}
	return true
}

// serializeSettings is the settings answer: every fillable column by name.
func serializeSettings(s models.Settings) map[string]any {
	return map[string]any{
		"show_all_posts":        s.ShowAllPosts,
		"use_rich_editor":       s.UseRichEditor,
		"search_use_typesense":  s.SearchUseTypesense,
		"search_title_weight":   s.SearchTitleWeight,
		"search_excerpt_weight": s.SearchExcerptWeight,
		"search_content_weight": s.SearchContentWeight,
		"rss_enabled":           s.RSSEnabled,
		"rss_include_content":   s.RSSIncludeContent,
		"rss_title":             s.RSSTitle,
		"rss_description":       s.RSSDescription,
		"rss_language":          s.RSSLanguage,
		"rss_copyright":         s.RSSCopyright,
		"rss_image_url":         s.RSSImageURL,
		"rss_posts_per_feed":    s.RSSPostsPerFeed,
		"content_h1_to_h2":      s.ContentH1ToH2,
		"generic_anchors":       s.GenericAnchors,
	}
}

// loadSettings reads the settings row (ID 1); without one it is the
// migration's defaults, not yet stored.
func loadSettings(db *gorm.DB) (models.Settings, error) {
	var s models.Settings
	err := db.First(&s, 1).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return models.Settings{
			ID: 1, ShowAllPosts: true, SearchTitleWeight: 5, SearchExcerptWeight: 3, SearchContentWeight: 1,
			RSSEnabled: true, RSSLanguage: "en-us", RSSPostsPerFeed: 20, ContentH1ToH2: true,
		}, nil
	}
	return s, err
}

// ShowSettings is GET /_journal/api/v1/settings: the Journal settings row,
// for golem15.journal.manage_settings (MCP journal_get_settings).
func ShowSettings(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		r, pr, ok := requireBackendPrincipal(app, w, r)
		if !ok || !requireManageSettings(w, pr) {
			return
		}
		db, err := gdb(app)
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		s, err := loadSettings(db.WithContext(r.Context()))
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		wire.WriteJSON(w, http.StatusOK, map[string]any{"data": serializeSettings(s)})
	}
}

// UpdateSettings is PUT /_journal/api/v1/settings: it writes the submitted
// fillable columns (models.Settings.Fillable) after checking them against
// the model's Rules, and answers the row. Other keys are ignored. Changing
// content_h1_to_h2 never rewrites stored content (D-50). MCP
// journal_update_settings.
func UpdateSettings(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		r, pr, ok := requireBackendPrincipal(app, w, r)
		if !ok || !requireManageSettings(w, pr) {
			return
		}
		db, err := gdb(app)
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		body, err := readJSONObject(r)
		if err != nil {
			writeAPIError(w, http.StatusBadRequest, errValidationFailed)
			return
		}
		fillable := models.Settings{}.Fillable()
		values := map[string]any{}
		for key, v := range body {
			if slices.Contains(fillable, key) {
				values[key] = plainJSON(v)
			}
		}
		var tr *phrasebook.Translator
		if app != nil {
			tr, _ = app.Lookup[*phrasebook.Translator]()
		}
		var saved models.Settings
		var verrs map[string][]string
		err = lagoon.Transaction(r.Context(), db, func(ctx context.Context, tx *gorm.DB) error {
			s, err := loadSettings(tx)
			if err != nil {
				return err
			}
			rules := map[string]string{}
			for key, rule := range s.Rules() {
				if _, has := values[key]; has {
					rules[key], verrs = settingsRule(key, rule, values[key], verrs)
				}
			}
			if len(verrs) > 0 {
				return nil
			}
			if verrs, err = lagoon.Validate(ctx, tx, &s, rules, values, tr); err != nil || len(verrs) > 0 {
				return err
			}
			if err := lagoon.Fill(&s, fillable, values, true); err != nil {
				var typeErr *lagoon.FillTypeError
				if errors.As(err, &typeErr) {
					verrs = map[string][]string{typeErr.Key: {"The " + typeErr.Key + " field is invalid."}}
					return nil
				}
				return err
			}
			s.ID = 1
			if err := tx.Save(&s).Error; err != nil {
				return err
			}
			saved = s
			return nil
		})
		if err != nil {
			pluginLog.ErrorContext(r.Context(), "journal api: settings update failed", "error", err)
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		if len(verrs) > 0 {
			writeValidation(w, verrs)
			return
		}
		wire.WriteJSON(w, http.StatusOK, map[string]any{"data": serializeSettings(saved)})
	}
}

// plainJSON turns a json.Number (readJSONObject decodes with UseNumber)
// into an int64, or a float64 when it is not an integer.
func plainJSON(v any) any {
	n, ok := v.(json.Number)
	if !ok {
		return v
	}
	if i, err := n.Int64(); err == nil {
		return i
	}
	if f, err := n.Float64(); err == nil {
		return f
	}
	return v
}

// settingsRule checks the string and url tokens of a Settings rule, which
// lagoon.Validate does not know, and returns the rule without them for
// lagoon.Validate. A failed check is added to verrs.
func settingsRule(key, rule string, value any, verrs map[string][]string) (string, map[string][]string) {
	var kept []string
	for _, tok := range strings.Split(rule, "|") {
		switch tok {
		case "string":
			if _, ok := value.(string); !ok && value != nil {
				verrs = addSettingsError(verrs, key, "The "+key+" must be a string.")
			}
		case "url":
			if text, _ := value.(string); text != "" {
				u, err := url.Parse(text)
				if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
					verrs = addSettingsError(verrs, key, "The "+key+" format is invalid.")
				}
			}
		default:
			kept = append(kept, tok)
		}
	}
	return strings.Join(kept, "|"), verrs
}

func addSettingsError(verrs map[string][]string, key, msg string) map[string][]string {
	if verrs == nil {
		verrs = map[string][]string{}
	}
	verrs[key] = append(verrs[key], msg)
	return verrs
}