package main

import (
	"errors"
	"fmt"
	"math"
	"net/http"
	"regexp"
	"strconv"
	"strings"

	"github.com/go-chi/chi/v5"
)

var themeHexColorPattern = regexp.MustCompile(`^#[0-9a-fA-F]{6}$`)

var requiredThemeColors = []string{
	"background",
	"foreground",
	"primary",
	"primaryForeground",
	"muted",
	"mutedForeground",
	"border",
	"accent",
}

type authoringIdentity struct {
	UserID   string
	TenantID string
}

type themeValidationResult struct {
	Valid    bool     `json:"valid" bson:"valid"`
	Errors   []string `json:"errors" bson:"errors"`
	Warnings []string `json:"warnings" bson:"warnings"`
}

func (a *app) createAuthoringRun(w http.ResponseWriter, r *http.Request) {
	var payload struct {
		Brief map[string]any `json:"brief"`
	}
	if err := decodeJSON(r, &payload); err != nil || len(payload.Brief) == 0 {
		writeError(w, http.StatusBadRequest, "brief is required")
		return
	}
	run, err := a.startAuthoringRun(r, Doc(payload.Brief))
	if err != nil {
		writeAuthoringError(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, run)
}

func (a *app) getAuthoringRun(w http.ResponseWriter, r *http.Request) {
	run, err := a.getOwnedAuthoringRun(r, chi.URLParam(r, "id"))
	if err != nil {
		writeAuthoringError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, run)
}

func (a *app) proposeAuthoringThemeHTTP(w http.ResponseWriter, r *http.Request) {
	var payload struct {
		IdempotencyKey string         `json:"idempotencyKey"`
		Theme          map[string]any `json:"theme"`
	}
	if err := decodeJSON(r, &payload); err != nil || strings.TrimSpace(payload.IdempotencyKey) == "" || len(payload.Theme) == 0 {
		writeError(w, http.StatusBadRequest, "idempotencyKey and theme are required")
		return
	}
	run, err := a.proposeAuthoringTheme(r, chi.URLParam(r, "id"), strings.TrimSpace(payload.IdempotencyKey), Doc(payload.Theme))
	if err != nil {
		writeAuthoringError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, run)
}

func (a *app) validateAuthoringThemeHTTP(w http.ResponseWriter, r *http.Request) {
	result, err := a.validateAuthoringTheme(r, chi.URLParam(r, "id"))
	if err != nil {
		writeAuthoringError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, result)
}

func (a *app) deleteAuthoringRun(w http.ResponseWriter, r *http.Request) {
	result, err := a.discardAuthoringRun(r, chi.URLParam(r, "id"))
	if err != nil {
		writeAuthoringError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, result)
}

func writeAuthoringError(w http.ResponseWriter, err error) {
	switch err.Error() {
	case "authentication required":
		writeError(w, http.StatusUnauthorized, err.Error())
	case "tenant claim required":
		writeError(w, http.StatusForbidden, err.Error())
	case "authoring store unavailable":
		writeError(w, http.StatusServiceUnavailable, err.Error())
	case "authoring run not found":
		writeError(w, http.StatusNotFound, err.Error())
	default:
		writeError(w, http.StatusBadRequest, err.Error())
	}
}

func themeSchemaResource() map[string]any {
	properties := map[string]any{}
	for _, field := range requiredThemeColors {
		properties[field] = map[string]any{"type": "string", "pattern": `^#[0-9a-fA-F]{6}$`}
	}
	properties["radius"] = map[string]any{"type": "number", "minimum": 0, "maximum": 2}
	properties["fontFamily"] = map[string]any{"type": "string", "minLength": 1, "maxLength": 200}
	return map[string]any{
		"type":                 "object",
		"properties":           properties,
		"required":             append(requiredThemeColors, "radius", "fontFamily"),
		"additionalProperties": false,
		"constraints": map[string]any{
			"minimumTextContrast": 4.5,
			"arbitraryCSS":        false,
		},
	}
}

func (a *app) callExternalAuthoringTool(r *http.Request, name string, arguments map[string]any) (any, error) {
	switch name {
	case "authoring_start":
		brief, ok := asDocument(arguments["brief"])
		if !ok || len(brief) == 0 {
			return nil, errors.New("brief is required")
		}
		return a.startAuthoringRun(r, brief)
	case "authoring_get_status":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		return a.getOwnedAuthoringRun(r, runID)
	case "theme_propose":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		idempotencyKey, err := requiredArgumentString(arguments, "idempotencyKey")
		if err != nil {
			return nil, err
		}
		theme, ok := asDocument(arguments["theme"])
		if !ok {
			return nil, errors.New("theme is required")
		}
		return a.proposeAuthoringTheme(r, runID, idempotencyKey, theme)
	case "theme_validate":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		return a.validateAuthoringTheme(r, runID)
	case "site_propose_structure":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		idempotencyKey, err := requiredArgumentString(arguments, "idempotencyKey")
		if err != nil {
			return nil, err
		}
		site, ok := asDocument(arguments["site"])
		if !ok {
			return nil, errors.New("site is required")
		}
		return a.proposeAuthoringSiteStructure(r, runID, idempotencyKey, site)
	case "site_upsert_page_proposal":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		idempotencyKey, err := requiredArgumentString(arguments, "idempotencyKey")
		if err != nil {
			return nil, err
		}
		page, ok := asDocument(arguments["page"])
		if !ok {
			return nil, errors.New("page is required")
		}
		return a.upsertAuthoringSitePage(r, runID, idempotencyKey, page)
	case "site_validate":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		return a.validateAuthoringSite(r, runID)
	case "authoring_get_review_link":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		return a.authoringReviewLink(r, runID)
	case "authoring_discard":
		runID, err := requiredArgumentString(arguments, "runId")
		if err != nil {
			return nil, err
		}
		return a.discardAuthoringRun(r, runID)
	default:
		return nil, errors.New("unknown or unavailable tool")
	}
}

func (a *app) startAuthoringRun(r *http.Request, brief Doc) (Doc, error) {
	identity, err := a.resolveAuthoringIdentity(r)
	if err != nil {
		return nil, err
	}
	if a.db == nil {
		return nil, errors.New("authoring store unavailable")
	}
	return a.create("authoring_runs", Doc{
		"tenantId":        identity.TenantID,
		"userId":          identity.UserID,
		"status":          "draft",
		"brief":           brief,
		"proposal":        Doc{},
		"proposalRevision": 0,
		"validation":      Doc{},
		"idempotencyKeys": Doc{},
		"source":          "mcp",
	})
}

func (a *app) proposeAuthoringTheme(r *http.Request, runID, idempotencyKey string, theme Doc) (Doc, error) {
	run, identity, err := a.getMutableAuthoringRun(r, runID)
	if err != nil {
		return nil, err
	}

	keys, _ := asDocument(run["idempotencyKeys"])
	if keys != nil && anyToString(keys["theme_propose"]) == idempotencyKey {
		return run, nil
	}
	if keys == nil {
		keys = Doc{}
	}
	keys["theme_propose"] = idempotencyKey

	proposal, _ := asDocument(run["proposal"])
	if proposal == nil {
		proposal = Doc{}
	}
	proposal["theme"] = theme
	return a.updateAuthoringProposal(runID, identity, run, proposal, keys)
}

func (a *app) validateAuthoringTheme(r *http.Request, runID string) (Doc, error) {
	run, identity, err := a.getOwnedAuthoringRunWithIdentity(r, runID)
	if err != nil {
		return nil, err
	}
	proposal, _ := asDocument(run["proposal"])
	theme, ok := asDocument(proposal["theme"])
	if !ok {
		return nil, errors.New("theme proposal not found")
	}

	validation := validateThemeProposal(theme)
	validationDocument, _ := asDocument(run["validation"])
	if validationDocument == nil {
		validationDocument = Doc{}
	}
	validationDocument["theme"] = validation
	status := "proposed"
	if validation.Valid && allProposalValidationsPass(proposal, validationDocument) {
		status = "ready_for_review"
	}
	updated, err := a.patchWithUnsetScoped("authoring_runs", runID, Doc{
		"validation": validationDocument,
		"status":     status,
	}, nil, identity.TenantID, true)
	if err != nil {
		return nil, err
	}
	return Doc{
		"runId":              runID,
		"status":             status,
		"proposalRevision":   updated["proposalRevision"],
		"validation":         validation,
		"requiresCMSApproval": true,
	}, nil
}

func (a *app) authoringReviewLink(r *http.Request, runID string) (Doc, error) {
	run, _, err := a.getOwnedAuthoringRunWithIdentity(r, runID)
	if err != nil {
		return nil, err
	}
	if anyToString(run["status"]) != "ready_for_review" {
		return nil, errors.New("run must pass validation before review")
	}
	return Doc{
		"runId":    runID,
		"status":   "ready_for_review",
		"reviewUrl": a.cfg.AppBaseURL + "/admin/authoring/runs/" + runID,
	}, nil
}

func (a *app) discardAuthoringRun(r *http.Request, runID string) (Doc, error) {
	run, identity, err := a.getOwnedAuthoringRunWithIdentity(r, runID)
	if err != nil {
		return nil, err
	}
	if status := anyToString(run["status"]); status == "applied" || status == "published" {
		return nil, errors.New("applied runs cannot be discarded")
	}
	updated, err := a.patchWithUnsetScoped("authoring_runs", runID, Doc{"status": "cancelled"}, nil, identity.TenantID, true)
	if err != nil {
		return nil, err
	}
	return Doc{"runId": runID, "status": updated["status"]}, nil
}

func (a *app) getOwnedAuthoringRun(r *http.Request, runID string) (Doc, error) {
	run, _, err := a.getOwnedAuthoringRunWithIdentity(r, runID)
	return run, err
}

func (a *app) getOwnedAuthoringRunWithIdentity(r *http.Request, runID string) (Doc, authoringIdentity, error) {
	identity, err := a.resolveAuthoringIdentity(r)
	if err != nil {
		return nil, authoringIdentity{}, err
	}
	if a.db == nil {
		return nil, authoringIdentity{}, errors.New("authoring store unavailable")
	}
	run, err := a.getByIDScoped("authoring_runs", runID, identity.TenantID, true)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, authoringIdentity{}, errors.New("authoring run not found")
		}
		return nil, authoringIdentity{}, errors.New("failed to load authoring run")
	}
	if anyToString(run["userId"]) != identity.UserID && !a.isAuthoringAdmin(r) {
		return nil, authoringIdentity{}, errors.New("authoring run not found")
	}
	return run, identity, nil
}

func (a *app) resolveAuthoringIdentity(r *http.Request) (authoringIdentity, error) {
	if a.cfg.AuthDisabled {
		return authoringIdentity{UserID: "development-user", TenantID: "development"}, nil
	}
	claims, _ := r.Context().Value(userClaimsKey).(*accessClaims)
	tenant, _ := r.Context().Value(tenantContextKey).(tenantContext)
	userID := resolveClaimsUserID(claims)
	if userID == "" {
		return authoringIdentity{}, errors.New("authentication required")
	}
	if strings.TrimSpace(tenant.ID) == "" {
		return authoringIdentity{}, errors.New("tenant claim required")
	}
	return authoringIdentity{UserID: userID, TenantID: strings.TrimSpace(tenant.ID)}, nil
}

func (a *app) isAuthoringAdmin(r *http.Request) bool {
	claims, _ := r.Context().Value(userClaimsKey).(*accessClaims)
	return hasAnyRole(claims, "admin", "platform_owner", "platform_admin")
}

func validateThemeProposal(theme Doc) themeValidationResult {
	result := themeValidationResult{Valid: true, Errors: []string{}, Warnings: []string{}}
	for _, field := range requiredThemeColors {
		value := strings.TrimSpace(anyToString(theme[field]))
		if !themeHexColorPattern.MatchString(value) {
			result.Errors = append(result.Errors, field+" must be a six-digit hex color")
		}
	}
	fontFamily := strings.TrimSpace(anyToString(theme["fontFamily"]))
	if fontFamily == "" || len(fontFamily) > 200 {
		result.Errors = append(result.Errors, "fontFamily is required and must be at most 200 characters")
	}
	radius, ok := numericValue(theme["radius"])
	if !ok || radius < 0 || radius > 2 {
		result.Errors = append(result.Errors, "radius must be between 0 and 2")
	}
	if len(result.Errors) == 0 {
		for _, pair := range [][3]string{
			{"foreground", "background", "foreground/background"},
			{"primaryForeground", "primary", "primary foreground/primary"},
			{"mutedForeground", "muted", "muted foreground/muted"},
		} {
			ratio := contrastRatio(anyToString(theme[pair[0]]), anyToString(theme[pair[1]]))
			if ratio < 4.5 {
				result.Errors = append(result.Errors, fmt.Sprintf("%s contrast %.2f is below 4.5", pair[2], ratio))
			}
		}
	}
	result.Valid = len(result.Errors) == 0
	return result
}

func contrastRatio(first, second string) float64 {
	firstLuminance := relativeLuminance(first)
	secondLuminance := relativeLuminance(second)
	lighter := math.Max(firstLuminance, secondLuminance)
	darker := math.Min(firstLuminance, secondLuminance)
	return (lighter + 0.05) / (darker + 0.05)
}

func relativeLuminance(color string) float64 {
	if !themeHexColorPattern.MatchString(color) {
		return 0
	}
	channels := make([]float64, 0, 3)
	for index := 1; index < 7; index += 2 {
		value, _ := strconv.ParseInt(color[index:index+2], 16, 64)
		channel := float64(value) / 255
		if channel <= 0.04045 {
			channel /= 12.92
		} else {
			channel = math.Pow((channel+0.055)/1.055, 2.4)
		}
		channels = append(channels, channel)
	}
	return 0.2126*channels[0] + 0.7152*channels[1] + 0.0722*channels[2]
}

func requiredArgumentString(arguments map[string]any, key string) (string, error) {
	value := strings.TrimSpace(anyToString(arguments[key]))
	if value == "" {
		return "", fmt.Errorf("%s is required", key)
	}
	return value, nil
}

func asDocument(value any) (Doc, bool) {
	switch typed := value.(type) {
	case Doc:
		return typed, true
	case map[string]any:
		return Doc(typed), true
	default:
		return nil, false
	}
}

func int64Number(value any) int64 {
	number, _ := numericValue(value)
	return int64(number)
}

func numericValue(value any) (float64, bool) {
	switch typed := value.(type) {
	case int:
		return float64(typed), true
	case int32:
		return float64(typed), true
	case int64:
		return float64(typed), true
	case float32:
		return float64(typed), true
	case float64:
		return typed, true
	default:
		return 0, false
	}
}