package briefing

import (
	"fmt"
	"reflect"
	"strings"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/facts"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/module"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
)

type ModuleContext struct {
	Identity  PreparedIdentity
	Resolved  report.Resolved
	Collected facts.CollectedFacts
	Derived   facts.DerivedFacts
	Units     string
	Timezone  string
	Location  *LocationContext
}

type ModuleBuilder func(ModuleContext, any) (*module.Output, error)

type ModulePromptExporter func(value any) (any, error)

type ModuleDefinition struct {
	ID                module.ID
	StanzaName        string
	DefaultOptions    any
	RequiredCollected []*factRequirement
	RequiredDerived   []*factRequirement
	SupportedReports  []report.ID
	MissingData       module.MissingDataBehavior
	AllowDuplicate    bool
	Builder           ModuleBuilder
	PromptExporter    ModulePromptExporter
}

type ModuleRegistry struct {
	definitions map[module.ID]ModuleDefinition
}

func unexpectedPromptExportValue(got any, want any) error {
	return fmt.Errorf("value has type %T, want %T", got, want)
}

func DefaultModuleRegistry() (ModuleRegistry, error) {
	return NewModuleRegistry(defaultModuleDefinitions())
}

func MustDefaultModuleRegistry() ModuleRegistry {
	registry, err := DefaultModuleRegistry()
	if err != nil {
		panic(err)
	}
	return registry
}

func NewModuleRegistry(definitions []ModuleDefinition) (ModuleRegistry, error) {
	registry := ModuleRegistry{definitions: map[module.ID]ModuleDefinition{}}
	seenStanzas := map[string]module.ID{}
	for i, definition := range definitions {
		if definition.ID == "" {
			return ModuleRegistry{}, fmt.Errorf("module definition[%d].id is required", i)
		}
		if definition.StanzaName == "" {
			return ModuleRegistry{}, fmt.Errorf("module %q stanza name is required", definition.ID)
		}
		if _, ok := registry.definitions[definition.ID]; ok {
			return ModuleRegistry{}, fmt.Errorf("duplicate module definition %q", definition.ID)
		}
		if definition.Builder == nil {
			return ModuleRegistry{}, fmt.Errorf("module %q has no builder", definition.ID)
		}
		if definition.MissingData == module.MissingDataWarn {
			return ModuleRegistry{}, fmt.Errorf("module %q uses unsupported missing data behavior %q", definition.ID, definition.MissingData)
		}
		if err := validateFactRequirements(definition); err != nil {
			return ModuleRegistry{}, err
		}
		if existingID, ok := seenStanzas[definition.StanzaName]; ok {
			return ModuleRegistry{}, fmt.Errorf("duplicate stanza name %q for modules %q and %q", definition.StanzaName, existingID, definition.ID)
		}
		seenStanzas[definition.StanzaName] = definition.ID
		registry.definitions[definition.ID] = definition
	}
	return registry, nil
}

func (r ModuleRegistry) Lookup(id module.ID) (ModuleDefinition, error) {
	definition, ok := r.definitions[id]
	if !ok {
		return ModuleDefinition{}, fmt.Errorf("unknown module %q", id)
	}
	return definition, nil
}

func (r ModuleRegistry) BuildModule(ctx ModuleContext, item module.ConfigItem) (*module.Output, error) {
	definition, err := r.Lookup(item.ID)
	if err != nil {
		return nil, err
	}
	if !definition.SupportsReport(ctx.Resolved.Definition.ID) {
		return nil, fmt.Errorf("module %q is not compatible with report %q", item.ID, ctx.Resolved.Definition.ID)
	}
	options, err := definition.CanonicalOptions(item.Options)
	if err != nil {
		return nil, err
	}
	if definition.Builder == nil {
		return nil, fmt.Errorf("module %q has no builder", item.ID)
	}
	missing := missingRequirements(definition, ctx)
	if len(missing) > 0 {
		switch definition.MissingData {
		case module.MissingDataOmit:
			return nil, nil
		case module.MissingDataError:
			return nil, fmt.Errorf("module %q missing required facts: %s", item.ID, strings.Join(missing, ", "))
		case module.MissingDataEmpty:
		case module.MissingDataWarn:
			return nil, fmt.Errorf("module %q uses unsupported missing data behavior %q", item.ID, definition.MissingData)
		default:
			return nil, fmt.Errorf("module %q has unknown missing data behavior %q", item.ID, definition.MissingData)
		}
	}
	if options == nil {
		options = definition.DefaultOptions
	}
	output, err := definition.Builder(ctx, options)
	if err != nil {
		return nil, err
	}
	if output == nil {
		return nil, nil
	}
	if output.ID != definition.ID {
		return nil, fmt.Errorf("module %q produced output id %q", definition.ID, output.ID)
	}
	if output.StanzaName != definition.StanzaName {
		return nil, fmt.Errorf("module %q produced stanza %q, want %q", definition.ID, output.StanzaName, definition.StanzaName)
	}
	if definition.PromptExporter == nil {
		output.PromptValue = output.Value
		return output, nil
	}
	promptValue, err := definition.PromptExporter(output.Value)
	if err != nil {
		return nil, fmt.Errorf("module %q stanza %q prompt export: %w", definition.ID, definition.StanzaName, err)
	}
	output.PromptValue = promptValue
	return output, nil
}

func missingRequirements(definition ModuleDefinition, ctx ModuleContext) []string {
	var missing []string
	for _, requirement := range definition.RequiredCollected {
		if !requirement.available(ctx) {
			missing = append(missing, requirement.String())
		}
	}
	for _, requirement := range definition.RequiredDerived {
		if !requirement.available(ctx) {
			missing = append(missing, requirement.String())
		}
	}
	return missing
}

func validateFactRequirements(definition ModuleDefinition) error {
	if err := validateFactRequirementCategory(definition.ID, definition.RequiredCollected, collectedFactRequirement); err != nil {
		return err
	}
	return validateFactRequirementCategory(definition.ID, definition.RequiredDerived, derivedFactRequirement)
}

func validateFactRequirementCategory(moduleID module.ID, requirements []*factRequirement, want factRequirementCategory) error {
	for _, requirement := range requirements {
		if requirement == nil {
			return fmt.Errorf("module %q uses unknown %s fact requirement %q", moduleID, want, "")
		}
		descriptor, ok := lookupFactRequirement(requirement.identity)
		if !ok || descriptor != requirement {
			return fmt.Errorf("module %q uses unknown %s fact requirement %q", moduleID, want, requirement.identity)
		}
		if descriptor.category != want {
			return fmt.Errorf("module %q lists %s fact requirement %q as %s", moduleID, descriptor.category, descriptor.identity, want)
		}
	}
	return nil
}

func lookupFactRequirement(identity string) (*factRequirement, bool) {
	for _, requirement := range factRequirementVocabulary {
		if requirement.identity == identity {
			return requirement, true
		}
	}
	return nil, false
}

func (r ModuleRegistry) ValidateComposition(reportID report.ID, items []module.ConfigItem) error {
	seenModules := map[module.ID]struct{}{}
	seenStanzas := map[string]module.ID{}
	for i, item := range items {
		definition, err := r.Lookup(item.ID)
		if err != nil {
			return fmt.Errorf("modules[%d]: %w", i, err)
		}
		if _, ok := seenModules[item.ID]; ok && !definition.AllowDuplicate {
			return fmt.Errorf("modules[%d]: duplicate module %q", i, item.ID)
		}
		seenModules[item.ID] = struct{}{}
		if existingID, ok := seenStanzas[definition.StanzaName]; ok {
			return fmt.Errorf("modules[%d]: duplicate stanza name %q for modules %q and %q", i, definition.StanzaName, existingID, item.ID)
		}
		seenStanzas[definition.StanzaName] = item.ID
		if !definition.SupportsReport(reportID) {
			return fmt.Errorf("modules[%d]: module %q is not compatible with report %q", i, item.ID, reportID)
		}
		if err := definition.ValidateOptions(item.Options); err != nil {
			return fmt.Errorf("modules[%d]: %w", i, err)
		}
	}
	return nil
}

func (d ModuleDefinition) SupportsReport(id report.ID) bool {
	if len(d.SupportedReports) == 0 {
		return true
	}
	for _, supported := range d.SupportedReports {
		if supported == id {
			return true
		}
	}
	return false
}

func (d ModuleDefinition) ValidateOptions(options any) error {
	if options == nil {
		return nil
	}
	if d.DefaultOptions == nil {
		return fmt.Errorf("module %q does not accept options", d.ID)
	}
	want := reflect.TypeOf(d.DefaultOptions)
	got := reflect.TypeOf(options)
	if got == want {
		return nil
	}
	if got.Kind() == reflect.Pointer && got.Elem() == want {
		return nil
	}
	return fmt.Errorf("module %q options have type %s, want %s", d.ID, got, want)
}

// CanonicalOptions validates options and converts an accepted typed pointer to its value form.
func (d ModuleDefinition) CanonicalOptions(options any) (any, error) {
	if err := d.ValidateOptions(options); err != nil {
		return nil, err
	}
	if options == nil {
		return nil, nil
	}
	value := reflect.ValueOf(options)
	if value.Kind() != reflect.Pointer {
		return options, nil
	}
	if value.IsNil() {
		return nil, fmt.Errorf("module %q options must not be a nil pointer", d.ID)
	}
	return value.Elem().Interface(), nil
}

func defaultModuleDefinitions() []ModuleDefinition {
	allReports := []report.ID{report.Daily, report.Today, report.Tomorrow, report.Hourly}
	daypartReports := []report.ID{report.Daily, report.Today, report.Tomorrow}
	return []ModuleDefinition{
		{
			ID:                module.Metadata,
			StanzaName:        "metadata",
			DefaultOptions:    module.MetadataOptions{},
			RequiredCollected: []*factRequirement{sourceMetadataRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataEmpty,
			Builder:           buildMetadataModule,
		},
		{
			ID:                module.CurrentConditions,
			StanzaName:        "current_conditions",
			DefaultOptions:    module.CurrentConditionsOptions{},
			RequiredCollected: []*factRequirement{currentConditionsRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataOmit,
			Builder:           buildCurrentConditionsModule,
			PromptExporter:    exportCurrentConditionsPromptValue,
		},
		{
			ID:                module.NarrativeForecast,
			StanzaName:        "narrative_forecast",
			DefaultOptions:    module.NarrativeForecastOptions{},
			RequiredCollected: []*factRequirement{narrativeForecastRequirement},
			RequiredDerived:   []*factRequirement{narrativePeriodsRequirement},
			SupportedReports:  []report.ID{report.Daily, report.Today, report.Tomorrow},
			MissingData:       module.MissingDataOmit,
			Builder:           buildNarrativeForecastModule,
		},
		{
			ID:                module.HourlyForecast,
			StanzaName:        "hourly_forecast",
			DefaultOptions:    module.HourlyForecastOptions{},
			RequiredCollected: []*factRequirement{hourlyForecastRequirement},
			RequiredDerived:   []*factRequirement{hourlyPeriodsRequirement},
			SupportedReports:  []report.ID{report.Daily, report.Today, report.Tomorrow, report.Hourly},
			MissingData:       module.MissingDataOmit,
			Builder:           buildHourlyForecastModule,
			PromptExporter:    exportHourlyForecastPromptValue,
		},
		{
			ID:               module.DerivedDailySummary,
			StanzaName:       "derived_daily_summary",
			DefaultOptions:   module.DerivedDailySummaryOptions{},
			RequiredDerived:  []*factRequirement{dailySummariesRequirement, precipTimingRequirement},
			SupportedReports: []report.ID{report.Daily, report.Today, report.Tomorrow},
			MissingData:      module.MissingDataError,
			Builder:          buildDerivedDailySummaryModule,
		},
		{
			ID:               module.DerivedDaypartSummaries,
			StanzaName:       "derived_daypart_summaries",
			DefaultOptions:   module.DerivedDaypartSummariesOptions{},
			RequiredDerived:  []*factRequirement{daypartSummariesRequirement},
			SupportedReports: daypartReports,
			MissingData:      module.MissingDataError,
			Builder:          buildDerivedDaypartSummariesModule,
			PromptExporter:   exportDerivedDaypartSummariesPromptValue,
		},
		{
			ID:               module.PrecipTiming,
			StanzaName:       "precip_timing",
			DefaultOptions:   module.PrecipTimingOptions{},
			RequiredDerived:  []*factRequirement{precipTimingRequirement},
			SupportedReports: allReports,
			MissingData:      module.MissingDataEmpty,
			Builder:          buildPrecipTimingModule,
		},
		{
			ID:                module.AlertDigest,
			StanzaName:        "alert_digest",
			DefaultOptions:    module.AlertDigestOptions{},
			RequiredCollected: []*factRequirement{alertsRequirement},
			RequiredDerived:   []*factRequirement{alertOverlapsRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataEmpty,
			Builder:           buildAlertDigestModule,
		},
		{
			ID:                module.SPCConvectiveOutlooks,
			StanzaName:        string(module.SPCConvectiveOutlooks),
			DefaultOptions:    module.SPCConvectiveOutlooksOptions{},
			RequiredCollected: []*factRequirement{spcOutlooksRequirement},
			RequiredDerived:   []*factRequirement{spcDerivedOutlooksRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataEmpty,
			Builder:           buildSPCConvectiveOutlooksModule,
		},
		{
			ID:                module.AreaForecastDiscussion,
			StanzaName:        "area_forecast_discussion",
			DefaultOptions:    module.AreaForecastDiscussionOptions{},
			RequiredCollected: []*factRequirement{discussionRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataOmit,
			Builder:           buildAreaForecastDiscussionModule,
		},
		{
			ID:                module.SPCConvectiveDiscussion,
			StanzaName:        string(module.SPCConvectiveDiscussion),
			DefaultOptions:    module.SPCConvectiveDiscussionOptions{},
			RequiredCollected: []*factRequirement{spcOutlooksRequirement},
			RequiredDerived:   []*factRequirement{spcDerivedOutlooksRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataOmit,
			Builder:           buildSPCConvectiveDiscussionModule,
		},
		{
			ID:                module.WeatherStory,
			StanzaName:        "weather_story",
			DefaultOptions:    module.WeatherStoryOptions{},
			RequiredCollected: []*factRequirement{weatherStoryRequirement},
			SupportedReports:  allReports,
			MissingData:       module.MissingDataOmit,
			Builder:           buildWeatherStoryModule,
		},
		{
			ID:               module.OutdoorWindows,
			StanzaName:       "outdoor_windows",
			DefaultOptions:   module.OutdoorWindowsOptions{},
			RequiredDerived:  []*factRequirement{daypartSummariesRequirement},
			SupportedReports: daypartReports,
			MissingData:      module.MissingDataEmpty,
			Builder:          buildOutdoorWindowsModule,
		},
		{
			ID:               module.TodayPlanning,
			StanzaName:       "today_planning",
			DefaultOptions:   module.TodayPlanningOptions{},
			RequiredDerived:  []*factRequirement{dailySummariesRequirement},
			SupportedReports: []report.ID{report.Today},
			MissingData:      module.MissingDataEmpty,
			Builder:          buildTodayPlanningModule,
		},
		{
			ID:               module.TomorrowPlanning,
			StanzaName:       "tomorrow_planning",
			DefaultOptions:   module.TomorrowPlanningOptions{},
			RequiredDerived:  []*factRequirement{dailySummariesRequirement},
			SupportedReports: []report.ID{report.Tomorrow},
			MissingData:      module.MissingDataEmpty,
			Builder:          buildTomorrowPlanningModule,
		},
		{
			ID:               module.DailyPlanning,
			StanzaName:       "daily_planning",
			DefaultOptions:   module.DailyPlanningOptions{},
			RequiredDerived:  []*factRequirement{dailySummariesRequirement},
			SupportedReports: []report.ID{report.Daily},
			MissingData:      module.MissingDataEmpty,
			Builder:          buildDailyPlanningModule,
		},
	}
}