// Package app owns application orchestration and top-level use cases.
package app

import (
	"context"
	"fmt"
	"path/filepath"
	"time"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/adapters/weatherapi"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/briefing"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/config"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
)

type ReportKind string

const (
	ReportDaily    ReportKind = "daily"
	ReportTomorrow ReportKind = "tomorrow"
	ReportThreeDay ReportKind = "three-day"
	ReportWeekend  ReportKind = "weekend"
	ReportStorm    ReportKind = "storm"
)

type BatchKind string

const (
	BatchMorning BatchKind = "morning"
	BatchEvening BatchKind = "evening"
)

type GenerateRequest struct {
	Config     config.Config
	Report     ReportKind
	OutputPath string
	Date       time.Time
	StormStart time.Time
	StormEnd   time.Time
}

type BatchRequest struct {
	Config config.Config
	Batch  BatchKind
}

type FetchBundleRequest struct {
	Config     config.Config
	OutputPath string
}

type DailyBriefingRequest struct {
	Config     config.Config
	Resolved   report.Resolved
	OutputPath string
}

type DailyBriefingResult struct {
	Package    briefing.Package
	OutputPath string
}

func Generate(ctx context.Context, req GenerateRequest) error {
	resolved, err := ResolveGenerate(req, time.Now())
	if err != nil {
		return err
	}
	if resolved.Definition.ID == report.DailyToday {
		_, err := GenerateDailyBriefing(ctx, DailyBriefingRequest{
			Config:     req.Config,
			Resolved:   resolved,
			OutputPath: req.OutputPath,
		})
		return err
	}
	return fmt.Errorf("generate is not implemented")
}

func RunBatch(ctx context.Context, req BatchRequest) error {
	_ = ctx
	if _, err := ResolveBatch(req, time.Now()); err != nil {
		return err
	}
	return fmt.Errorf("run is not implemented")
}

func ResolveGenerate(req GenerateRequest, now time.Time) (report.Resolved, error) {
	location, err := timeutil.LoadLocation(req.Config.WeatherAPI.Timezone)
	if err != nil {
		return report.Resolved{}, err
	}
	id, err := reportIDForCommand(req.Report)
	if err != nil {
		return report.Resolved{}, err
	}
	return report.DefaultRegistry().Resolve(id, report.ResolveRequest{
		Now:        now,
		Location:   location,
		Date:       req.Date,
		StormStart: req.StormStart,
		StormEnd:   req.StormEnd,
	})
}

func ResolveBatch(req BatchRequest, now time.Time) ([]report.Resolved, error) {
	location, err := timeutil.LoadLocation(req.Config.WeatherAPI.Timezone)
	if err != nil {
		return nil, err
	}
	batch, err := reportBatchForCommand(req.Batch)
	if err != nil {
		return nil, err
	}
	return report.DefaultRegistry().BatchReports(batch, report.ResolveRequest{
		Now:      now,
		Location: location,
	})
}

func reportIDForCommand(kind ReportKind) (report.ID, error) {
	switch kind {
	case ReportDaily:
		return report.DailyToday, nil
	case ReportTomorrow:
		return report.DailyTomorrow, nil
	case ReportThreeDay:
		return report.ThreeDay, nil
	case ReportWeekend:
		return report.Weekend, nil
	case ReportStorm:
		return report.Storm, nil
	default:
		return "", fmt.Errorf("unknown report command %q", kind)
	}
}

func reportBatchForCommand(kind BatchKind) (report.Batch, error) {
	switch kind {
	case BatchMorning:
		return report.Morning, nil
	case BatchEvening:
		return report.Evening, nil
	default:
		return "", fmt.Errorf("unknown batch command %q", kind)
	}
}

func FetchBundle(ctx context.Context, req FetchBundleRequest) (*forecast.Bundle, error) {
	client, err := weatherapi.New(req.Config)
	if err != nil {
		return nil, err
	}
	bundle, err := client.FetchBundle(ctx)
	if err != nil {
		return nil, err
	}
	return bundle, nil
}

func FetchAndSaveBundle(ctx context.Context, req FetchBundleRequest) (*forecast.Bundle, error) {
	if req.OutputPath == "" {
		return nil, fmt.Errorf("output path is required")
	}
	bundle, err := FetchBundle(ctx, req)
	if err != nil {
		return nil, err
	}
	if err := weatherapi.SaveBundle(req.OutputPath, bundle); err != nil {
		return nil, err
	}
	return bundle, nil
}

func GenerateDailyBriefing(ctx context.Context, req DailyBriefingRequest) (*DailyBriefingResult, error) {
	bundle, err := FetchBundle(ctx, FetchBundleRequest{Config: req.Config})
	if err != nil {
		return nil, err
	}
	pkg, err := BuildDailyBriefing(req, bundle)
	if err != nil {
		return nil, err
	}
	outputPath := req.OutputPath
	if outputPath == "" {
		outputPath = defaultBriefingPath(req.Config, req.Resolved)
	}
	if err := briefing.Save(outputPath, pkg); err != nil {
		return nil, err
	}
	return &DailyBriefingResult{Package: pkg, OutputPath: outputPath}, nil
}

func BuildDailyBriefing(req DailyBriefingRequest, bundle *forecast.Bundle) (briefing.Package, error) {
	location, err := timeutil.LoadLocation(req.Config.WeatherAPI.Timezone)
	if err != nil {
		return briefing.Package{}, err
	}
	dayparts := make([]forecast.DaypartDefinition, 0, len(req.Config.Dayparts))
	for _, daypart := range req.Config.Dayparts {
		dayparts = append(dayparts, forecast.DaypartDefinition{
			Name:  daypart.Name,
			Start: daypart.Start,
			End:   daypart.End,
		})
	}
	summary, err := forecast.BuildDailySummary(bundle, req.Resolved.ValidPeriod.Start, location, dayparts)
	if err != nil {
		return briefing.Package{}, err
	}
	return briefing.BuildDaily(briefing.BuildContext{
		Resolved: req.Resolved,
		Bundle:   bundle,
		Units:    req.Config.WeatherAPI.Units,
		Timezone: req.Config.WeatherAPI.Timezone,
	}, summary)
}

func defaultBriefingPath(cfg config.Config, resolved report.Resolved) string {
	validDate := resolved.ValidPeriod.Start.Format("2006-01-02")
	filename := validDate + "." + string(resolved.Definition.ID) + ".briefing.json"
	return filepath.Join(cfg.Workspace.Root, cfg.Workspace.SnapshotsDir, "daily", validDate, filename)
}