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

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

	"gitea.maximumdirect.net/eric/weatherreporter/internal/adapters/scriptorium"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/adapters/weatherapi"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/briefing"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/changes"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/config"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/promptinput"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/state"
	"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
	Now        time.Time
	Date       time.Time
	StormStart time.Time
	StormEnd   time.Time
}

type BatchRequest struct {
	Config    config.Config
	Batch     BatchKind
	Now       time.Time
	OutputDir string
	Renderer  Renderer
	Store     state.Store
}

type FetchBundleRequest struct {
	Config     config.Config
	OutputPath string
}

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

type DailyBriefingRequest = BriefingRequest

type ReportRequest struct {
	Config     config.Config
	Resolved   report.Resolved
	OutputPath string
	Renderer   Renderer
	Store      state.Store
}

type DailyReportRequest = ReportRequest

type BriefingResult struct {
	Package    briefing.Package
	OutputPath string
}

type DailyBriefingResult = BriefingResult

type ReportResult struct {
	Briefing        briefing.Package
	BriefingPath    string
	DataPackage     promptinput.Package
	DataPackagePath string
	PreflightPath   string
	ReportPath      string
	OutputPath      string
	Metadata        state.Metadata
	MetadataPath    string
	PriorSnapshot   *state.PriorSnapshot
	RecentChanges   []changes.Change
	RenderResult    *scriptorium.RenderResult
	RunResult       *scriptorium.RunResult
}

type DailyReportResult = ReportResult

type BatchResult struct {
	Batch      BatchKind           `json:"batch"`
	StartedAt  time.Time           `json:"startedAt"`
	FinishedAt time.Time           `json:"finishedAt"`
	Total      int                 `json:"total"`
	Succeeded  int                 `json:"succeeded"`
	Failed     int                 `json:"failed"`
	Reports    []BatchReportResult `json:"reports"`
}

type BatchReportResult struct {
	ReportID        report.ID       `json:"reportId"`
	ReportName      string          `json:"reportName"`
	PromptID        string          `json:"promptId"`
	RunID           string          `json:"runId"`
	Status          string          `json:"status"`
	Error           string          `json:"error,omitempty"`
	GeneratedAt     time.Time       `json:"generatedAt"`
	ValidPeriod     timeutil.Period `json:"validPeriod"`
	BriefingPath    string          `json:"briefingPath,omitempty"`
	DataPackagePath string          `json:"dataPackagePath,omitempty"`
	PreflightPath   string          `json:"preflightPath,omitempty"`
	ReportPath      string          `json:"reportPath,omitempty"`
	OutputPath      string          `json:"outputPath,omitempty"`
	MetadataPath    string          `json:"metadataPath,omitempty"`
}

type BatchError struct {
	Result *BatchResult
}

func (e BatchError) Error() string {
	if e.Result == nil {
		return "batch failed"
	}
	return fmt.Sprintf("batch %s failed: %d of %d reports failed", e.Result.Batch, e.Result.Failed, e.Result.Total)
}

type Renderer interface {
	Render(context.Context, scriptorium.RenderRequest) (*scriptorium.RenderResult, error)
	Run(context.Context, scriptorium.RunRequest) (*scriptorium.RunResult, error)
}

func Generate(ctx context.Context, req GenerateRequest) error {
	now := req.Now
	if now.IsZero() {
		now = time.Now()
	}
	resolved, err := ResolveGenerate(req, now)
	if err != nil {
		return err
	}
	if isGeneratedReport(resolved.Definition.ID) {
		_, err := GenerateReport(ctx, ReportRequest{
			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 {
	result, err := RunBatchDetailed(ctx, req)
	if err != nil {
		return err
	}
	if result.Failed > 0 {
		return BatchError{Result: result}
	}
	return nil
}

func RunBatchDetailed(ctx context.Context, req BatchRequest) (*BatchResult, error) {
	now := req.Now
	if now.IsZero() {
		now = time.Now()
	}
	resolvedReports, err := ResolveBatch(req, now)
	if err != nil {
		return nil, err
	}
	if req.Batch == BatchEvening || req.Batch == BatchMorning {
		store := req.Store
		if store == nil {
			defaultStore, err := defaultStore(req.Config)
			if err != nil {
				return nil, err
			}
			store = defaultStore
		}
		startedAt := now
		result := &BatchResult{Batch: req.Batch, StartedAt: startedAt}
		for _, resolved := range resolvedReports {
			if !isGeneratedReport(resolved.Definition.ID) {
				return nil, fmt.Errorf("run is not implemented")
			}
		}
		for _, resolved := range resolvedReports {
			item := batchReportResult(resolved)
			if paths, err := store.Paths(resolved); err == nil {
				item.BriefingPath = paths.Briefing
				item.DataPackagePath = paths.DataPackage
				item.PreflightPath = paths.Preflight
				item.ReportPath = paths.RenderedReport
				item.MetadataPath = paths.Metadata
			}
			outputPath := batchOutputPath(req.OutputDir, resolved.Definition)
			reportResult, err := GenerateReport(ctx, ReportRequest{
				Config:     req.Config,
				Resolved:   resolved,
				OutputPath: outputPath,
				Renderer:   req.Renderer,
				Store:      store,
			})
			if err != nil {
				item.Status = "failed"
				item.Error = err.Error()
				result.Failed++
			} else {
				item.Status = "succeeded"
				item.BriefingPath = reportResult.BriefingPath
				item.DataPackagePath = reportResult.DataPackagePath
				item.PreflightPath = reportResult.PreflightPath
				item.ReportPath = reportResult.ReportPath
				item.OutputPath = reportResult.OutputPath
				item.MetadataPath = reportResult.MetadataPath
				result.Succeeded++
			}
			result.Reports = append(result.Reports, item)
		}
		result.Total = len(result.Reports)
		result.FinishedAt = time.Now()
		return result, nil
	}
	return nil, fmt.Errorf("run is not implemented")
}

func batchReportResult(resolved report.Resolved) BatchReportResult {
	metadata := resolved.Metadata()
	return BatchReportResult{
		ReportID:    resolved.Definition.ID,
		ReportName:  resolved.Definition.Name,
		PromptID:    resolved.Definition.PromptID,
		RunID:       metadata.RunID,
		GeneratedAt: metadata.GeneratedAt,
		ValidPeriod: metadata.ValidPeriod,
	}
}

func batchOutputPath(outputDir string, definition report.Definition) string {
	if outputDir == "" || definition.DefaultOutputName == "" {
		return ""
	}
	name := strings.ReplaceAll(definition.DefaultOutputName, "_", "-")
	return filepath.Join(outputDir, name)
}

func isGeneratedReport(id report.ID) bool {
	return isDailyReport(id) || id == report.ThreeDay || id == report.Weekend || id == report.Storm
}

func isDailyReport(id report.ID) bool {
	return id == report.DailyToday || id == report.DailyTomorrow
}

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) {
	return GenerateBriefing(ctx, req)
}

func GenerateBriefing(ctx context.Context, req BriefingRequest) (*BriefingResult, error) {
	bundle, err := FetchBundle(ctx, FetchBundleRequest{Config: req.Config})
	if err != nil {
		return nil, err
	}
	pkg, err := BuildBriefing(req, bundle)
	if err != nil {
		return nil, err
	}
	outputPath := req.OutputPath
	if outputPath == "" {
		store, err := defaultStore(req.Config)
		if err != nil {
			return nil, err
		}
		paths, err := store.Paths(req.Resolved)
		if err != nil {
			return nil, err
		}
		outputPath = paths.Briefing
	}
	if err := briefing.Save(outputPath, pkg); err != nil {
		return nil, err
	}
	return &BriefingResult{Package: pkg, OutputPath: outputPath}, nil
}

func GenerateDailyReport(ctx context.Context, req DailyReportRequest) (*DailyReportResult, error) {
	return GenerateReport(ctx, req)
}

func GenerateReport(ctx context.Context, req ReportRequest) (*ReportResult, error) {
	store := req.Store
	if store == nil {
		defaultStore, err := defaultStore(req.Config)
		if err != nil {
			return nil, err
		}
		store = defaultStore
	}
	paths, err := store.Paths(req.Resolved)
	if err != nil {
		return nil, err
	}
	priorSnapshot, err := store.FindPriorSnapshot(ctx, req.Resolved)
	if err != nil {
		return nil, err
	}

	bundle, err := FetchBundle(ctx, FetchBundleRequest{Config: req.Config})
	if err != nil {
		return nil, err
	}
	briefingPackage, err := BuildBriefing(BriefingRequest{
		Config:   req.Config,
		Resolved: req.Resolved,
	}, bundle)
	if err != nil {
		return nil, err
	}

	briefingPath, err := store.SaveBriefing(ctx, req.Resolved, briefingPackage)
	if err != nil {
		return nil, err
	}

	recentChanges, err := recentChanges(ctx, store, priorSnapshot, briefingPackage, req.Config.RecentChange)
	if err != nil {
		return nil, err
	}
	dataPackage, err := promptinput.BuildWithRecentChanges(briefingPackage, recentChanges)
	if err != nil {
		return nil, err
	}
	dataPackagePath, err := store.SaveDataPackage(ctx, req.Resolved, dataPackage)
	if err != nil {
		return nil, err
	}

	renderer := req.Renderer
	if renderer == nil {
		renderer = scriptorium.Runner{
			Binary:     req.Config.Scriptorium.Binary,
			ConfigPath: req.Config.Scriptorium.ConfigPath,
			Profile:    req.Config.Scriptorium.Profile,
			Timeout:    req.Config.Scriptorium.Timeout,
			ExtraArgs:  req.Config.Scriptorium.ExtraArgs,
		}
	}
	renderResult, renderErr := renderer.Render(ctx, scriptorium.RenderRequest{
		PromptID:        req.Resolved.Definition.PromptID,
		DataPackagePath: dataPackagePath,
	})

	preflightPath := paths.Preflight
	if renderResult != nil {
		var err error
		preflightPath, err = store.SavePreflight(ctx, req.Resolved, renderResult)
		if err != nil {
			return nil, err
		}
	}
	metadata := state.BuildMetadata(req.Resolved, briefingPackage, state.ArtifactPaths{
		Briefing:       briefingPath,
		Metadata:       paths.Metadata,
		DataPackage:    dataPackagePath,
		Preflight:      preflightPath,
		RenderedReport: paths.RenderedReport,
	})
	metadataPath, metadataErr := store.SaveMetadata(ctx, metadata)
	if metadataErr != nil {
		return nil, metadataErr
	}
	if renderErr != nil {
		return nil, renderErr
	}

	reportPath, err := store.PrepareRenderedReport(ctx, req.Resolved)
	if err != nil {
		return nil, err
	}
	runResult, runErr := renderer.Run(ctx, scriptorium.RunRequest{
		PromptID:        req.Resolved.Definition.PromptID,
		DataPackagePath: dataPackagePath,
		OutputPath:      reportPath,
	})
	if runErr == nil && req.OutputPath != "" && req.OutputPath != reportPath {
		if err := copyFileAtomic(reportPath, req.OutputPath); err != nil {
			return nil, err
		}
	}
	outputPath := reportPath
	if req.OutputPath != "" {
		outputPath = req.OutputPath
	}
	metadata.RenderedReportPath = reportPath
	metadataPath, metadataErr = store.SaveMetadata(ctx, metadata)
	if metadataErr != nil {
		return nil, metadataErr
	}
	if runErr != nil {
		return nil, runErr
	}

	return &ReportResult{
		Briefing:        briefingPackage,
		BriefingPath:    briefingPath,
		DataPackage:     dataPackage,
		DataPackagePath: dataPackagePath,
		PreflightPath:   preflightPath,
		ReportPath:      reportPath,
		OutputPath:      outputPath,
		Metadata:        metadata,
		MetadataPath:    metadataPath,
		PriorSnapshot:   priorSnapshot,
		RecentChanges:   recentChanges,
		RenderResult:    renderResult,
		RunResult:       runResult,
	}, nil
}

func BuildDailyBriefing(req DailyBriefingRequest, bundle *forecast.Bundle) (briefing.Package, error) {
	return BuildBriefing(req, bundle)
}

func BuildBriefing(req BriefingRequest, 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,
		})
	}
	switch req.Resolved.Definition.ID {
	case report.DailyToday, report.DailyTomorrow:
		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)
	case report.ThreeDay, report.Weekend:
		summaries, err := forecast.BuildPeriodDailySummaries(bundle, req.Resolved.ValidPeriod, location, dayparts)
		if err != nil {
			return briefing.Package{}, err
		}
		if req.Resolved.Definition.ID == report.Weekend {
			return briefing.BuildWeekend(briefing.BuildContext{
				Resolved: req.Resolved,
				Bundle:   bundle,
				Units:    req.Config.WeatherAPI.Units,
				Timezone: req.Config.WeatherAPI.Timezone,
			}, summaries)
		}
		return briefing.BuildThreeDay(briefing.BuildContext{
			Resolved: req.Resolved,
			Bundle:   bundle,
			Units:    req.Config.WeatherAPI.Units,
			Timezone: req.Config.WeatherAPI.Timezone,
		}, summaries)
	case report.Storm:
		return briefing.BuildStorm(briefing.BuildContext{
			Resolved: req.Resolved,
			Bundle:   bundle,
			Units:    req.Config.WeatherAPI.Units,
			Timezone: req.Config.WeatherAPI.Timezone,
		})
	default:
		return briefing.Package{}, fmt.Errorf("briefing is not implemented for report %q", req.Resolved.Definition.ID)
	}
}

func defaultStore(cfg config.Config) (*state.FilesystemStore, error) {
	return state.NewFilesystemStore(cfg.Workspace)
}

func dailyRecentChanges(ctx context.Context, store state.Store, priorSnapshot *state.PriorSnapshot, current briefing.Package, cfg config.RecentChangeConfig) ([]changes.Change, error) {
	return recentChanges(ctx, store, priorSnapshot, current, cfg)
}

func recentChanges(ctx context.Context, store state.Store, priorSnapshot *state.PriorSnapshot, current briefing.Package, cfg config.RecentChangeConfig) ([]changes.Change, error) {
	if priorSnapshot == nil {
		return nil, nil
	}
	previous, err := store.LoadBriefing(ctx, priorSnapshot.BriefingPath)
	if err != nil {
		return nil, err
	}
	thresholds := changes.Thresholds{
		TemperatureDegrees:       cfg.TemperatureDegrees,
		PrecipProbabilityPoints:  cfg.PrecipProbabilityPoints,
		WindGustMilesPerHour:     cfg.WindGustMilesPerHour,
		PrecipTimingShiftMinutes: cfg.PrecipTimingShiftMinutes,
	}
	switch current.Metadata.ReportID {
	case report.DailyToday, report.DailyTomorrow:
		return changes.CompareDaily(previous, current, thresholds)
	case report.ThreeDay:
		return changes.CompareThreeDay(previous, current, thresholds)
	case report.Weekend:
		return changes.CompareWeekend(previous, current, thresholds)
	default:
		return nil, nil
	}
}

func copyFileAtomic(source string, target string) error {
	data, err := os.ReadFile(source)
	if err != nil {
		return fmt.Errorf("read rendered report %q: %w", source, err)
	}
	if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
		return fmt.Errorf("create report output directory %q: %w", filepath.Dir(target), err)
	}
	tmp, err := os.CreateTemp(filepath.Dir(target), "."+filepath.Base(target)+".*.tmp")
	if err != nil {
		return fmt.Errorf("create temporary report output file: %w", err)
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return fmt.Errorf("write temporary report output file: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("close temporary report output file: %w", err)
	}
	if err := os.Rename(tmpName, target); err != nil {
		return fmt.Errorf("save report output %q: %w", target, err)
	}
	return nil
}