// Package briefing builds report-specific structured briefing packages.
package briefing

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/report"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
)

const SchemaVersion = "weatherreporter.briefing.v1"

type Package struct {
	Metadata Metadata  `json:"metadata"`
	Daily    *Daily    `json:"daily,omitempty"`
	ThreeDay *ThreeDay `json:"threeDay,omitempty"`
	Weekend  *Weekend  `json:"weekend,omitempty"`
	Storm    *Storm    `json:"storm,omitempty"`
}

type Metadata struct {
	SchemaVersion    string                   `json:"schemaVersion"`
	RunID            string                   `json:"runId"`
	ReportID         report.ID                `json:"reportId"`
	Variant          string                   `json:"variant,omitempty"`
	PromptID         string                   `json:"promptId"`
	GeneratedAt      time.Time                `json:"generatedAt"`
	Units            string                   `json:"units"`
	Timezone         string                   `json:"timezone"`
	ValidPeriod      timeutil.Period          `json:"validPeriod"`
	SourceLocationID string                   `json:"sourceLocationId,omitempty"`
	SourceLocation   string                   `json:"sourceLocation,omitempty"`
	Sources          []SourceMetadata         `json:"sources,omitempty"`
	SourceWarnings   []forecast.SourceWarning `json:"sourceWarnings,omitempty"`
}

type SourceMetadata struct {
	Name       string                   `json:"name"`
	Endpoint   string                   `json:"endpoint,omitempty"`
	FetchedAt  time.Time                `json:"fetchedAt"`
	IssuedAt   *time.Time               `json:"issuedAt,omitempty"`
	UpdatedAt  *time.Time               `json:"updatedAt,omitempty"`
	DataSHA256 string                   `json:"dataSha256,omitempty"`
	Missing    bool                     `json:"missing,omitempty"`
	Warnings   []forecast.SourceWarning `json:"warnings,omitempty"`
}

type BuildContext struct {
	Resolved report.Resolved
	Bundle   *forecast.Bundle
	Units    string
	Timezone string
}

func BuildMetadata(ctx BuildContext) Metadata {
	metadata := ctx.Resolved.Metadata()
	sourceLocationID, sourceLocation := sourceLocation(ctx.Bundle)
	return Metadata{
		SchemaVersion:    SchemaVersion,
		RunID:            metadata.RunID,
		ReportID:         metadata.ReportID,
		Variant:          variantForReport(metadata.ReportID),
		PromptID:         metadata.PromptID,
		GeneratedAt:      metadata.GeneratedAt,
		Units:            ctx.Units,
		Timezone:         ctx.Timezone,
		ValidPeriod:      metadata.ValidPeriod,
		SourceLocationID: sourceLocationID,
		SourceLocation:   sourceLocation,
		Sources:          sourceMetadata(ctx.Bundle),
		SourceWarnings:   sourceWarnings(ctx.Bundle),
	}
}

func Save(path string, pkg Package) error {
	data, err := json.MarshalIndent(pkg, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal briefing package: %w", err)
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("create briefing directory %q: %w", filepath.Dir(path), err)
	}
	tmp, err := os.CreateTemp(filepath.Dir(path), "."+filepath.Base(path)+".*.tmp")
	if err != nil {
		return fmt.Errorf("create temporary briefing file: %w", err)
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)

	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return fmt.Errorf("write temporary briefing file: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("close temporary briefing file: %w", err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		return fmt.Errorf("save briefing %q: %w", path, err)
	}
	return nil
}

func sourceLocation(bundle *forecast.Bundle) (string, string) {
	if bundle == nil {
		return "", ""
	}
	for _, run := range []*forecast.ForecastRun{bundle.Hourly, bundle.Narrative, bundle.Daily} {
		if run == nil {
			continue
		}
		if run.LocationID != "" || run.LocationName != "" {
			return run.LocationID, run.LocationName
		}
	}
	return "", ""
}

func sourceMetadata(bundle *forecast.Bundle) []SourceMetadata {
	if bundle == nil {
		return nil
	}
	out := make([]SourceMetadata, 0, len(bundle.Sources))
	for _, source := range bundle.Sources {
		out = append(out, SourceMetadata{
			Name:       source.Name,
			Endpoint:   source.Endpoint,
			FetchedAt:  source.FetchedAt,
			IssuedAt:   source.IssuedAt,
			UpdatedAt:  source.UpdatedAt,
			DataSHA256: source.DataSHA256,
			Missing:    source.Missing,
			Warnings:   source.Warnings,
		})
	}
	return out
}

func sourceWarnings(bundle *forecast.Bundle) []forecast.SourceWarning {
	if bundle == nil {
		return nil
	}
	return bundle.Warnings
}

func variantForReport(id report.ID) string {
	switch id {
	case report.DailyToday:
		return "today"
	case report.DailyTomorrow:
		return "tomorrow"
	default:
		return ""
	}
}