// Package loglist manages a list of logs to monitor.  The list of logs is based
// on Google's signed list.  Logs can also be added and removed manually.
package loglist

import (
	"context"
	"fmt"
	"time"

	"gitlab.torproject.org/rgdd/ct/pkg/metadata"
	"rgdd.se/silent-ct/internal/ioutil"
)

type Config struct {
	PermitBootstrap  bool   // Get and create initial log metadata if nothing valid is available on disk
	MetadataFile     string // Path to a dynamically updated metadata file that can be read/written
	HistoryDirectory string // Existing directory to store the history of downloaded metadata

	// Optional
	MetadataInFuture  time.Duration     // How wrong the metadata timestamp is allowed to be wrt. future dating
	MetadataGetsStale time.Duration     // How long until the metadata is considered stale
	MetadataIsRecent  time.Duration     // How long the metadata is considered recent
	HTTPTimeout       time.Duration     // Timeout when fetching metadata
	StaticLogs        []metadata.Log    // Takes precedence over the dynamically downloaded metadata
	RemoveLogs        []metadata.LogKey // Logs in the downloaded metadata with these keys are ignored
}

type LogList struct {
	cfg    Config
	md     metadata.Metadata
	source metadata.Loader
}

func New(cfg Config) (LogList, error) {
	if cfg.MetadataInFuture == 0 {
		cfg.MetadataInFuture = 24 * time.Hour
	}
	if cfg.MetadataGetsStale == 0 {
		cfg.MetadataGetsStale = 30 * 24 * time.Hour
	}
	if cfg.MetadataIsRecent == 0 {
		cfg.MetadataIsRecent = 1 * time.Hour
	}
	if cfg.HTTPTimeout == 0 {
		cfg.HTTPTimeout = 10 * time.Second
	}

	for i, log := range cfg.StaticLogs {
		if err := checkLog(log); err != nil {
			return LogList{}, fmt.Errorf("static logs: index %d: %v", i, err)
		}
	}
	for i, key := range cfg.RemoveLogs {
		if _, err := key.ID(); err != nil {
			return LogList{}, fmt.Errorf("remove logs: index %d: %v", i, err)
		}
	}

	s := metadata.NewHTTPSource(metadata.HTTPSourceOptions{Name: "google"})
	ll := LogList{cfg: cfg, source: &s}
	if err := ioutil.DirectoriesExist([]string{cfg.HistoryDirectory}); err != nil {
		return LogList{}, err
	}
	if err := ioutil.ReadJSON(cfg.MetadataFile, &ll.md); err != nil {
		if !ll.cfg.PermitBootstrap {
			return LogList{}, err
		}
		if _, _, err := ll.Update(context.Background()); err != nil {
			return LogList{}, err
		}
	}
	return ll, nil
}

func (ll *LogList) IsRecent() bool {
	return time.Now().Before(ll.md.CreatedAt.Add(ll.cfg.MetadataIsRecent))
}

func (ll *LogList) IsStale() bool {
	return time.Now().After(ll.md.CreatedAt.Add(ll.cfg.MetadataGetsStale))
}

func (ll *LogList) Generate() []metadata.Log {
	var configure []metadata.Log

	for _, log := range ll.cfg.StaticLogs {
		configure = append(configure, log)
	}
	for _, operator := range ll.md.Operators {
		for _, log := range operator.Logs {
			if findKey(ll.cfg.RemoveLogs, log) {
				continue // static configuration says to remove this log
			}
			if findLog(configure, log) {
				continue // static configuration takes precedence
			}
			if skipLog(log) {
				continue // not in a state where it makes sense to monitor
			}
			configure = append(configure, log)
		}
	}

	return configure
}

func (ll *LogList) Update(ctx context.Context) (added []metadata.Log, removed []metadata.Log, err error) {
	b, md, err := ll.archiveDynamic(ctx)
	if err != nil {
		return
	}
	if err = ioutil.CommitData(ll.cfg.MetadataFile, b); err != nil {
		return
	}

	added, removed = metadataLogDiff(ll.md, md)
	ll.md = md
	return
}

func (ll *LogList) archiveDynamic(ctx context.Context) ([]byte, metadata.Metadata, error) {
	llctx, cancel := context.WithTimeout(ctx, ll.cfg.HTTPTimeout)
	defer cancel()

	msg, sig, md, err := ll.source.Load(llctx)
	if err != nil {
		return nil, metadata.Metadata{}, err
	}
	if future := time.Now().Add(ll.cfg.MetadataInFuture); md.CreatedAt.After(future) {
		return nil, metadata.Metadata{}, fmt.Errorf("list created at %v is in the future", md.CreatedAt)
	}
	if md.CreatedAt.Before(ll.md.CreatedAt) {
		return nil, metadata.Metadata{}, fmt.Errorf("list created at %v is older than the current list", md.CreatedAt)
	}

	// FIXME: consider only archiving on major version bumps
	path := fmt.Sprintf("%s/%s.json", ll.cfg.HistoryDirectory, time.Now().Format("2006-01-02_1504"))
	if err := ioutil.CommitData(path, msg); err != nil {
		return nil, metadata.Metadata{}, err
	}
	if err := ioutil.CommitData(path+".sig", sig); err != nil {
		return nil, metadata.Metadata{}, err
	}
	return msg, md, nil
}