package cli

import (
	"bytes"
	"net"
	"os"
	"runtime"
	"slices"
	"strconv"
	"sync"
	"time"

	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"

	"github.com/Control-D-Inc/ctrld"
)

// processStartTime is the time this process started. A reader compares it with
// the time of the header line to tell a restart from a rotation.
var processStartTime = time.Now()

const (
	// logHeaderMessage is the message of the header line. Log tools select the
	// header by this message.
	logHeaderMessage = "Log header"

	// interceptModeOff is the mode word for a ctrld that does not intercept.
	interceptModeOff = "off"

	// logHeaderTriggerSend marks the header that a log request renders. It
	// tells a reader that the line came from an upload, not from a file open.
	logHeaderTriggerSend = "send"

	// upstreamTypeUnspecified names an upstream that has no type in the config.
	// ctrld resolves the type at start, so the header must not claim one.
	upstreamTypeUnspecified = "unspecified"
)

// headerOSVersion reads the OS version once. The read starts a subprocess on
// macOS, and a header refresh follows every network change.
var headerOSVersion = sync.OnceValue(osVersion)

// logHeaderInput holds every value of a header line. The caller collects the
// values, so the renderer stays free of locks and of system calls.
type logHeaderInput struct {
	Version       string
	Commit        string
	OS            string
	Arch          string
	PID           int
	StartTime     time.Time
	InterceptMode string
	Listeners     []string
	UpstreamCount int
	UpstreamTypes []string
	ResolverUID   string
	LogFiles      []string
	Network       networkSnapshot
	Trigger       string
}

// renderLogHeader renders the header as one log line. A file writer stores the
// bytes and writes them itself, so the header reaches a file that the logger
// never fills.
func renderLogHeader(in logHeaderInput) []byte {
	var buf bytes.Buffer
	// The console sits above info on a default start, and a log file must hold
	// its header at every level, so the header takes a core of its own. The
	// line is JSON like the journal, because log tools read its fields.
	logger := &ctrld.Logger{Logger: zap.New(zapcore.NewCore(newJournalEncoder(), zapcore.AddSync(&buf), zapcore.DebugLevel))}
	event := journal(logger.Info()).
		Str("version", in.Version).
		Str("commit", in.Commit).
		Str("os", in.OS).
		Str("arch", in.Arch).
		Int("pid", in.PID).
		Str("start_time", in.StartTime.Format(time.RFC3339)).
		Str("intercept_mode", in.InterceptMode).
		Strs("listeners", in.Listeners).
		Int("upstream_count", in.UpstreamCount).
		Strs("upstream_types", in.UpstreamTypes).
		Str("resolver_uid", in.ResolverUID).
		Strs("log_files", in.LogFiles).
		Dict("network", snapshotDict(in.Network))
	if in.Trigger != "" {
		event = event.Str("trigger", in.Trigger)
	}
	event.Msg(logHeaderMessage)

	// The header is the first line of every file and of every upload, and it
	// bypasses the writers, so it passes the journal redaction here.
	return redactRetainedLine(buf.Bytes())
}

// logHeaderInput collects every header value of the running program.
func (p *prog) logHeaderInput() logHeaderInput {
	return p.logHeaderInputWith(p.networkSnapshot())
}

// logHeaderInputWith collects every header value around one network snapshot.
func (p *prog) logHeaderInputWith(network networkSnapshot) logHeaderInput {
	in := logHeaderInput{
		Version:   curVersion(),
		Commit:    commit,
		OS:        headerOSVersion(),
		Arch:      runtime.GOARCH,
		PID:       os.Getpid(),
		StartTime: processStartTime,
		// The resolver UID is a secret that the provisioning code strips from
		// every artifact, so the header keeps its first characters only.
		ResolverUID: redactToken(cdUID),
		LogFiles:    p.logHeaderFiles(),
		Network:     network,
	}
	p.headerConfigInto(&in)
	return in
}

// headerConfigInto reads the config under p.mu, because a reload replaces the
// config under that lock while log view and log send render a header.
func (p *prog) headerConfigInto(in *logHeaderInput) {
	p.mu.Lock()
	defer p.mu.Unlock()
	logHeaderFromConfig(p.cfg, in)
}

// sendLogHeader renders the header that leads one upload. The stored state can
// be older than the request, and support reads this line to learn the network
// of the moment the user asked.
func (p *prog) sendLogHeader() []byte {
	in := p.logHeaderInputWith(buildNetworkSnapshot(p.freshSnapshotInputs()))
	in.Trigger = logHeaderTriggerSend
	return renderLogHeader(in)
}

// logHeaderFiles names the files that this run writes, debug first.
func (p *prog) logHeaderFiles() []string {
	files := make([]string, 0, 3)
	for _, rf := range p.openLogFiles() {
		files = append(files, rf.currentPath())
	}
	return files
}

// refreshLogHeader renders the header and hands the bytes to every open file.
// The caller must hold no writer lock, because the render reads the config
// and the network.
func (p *prog) refreshLogHeader() {
	header := renderLogHeader(p.logHeaderInput())
	for _, rf := range p.openLogFiles() {
		rf.setHeader(header)
	}
}

// writeLogHeaders puts the header at the append point of each open file. A
// header that cannot land leaves the file usable, so the error only earns a
// warning.
func (p *prog) writeLogHeaders() {
	for _, rf := range p.openLogFiles() {
		if err := rf.writeHeader(); err != nil {
			mainLog.Load().Warn().Err(err).Msg("Could not write log header")
		}
	}
}

// logHeaderFromConfig fills the header fields that the config holds. It keeps
// every upstream endpoint, name, and bootstrap IP out of them, because a token
// can hide in each of them.
func logHeaderFromConfig(cfg *ctrld.Config, in *logHeaderInput) {
	if cfg == nil {
		in.InterceptMode = interceptModeOff
		return
	}
	in.InterceptMode = headerInterceptMode(cfg)
	in.Listeners = listenerAddresses(cfg)
	in.UpstreamCount = len(cfg.Upstream)
	in.UpstreamTypes = upstreamTypeWords(cfg)
}

// headerInterceptMode names the mode for the header. An unset mode means that
// ctrld does not intercept, which reads as off.
func headerInterceptMode(cfg *ctrld.Config) string {
	if mode := listenerInterceptMode(cfg); mode != "" {
		return mode
	}
	return interceptModeOff
}

func listenerAddresses(cfg *ctrld.Config) []string {
	addresses := make([]string, 0, len(cfg.Listener))
	for _, listener := range cfg.Listener {
		if listener == nil {
			continue
		}
		addresses = append(addresses, net.JoinHostPort(listener.IP, strconv.Itoa(listener.Port)))
	}
	slices.Sort(addresses)
	return addresses
}

func upstreamTypeWords(cfg *ctrld.Config) []string {
	words := make([]string, 0, len(cfg.Upstream))
	for _, upstream := range cfg.Upstream {
		if upstream == nil {
			continue
		}
		word := upstream.Type
		if word == "" {
			word = upstreamTypeUnspecified
		}
		if !slices.Contains(words, word) {
			words = append(words, word)
		}
	}
	slices.Sort(words)
	return words
}