package subprocess

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"

	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
)

const (
	// MaxStdoutDiagnosticBytes bounds persisted stdout from one external command.
	MaxStdoutDiagnosticBytes int64 = 8 * 1024 * 1024
	// MaxStderrDiagnosticBytes bounds persisted stderr from one external command.
	MaxStderrDiagnosticBytes int64 = 8 * 1024 * 1024
)

var inheritedEnvironmentNames = map[string]struct{}{
	"COMSPEC":    {},
	"HOME":       {},
	"PATH":       {},
	"SYSTEMROOT": {},
	"TMP":        {},
	"TMPDIR":     {},
	"TEMP":       {},
	"WINDIR":     {},
	// These test-only helper destinations let the adapter package tests exercise
	// real command invocation without widening the production environment.
	"AUDITA_HELPER_RECORD_PATH":      {},
	"AUDITA_HELPER_MODE":             {},
	"GO_WANT_AUDITA_HELPER":          {},
	"GO_WANT_SCRIPTORIUM_HELPER":     {},
	"GO_WANT_SERIATIM_HELPER":        {},
	"GO_WANT_SUBPROCESS_HELPER":      {},
	"NOTARIUS_CAPTURE_DIR":           {},
	"NOTARIUS_RECEIPT_FIXTURE":       {},
	"SCRIPTORIUM_HELPER_RECORD_PATH": {},
	"SCRIPTORIUM_HELPER_MODE":        {},
	"SERIATIM_HELPER_RECORD_PATH":    {},
	"SERIATIM_HELPER_MODE":           {},
}

var sensitiveEnvironmentNames = map[string]struct{}{
	"ANTHROPIC_API_KEY":     {},
	"API_KEY":               {},
	"AUDITA_LLM_API_KEY":    {},
	"AWS_ACCESS_KEY_ID":     {},
	"AWS_SECRET_ACCESS_KEY": {},
	"AWS_SESSION_TOKEN":     {},
	"OPENAI_API_KEY":        {},
	"OPENROUTER_API_KEY":    {},
}

type captureLimitError struct {
	stream string
	owner  string
	limit  int64
}

func (e *captureLimitError) Error() string {
	return fmt.Sprintf("%s diagnostic capture for %s exceeded %d bytes", e.stream, e.owner, e.limit)
}

type logWriters struct {
	files  []*os.File
	Stdout io.Writer
	Stderr io.Writer

	limits chan *captureLimitError
	mu     sync.Mutex
	limit  *captureLimitError
	stdout *diagnosticWriter
	stderr *diagnosticWriter
}

type diagnosticWriter struct {
	logs      *logWriters
	stream    string
	owner     string
	target    io.Writer
	limit     int64
	received  int64
	persisted int64
	redactor  streamRedactor
}

func openLogWriters(stdoutPath, stderrPath, owner string, sensitiveValues []string) (*logWriters, error) {
	logs := &logWriters{limits: make(chan *captureLimitError, 1)}
	cleanStdout := cleanLogPath(stdoutPath)
	cleanStderr := cleanLogPath(stderrPath)

	stdoutFile, err := openDiagnosticFile(cleanStdout)
	if err != nil {
		return nil, fmt.Errorf("open stdout log: %w", err)
	}
	stderrFile := stdoutFile
	if cleanStdout != cleanStderr {
		stderrFile, err = openDiagnosticFile(cleanStderr)
		if err != nil {
			_ = stdoutFile.Close()
			return nil, fmt.Errorf("open stderr log: %w", err)
		}
	}
	if cleanStdout == cleanStderr {
		logs.files = []*os.File{stdoutFile}
	} else {
		logs.files = []*os.File{stdoutFile, stderrFile}
	}

	logs.stdout = newDiagnosticWriter(logs, "stdout", owner, stdoutFile, MaxStdoutDiagnosticBytes, sensitiveValues)
	logs.stderr = newDiagnosticWriter(logs, "stderr", owner, stderrFile, MaxStderrDiagnosticBytes, sensitiveValues)
	logs.Stdout = logs.stdout
	logs.Stderr = logs.stderr
	return logs, nil
}

func newDiagnosticWriter(logs *logWriters, stream, owner string, target io.Writer, limit int64, sensitiveValues []string) *diagnosticWriter {
	return &diagnosticWriter{
		logs:     logs,
		stream:   stream,
		owner:    owner,
		target:   target,
		limit:    limit,
		redactor: newStreamRedactor(sensitiveValues),
	}
}

func (w *diagnosticWriter) Write(data []byte) (int, error) {
	if w.received >= w.limit {
		return len(data), w.reachLimit()
	}
	accepted := data
	if remaining := w.limit - w.received; int64(len(accepted)) > remaining {
		accepted = accepted[:remaining]
	}
	w.received += int64(len(accepted))
	if err := w.writeRedacted(w.redactor.Write(accepted)); err != nil {
		return len(data), err
	}
	if len(accepted) != len(data) {
		return len(data), w.reachLimit()
	}
	return len(data), nil
}

func (w *diagnosticWriter) Flush() error {
	return w.writeRedacted(w.redactor.Flush())
}

func (w *diagnosticWriter) writeRedacted(data []byte) error {
	if len(data) == 0 {
		return nil
	}
	w.logs.mu.Lock()
	remaining := w.limit - w.persisted
	if remaining <= 0 {
		w.logs.mu.Unlock()
		return w.reachLimit()
	}
	toWrite := data
	exceeded := int64(len(data)) > remaining
	if exceeded {
		toWrite = toWrite[:remaining]
	}
	written, err := w.target.Write(toWrite)
	w.persisted += int64(written)
	w.logs.mu.Unlock()
	if err != nil {
		return err
	}
	if exceeded {
		return w.reachLimit()
	}
	return nil
}

func (w *diagnosticWriter) reachLimit() error {
	limit := &captureLimitError{stream: w.stream, owner: w.owner, limit: w.limit}
	w.logs.mu.Lock()
	if w.logs.limit == nil {
		w.logs.limit = limit
		w.logs.limits <- limit
	}
	w.logs.mu.Unlock()
	return limit
}

func (l *logWriters) Limits() <-chan *captureLimitError { return l.limits }

func (l *logWriters) Limit() *captureLimitError {
	l.mu.Lock()
	defer l.mu.Unlock()
	return l.limit
}

func (l *logWriters) Flush() error {
	return joinErrors(l.stdout.Flush(), l.stderr.Flush())
}

func (l *logWriters) Close() {
	_ = l.Flush()
	for _, file := range l.files {
		_ = file.Close()
	}
}

func cleanLogPath(path string) string {
	trimmed := strings.TrimSpace(path)
	if trimmed == "" {
		return ""
	}
	return filepath.Clean(trimmed)
}

func openDiagnosticFile(path string) (*os.File, error) {
	if path == "" {
		return os.OpenFile(os.DevNull, os.O_WRONLY, 0)
	}
	if err := fileops.EnsureWorkspaceDirectory(filepath.Dir(path)); err != nil {
		return nil, fmt.Errorf("create log directory for %q: %w", path, err)
	}
	file, err := os.Create(path)
	if err != nil {
		return nil, fmt.Errorf("open log file %q: %w", path, err)
	}
	if err := file.Chmod(fileops.WorkspaceFileMode); err != nil {
		_ = file.Close()
		return nil, fmt.Errorf("set log file permissions %q: %w", path, err)
	}
	return file, nil
}

func (r RunRequest) diagnosticOwner() string {
	if owner := strings.TrimSpace(r.DiagnosticOwner); owner != "" {
		return owner
	}
	return "subprocess"
}

func buildChildEnvironment(base []string, overrides map[string]string) []string {
	values := make(map[string]string, len(inheritedEnvironmentNames)+len(overrides))
	for _, item := range base {
		name, value, ok := strings.Cut(item, "=")
		if !ok {
			continue
		}
		normalized := strings.ToUpper(name)
		if _, allowed := inheritedEnvironmentNames[normalized]; allowed {
			values[name] = value
		}
	}
	for name, value := range overrides {
		values[name] = value
	}
	names := make([]string, 0, len(values))
	for name := range values {
		names = append(names, name)
	}
	sort.Strings(names)
	out := make([]string, 0, len(names))
	for _, name := range names {
		out = append(out, name+"="+values[name])
	}
	return out
}

func sensitiveEnvironmentValues(environment []string, additionalNames []string) []string {
	names := make(map[string]struct{}, len(sensitiveEnvironmentNames)+len(additionalNames))
	for name := range sensitiveEnvironmentNames {
		names[name] = struct{}{}
	}
	for _, name := range additionalNames {
		if trimmed := strings.ToUpper(strings.TrimSpace(name)); trimmed != "" {
			names[trimmed] = struct{}{}
		}
	}
	values := make([]string, 0, len(names))
	for _, item := range environment {
		name, value, ok := strings.Cut(item, "=")
		if !ok || strings.TrimSpace(value) == "" {
			continue
		}
		if _, sensitive := names[strings.ToUpper(name)]; sensitive {
			values = append(values, value)
		}
	}
	return values
}

type streamRedactor struct {
	values []string
	buffer []byte
	maxLen int
}

func newStreamRedactor(values []string) streamRedactor {
	unique := make(map[string]struct{}, len(values))
	for _, value := range values {
		if value != "" {
			unique[value] = struct{}{}
		}
	}
	sorted := make([]string, 0, len(unique))
	for value := range unique {
		sorted = append(sorted, value)
	}
	sort.Slice(sorted, func(i, j int) bool { return len(sorted[i]) > len(sorted[j]) })
	maxLen := 1
	for _, value := range sorted {
		if len(value) > maxLen {
			maxLen = len(value)
		}
	}
	return streamRedactor{values: sorted, maxLen: maxLen}
}

func (r *streamRedactor) Write(data []byte) []byte {
	r.buffer = append(r.buffer, data...)
	safeCut := len(r.buffer) - r.maxLen + 1
	if safeCut <= 0 {
		return nil
	}
	emitCut := safeCut
	for _, value := range r.values {
		start := 0
		for {
			index := bytes.Index(r.buffer[start:], []byte(value))
			if index < 0 {
				break
			}
			index += start
			if index+len(value) > safeCut && index < emitCut {
				emitCut = index
			}
			start = index + 1
		}
	}
	output := redactBytes(r.buffer[:emitCut], r.values)
	r.buffer = append(r.buffer[:0], r.buffer[emitCut:]...)
	return output
}

func (r *streamRedactor) Flush() []byte {
	output := redactBytes(r.buffer, r.values)
	r.buffer = nil
	return output
}

func redactBytes(data []byte, values []string) []byte {
	out := append([]byte(nil), data...)
	for _, value := range values {
		out = bytes.ReplaceAll(out, []byte(value), []byte("<redacted>"))
	}
	return out
}