package preflight

import (
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"io/fs"
	"os"
	"path/filepath"
	"slices"
	"strings"

	"github.com/aritmolab/thothii/tools/tht/internal/config"
	"github.com/aritmolab/thothii/tools/tht/internal/safeio"
	"github.com/aritmolab/thothii/tools/tht/internal/version"
	"gopkg.in/yaml.v3"
)

type Plan struct {
	SchemaVersion      int                 `json:"schema_version"`
	ValidatorProtocol  int                 `json:"validator_protocol"`
	Validator          version.Info        `json:"validator"`
	Installation       config.Installation `json:"installation"`
	Release            Manifest            `json:"release"`
	Platform           string              `json:"platform"`
	WorkspaceDirectory string              `json:"workspace_directory"`
	WorkspaceRevision  string              `json:"workspace_revision"`
	Inputs             []string            `json:"inputs"`
	AbsentInputs       []string            `json:"absent_inputs"`
	InputSeal          string              `json:"input_seal"`
	Report             Report              `json:"report"`
}

func invalidPlan() error {
	return errors.New("plan inputs changed or protected plan files are unavailable; repeat validation and produce a new plan")
}

// CaptureInputs gives a value-free freshness guard around live probes and document validation.
func CaptureInputs(paths []string, workspace string, absent ...string) (func() bool, error) {
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		return nil, invalidPlan()
	}
	probe := Plan{Inputs: paths, AbsentInputs: absent}
	before, err := seal(probe, key)
	if err != nil {
		return nil, err
	}
	files, err := treeFiles(workspace, true)
	if err != nil {
		return nil, err
	}
	return func() bool {
		after, err := seal(probe, key)
		current, treeErr := treeFiles(workspace, true)
		return err == nil && treeErr == nil && hmac.Equal([]byte(before), []byte(after)) && slices.Equal(files, current)
	}, nil
}

// A separate owner-only random key prevents public/offline guessing of low-entropy secrets.
// Live prerequisites must still be rechecked immediately before any execution or resumption.
func seal(plan Plan, key []byte) (string, error) {
	for _, path := range plan.AbsentInputs {
		if _, err := os.Lstat(path); !errors.Is(err, os.ErrNotExist) {
			return "", invalidPlan()
		}
	}
	mac := hmac.New(sha256.New, key)
	plan.InputSeal = ""
	data, err := json.Marshal(plan)
	if err != nil {
		return "", invalidPlan()
	}
	mac.Write(data)
	var total int
	for _, path := range plan.Inputs {
		contents, err := safeio.ReadCanonicalRegular(path, 32<<20)
		if err != nil {
			return "", invalidPlan()
		}
		total += len(contents)
		if total > 256<<20 {
			return "", invalidPlan()
		}
		length, _ := json.Marshal([]any{path, len(contents)})
		mac.Write(length)
		mac.Write(contents)
	}
	return hex.EncodeToString(mac.Sum(nil)), nil
}

func AbsentOverrides(installation config.Installation) []string {
	paths := []string{}
	for _, path := range installation.Overrides {
		if _, err := os.Lstat(path); errors.Is(err, os.ErrNotExist) {
			paths = append(paths, path)
		}
	}
	return paths
}
func WritePlan(path string, plan *Plan, guards ...func() bool) error {
	if !plan.Report.OK || plan.ValidatorProtocol != Protocol || !filepath.IsAbs(path) {
		return invalidPlan()
	}
	if exists, err := safeio.PreflightPrivateDirectory(filepath.Dir(path)); err != nil || !exists {
		return invalidPlan()
	}
	for _, target := range []string{path, path + ".key"} {
		if _, err := os.Lstat(target); !errors.Is(err, os.ErrNotExist) {
			return invalidPlan()
		}
	}
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		return invalidPlan()
	}
	var err error
	plan.InputSeal, err = seal(*plan, key)
	if err != nil {
		return err
	}
	for _, guard := range guards {
		if guard == nil || !guard() {
			return invalidPlan()
		}
	}
	data, _ := json.MarshalIndent(plan, "", "  ")
	if err := safeio.WriteCanonicalNewPrivateFile(path+".key", key, 0o600); err != nil {
		return invalidPlan()
	}
	if err := safeio.WriteCanonicalNewPrivateFile(path, append(data, '\n'), 0o600); err != nil {
		_ = safeio.RemoveCanonicalPrivateRegular(path + ".key")
		return invalidPlan()
	}
	return nil
}
func VerifyPlanInputs(path string) error {
	data, err := safeio.ReadCanonicalPrivateRegular(path, 4<<20)
	if err != nil {
		return invalidPlan()
	}
	key, err := safeio.ReadCanonicalPrivateRegular(path+".key", 32)
	if err != nil || len(key) != 32 {
		return invalidPlan()
	}
	var plan Plan
	if json.Unmarshal(data, &plan) != nil || plan.SchemaVersion != 1 || plan.ValidatorProtocol != Protocol || !plan.Report.OK || len(plan.Inputs) == 0 || len(plan.Inputs) > 10000 {
		return invalidPlan()
	}
	actual, err := seal(plan, key)
	if err != nil || !hmac.Equal([]byte(actual), []byte(plan.InputSeal)) {
		return invalidPlan()
	}
	// Detect added or removed workspace files as well as changes to known file bytes.
	if plan.WorkspaceDirectory != "" {
		files, err := treeFiles(plan.WorkspaceDirectory, true)
		if err != nil {
			return invalidPlan()
		}
		for _, file := range files {
			if !slices.Contains(plan.Inputs, file) {
				return invalidPlan()
			}
		}
	}
	return nil
}
func treeFiles(root string, skipGit bool) ([]string, error) {
	paths := []string{}
	count := 0
	err := filepath.WalkDir(root, func(path string, entry fs.DirEntry, err error) error {
		if err != nil {
			return invalidPlan()
		}
		count++
		if count > 10000 {
			return invalidPlan()
		}
		if skipGit && entry.Name() == ".git" {
			if entry.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}
		if entry.IsDir() {
			return nil
		}
		if !entry.Type().IsRegular() {
			return invalidPlan()
		}
		paths = append(paths, path)
		return nil
	})
	return paths, err
}

// CollectInputs fingerprints exact prepared contents, with normalized configuration in Plan.
// Referenced credentials are sealed, never copied. Git object stores are excluded.
func CollectInputs(installation config.Installation, workspace, bootstrap, manifest string) ([]string, string, error) {
	paths := []string{installation.Path, installation.EnvFile, bootstrap, manifest}
	for _, root := range []string{workspace, installation.AuthenticationDirectory()} {
		files, err := treeFiles(root, root == workspace)
		if err != nil {
			return nil, "", err
		}
		paths = append(paths, files...)
	}
	secrets, err := installation.SecretFiles()
	if err != nil {
		return nil, "", invalidPlan()
	}
	for _, path := range secrets {
		paths = append(paths, path)
	}
	data, err := safeio.ReadCanonicalPrivateRegular(bootstrap, 1<<20)
	if err != nil {
		return nil, "", invalidPlan()
	}
	var bindings struct {
		Databases []struct {
			SecretFiles         map[string]string `yaml:"secretFiles"`
			EvidenceSecretFiles map[string]string `yaml:"evidenceSecretFiles"`
		} `yaml:"databases"`
	}
	if yaml.Unmarshal(data, &bindings) != nil {
		return nil, "", invalidPlan()
	}
	for _, entry := range bindings.Databases {
		for _, values := range []map[string]string{entry.SecretFiles, entry.EvidenceSecretFiles} {
			for _, path := range values {
				paths = append(paths, path)
			}
		}
	}
	m, err := LoadManifest(manifest)
	if err != nil {
		return nil, "", err
	}
	for name := range m.Files {
		paths = append(paths, filepath.Join(filepath.Dir(manifest), filepath.FromSlash(name)))
	}
	for _, path := range installation.Overrides {
		if _, err := os.Lstat(path); err == nil {
			paths = append(paths, path)
		}
	}
	revision := "content-snapshot"
	head := filepath.Join(workspace, ".git", "HEAD")
	if data, err := safeio.ReadCanonicalRegular(head, 1024); err == nil {
		paths = append(paths, head)
		value := strings.TrimSpace(string(data))
		if strings.HasPrefix(value, "ref: refs/") {
			ref := strings.TrimPrefix(value, "ref: ")
			if safeRelative(ref) {
				path := filepath.Join(workspace, ".git", filepath.FromSlash(ref))
				if data, err := safeio.ReadCanonicalRegular(path, 1024); err == nil {
					paths = append(paths, path)
					value = strings.TrimSpace(string(data))
				}
			}
		}
		if len(value) == 40 {
			if _, err := hex.DecodeString(value); err == nil {
				revision = value
			}
		}
	}
	slices.Sort(paths)
	paths = slices.Compact(paths)
	return paths, revision, nil
}

func AddRuntimeObligations(report *Report) {
	for _, check := range []Check{
		{"container-network", "deferred-to-runtime", "bindings", "Repeat authenticated DWH and external connectivity checks from the core network."},
		{"catalog-initialization", "deferred-to-runtime", "catalog", "Apply migrations and verify Catalog health plus prepared binding import."},
		{"pi-operation", "deferred-to-runtime", "release.components.pi", "Verify the bundled Pi version and authenticated provider/model smoke operation inside core; do not install Pi on the host."},
		{"local-embedding", "deferred-to-runtime", "modelCatalog.embedding", "Initialize the local embedding model and verify returned vector dimensions."},
		{"workspace-preprocessing", "deferred-to-runtime", "workspaces", "Sync the exact verified workspace contents, materialize Evidence, preprocess and verify collections."},
		{"workspace-readiness", "deferred-to-runtime", "workspaces", "Complete required administrative and human review gates before claiming final readiness."},
	} {
		report.Checks = append(report.Checks, check)
	}
}