package pi

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"regexp"
	"strings"

	"github.com/aritmolab/thothii/tools/thothctl/internal/compose"
)

var choicePattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._/-]{0,127}$`)

type Defaults struct {
	Provider string `json:"provider"`
	Model    string `json:"model"`
	Thinking string `json:"thinking"`
}

type ModelOption struct {
	Provider string `json:"provider"`
	ID       string `json:"id"`
}

type piOptions struct {
	Providers []string      `json:"providers"`
	Models    []ModelOption `json:"models"`
	Reasoning []string      `json:"reasoning"`
}

type settingsFileSnapshot struct {
	Exists    bool   `json:"exists"`
	RawBase64 string `json:"rawBase64"`
}

var internalIdentityHeaders = []string{
	"-H", "x-thoth-principal-issuer: thothctl",
	"-H", "x-thoth-principal-subject: thothctl-maintenance",
	"-H", "x-thoth-principal-display-name: Thothctl maintenance",
	"-H", "x-thoth-is-admin: 1",
}

// Configure changes the backend's real installation settings through a core-side helper. It
// deliberately has no secret or endpoint input: external endpoints remain Compose-owned.
func Configure(ctx context.Context, runner Runner, value Defaults) error {
	if !choicePattern.MatchString(value.Provider) || !choicePattern.MatchString(value.Model) {
		return errors.New("provider and model must be supported identifiers")
	}
	before, err := renderedCore(ctx, runner)
	if err != nil {
		return err
	}
	options, err := configurationOptions(ctx, runner)
	if err != nil {
		return err
	}
	found := false
	for _, model := range options.Models {
		if model.Provider == value.Provider && model.ID == value.Model {
			found = true
		}
	}
	if !found {
		return errors.New("provider/model is not in Pi options")
	}
	thinkingFound := false
	for _, reasoning := range options.Reasoning {
		if reasoning == value.Thinking {
			thinkingFound = true
		}
	}
	if !thinkingFound {
		return errors.New("thinking is not in Pi options")
	}
	old, err := captureSettingsFile(ctx, runner)
	if err != nil {
		return err
	}
	oldEffective, err := readEffectiveSettings(ctx, runner)
	if err != nil {
		return err
	}
	restore := func(cause error) error {
		if restoreErr := restoreSettingsFile(context.Background(), runner, old); restoreErr != nil {
			return fmt.Errorf("%w; previous Pi settings restoration could not be verified: %w", cause, restoreErr)
		}
		restoredEffective, restoreErr := readEffectiveSettings(context.Background(), runner)
		if restoreErr != nil || !bytes.Equal(restoredEffective, oldEffective) {
			return fmt.Errorf("%w; previous effective Pi settings could not be verified: recovery required", cause)
		}
		return cause
	}
	result, err := writeDefaults(ctx, runner, value)
	if err != nil {
		return restore(commandError("Pi installation settings write", result, err))
	}
	settings, err := readEffectiveSettings(ctx, runner)
	if err != nil {
		return restore(err)
	}
	var saved Defaults
	if json.Unmarshal(settings, &saved) != nil || saved.Provider != value.Provider || saved.Model != value.Model || saved.Thinking != value.Thinking {
		return restore(errors.New("Pi installation settings read-back did not match requested provider, model, and thinking"))
	}
	after, err := renderedCore(ctx, runner)
	if err != nil {
		return restore(err)
	}
	if before.ConfigurationSHA != after.ConfigurationSHA {
		return restore(errors.New("external endpoint configuration changed while configuring Pi"))
	}
	return nil
}

func ConfigurationOptions(ctx context.Context, runner Runner) ([]ModelOption, error) {
	options, err := configurationOptions(ctx, runner)
	if err != nil {
		return nil, err
	}
	return options.Models, nil
}

func configurationOptions(ctx context.Context, runner Runner) (piOptions, error) {
	args := append([]string{"exec", "-T", "core", "curl", "-fsS"}, internalIdentityHeaders...)
	args = append(args, "http://127.0.0.1:8787/pi-management/options")
	result, err := runCompose(ctx, runner, args...)
	if err != nil {
		return piOptions{}, commandError("Pi options check", result, err)
	}
	var payload piOptions
	if json.Unmarshal([]byte(result.Stdout), &payload) != nil || len(payload.Providers) == 0 || len(payload.Models) == 0 || len(payload.Reasoning) == 0 {
		return piOptions{}, errors.New("Pi options response is invalid or empty")
	}
	providers := make(map[string]bool, len(payload.Providers))
	for _, provider := range payload.Providers {
		if !choicePattern.MatchString(provider) || providers[provider] {
			return piOptions{}, errors.New("Pi options response contains an invalid provider")
		}
		providers[provider] = true
	}
	models := make(map[string]bool, len(payload.Models))
	for _, option := range payload.Models {
		key := option.Provider + "\x00" + option.ID
		if !providers[option.Provider] || !choicePattern.MatchString(option.ID) || models[key] {
			return piOptions{}, errors.New("Pi options response contains an invalid provider/model")
		}
		models[key] = true
	}
	reasoning := make(map[string]bool, len(payload.Reasoning))
	for _, value := range payload.Reasoning {
		if (value != "low" && value != "medium" && value != "high") || reasoning[value] {
			return piOptions{}, errors.New("Pi options response contains an invalid reasoning choice")
		}
		reasoning[value] = true
	}
	return payload, nil
}

func writeDefaults(ctx context.Context, runner Runner, value Defaults) (compose.Result, error) {
	return runCompose(ctx, runner, "exec", "-T", "core", "node", "/app/backend/dist/settings/settings-cli.js", "--provider", value.Provider, "--model", value.Model, "--thinking", value.Thinking)
}

func captureSettingsFile(ctx context.Context, runner Runner) (settingsFileSnapshot, error) {
	result, err := runCompose(ctx, runner, "exec", "-T", "core", "node", "/app/backend/dist/settings/settings-cli.js", "--snapshot")
	if err != nil {
		return settingsFileSnapshot{}, commandError("Pi installation settings snapshot", result, err)
	}
	var snapshot settingsFileSnapshot
	if json.Unmarshal([]byte(result.Stdout), &snapshot) != nil {
		return settingsFileSnapshot{}, errors.New("Pi installation settings snapshot is invalid")
	}
	raw, decodeErr := base64.StdEncoding.DecodeString(snapshot.RawBase64)
	if decodeErr != nil || base64.StdEncoding.EncodeToString(raw) != snapshot.RawBase64 || (!snapshot.Exists && len(raw) != 0) {
		return settingsFileSnapshot{}, errors.New("Pi installation settings snapshot is invalid")
	}
	return snapshot, nil
}

func restoreSettingsFile(ctx context.Context, runner Runner, snapshot settingsFileSnapshot) error {
	payload, err := json.Marshal(snapshot)
	if err != nil {
		return errors.New("Pi installation settings snapshot could not be encoded")
	}
	args := []string{"compose", "exec", "-T", "core", "node", "/app/backend/dist/settings/settings-cli.js", "--restore"}
	result, restoreErr := runner.Run(ctx, args, bytes.NewReader(payload))
	verified, verifyErr := captureSettingsFile(ctx, runner)
	if restoreErr != nil {
		cause := commandError("Pi installation settings restore", result, restoreErr)
		if verifyErr == nil && verified == snapshot {
			return recoveryRequired("previous Pi settings bytes were restored but durability was not acknowledged", cause)
		}
		return cause
	}
	if verifyErr == nil && verified == snapshot {
		return nil
	}
	return errors.New("Pi installation settings restore did not reproduce the exact prior file state")
}

func readEffectiveSettings(ctx context.Context, runner Runner) ([]byte, error) {
	args := append([]string{"exec", "-T", "core", "curl", "-fsS"}, internalIdentityHeaders...)
	args = append(args, "http://127.0.0.1:8787/settings")
	result, err := runCompose(ctx, runner, args...)
	if err != nil {
		return nil, commandError("Pi installation settings read-back", result, err)
	}
	var settings map[string]json.RawMessage
	if json.Unmarshal([]byte(result.Stdout), &settings) != nil || settings == nil {
		return nil, errors.New("Pi installation settings read-back is invalid")
	}
	canonical, err := json.Marshal(settings)
	if err != nil {
		return nil, errors.New("Pi installation settings read-back could not be normalized")
	}
	return canonical, nil
}

// Runner is the narrow, shell-free command boundary shared with thothctl.
type Runner interface {
	Run(context.Context, []string, io.Reader) (compose.Result, error)
}

// Status reports the image-bundled Pi version without using a host Pi executable.
func Status(ctx context.Context, runner Runner) (string, error) {
	result, err := runCompose(ctx, runner, "exec", "-T", "core", "pi", "--version")
	if err != nil {
		return "", commandError("Pi version check", result, err)
	}
	version := strings.TrimSpace(result.Stdout)
	if version == "" {
		return "", errors.New("Pi version check returned no version")
	}
	return version, nil
}

// Doctor verifies the installation-side invariants Pi needs before an update.
func Doctor(ctx context.Context, runner Runner) error {
	if _, err := renderedCore(ctx, runner); err != nil {
		return err
	}
	actual, err := Status(ctx, runner)
	if err != nil {
		return err
	}
	expected, label, err := expectedVersions(ctx, runner)
	if err != nil {
		return err
	}
	if actual != expected || actual != label {
		return errors.New("Pi version does not match the image PI_VERSION and io.thothii.pi.version contract")
	}
	for _, check := range [][]string{
		{"exec", "-T", "core", "sh", "-ceu", "test -w /home/thoth/.pi"},
		{"exec", "-T", "core", "sh", "-ceu", "test -r /home/thoth/.pi/agent/auth.json"},
		{"exec", "-T", "core", "curl", "-fsS", "http://127.0.0.1:8787/health"},
	} {
		result, err := runCompose(ctx, runner, check...)
		if err != nil {
			return commandError("Pi preflight check", result, err)
		}
	}
	return Test(ctx, runner)
}

func expectedVersions(ctx context.Context, runner Runner) (string, string, error) {
	environment, err := runCompose(ctx, runner, "exec", "-T", "core", "sh", "-ceu", `printf '%s\n' "${PI_VERSION:-}"`)
	if err != nil {
		return "", "", commandError("Pi expected-version check", environment, err)
	}
	container, err := runCompose(ctx, runner, "ps", "-q", "core")
	if err != nil || strings.TrimSpace(container.Stdout) == "" {
		return "", "", commandError("Pi image-label check", container, err)
	}
	label, err := runner.Run(ctx, []string{"inspect", "--format", `{{ index .Config.Labels "io.thothii.pi.version" }}`, strings.TrimSpace(container.Stdout)}, nil)
	if err != nil {
		return "", "", commandError("Pi image-label check", label, err)
	}
	expectedValue, labelValue := strings.TrimSpace(environment.Stdout), strings.TrimSpace(label.Stdout)
	if expectedValue == "" || labelValue == "" {
		return "", "", errors.New("Pi image expected-version contract is empty")
	}
	return expectedValue, labelValue, nil
}

// Test retains the direct image-version signal, then delegates all Pi configuration/provider smoke
// validation to core's dedicated, admin-only Pi Management endpoint.
func Test(ctx context.Context, runner Runner) error {
	if _, err := Status(ctx, runner); err != nil {
		return err
	}
	args := append([]string{"exec", "-T", "core", "curl", "-fsS", "-X", "POST"}, internalIdentityHeaders...)
	args = append(args, "http://127.0.0.1:8787/pi-management/test")
	smoke, err := runCompose(ctx, runner, args...)
	if err != nil {
		return commandError("Pi smoke check", smoke, err)
	}
	var smokePayload struct {
		Ready bool `json:"ready"`
	}
	if json.Unmarshal([]byte(smoke.Stdout), &smokePayload) != nil || !smokePayload.Ready {
		return errors.New("Pi smoke response is not ready")
	}
	return nil
}

func renderedCore(ctx context.Context, runner Runner) (Image, error) {
	result, err := runCompose(ctx, runner, "config", "--format", "json")
	if err != nil {
		return Image{}, commandError("Compose configuration check", result, err)
	}
	var document map[string]any
	if err := json.Unmarshal([]byte(result.Stdout), &document); err != nil {
		return Image{}, errors.New("Compose returned invalid rendered configuration")
	}
	services, ok := document["services"].(map[string]any)
	if !ok {
		return Image{}, errors.New("rendered Compose configuration has no services")
	}
	core, ok := services["core"].(map[string]any)
	reference, _ := core["image"].(string)
	if !ok || reference == "" {
		return Image{}, errors.New("rendered Compose configuration has no core image")
	}
	environment, _ := core["environment"].(map[string]any)
	endpoint, exists := environment["THT_LLM_URL"].(string)
	if !exists || strings.TrimSpace(endpoint) == "" {
		return Image{}, errors.New("THT_LLM_URL must be configured before Pi lifecycle operations")
	}
	// Lifecycle overrides intentionally replace only core.image. Normalize that field so the
	// non-secret configuration digest continues to detect endpoint/mount/configuration drift.
	core["image"] = "<lifecycle-image>"
	normalized, err := json.Marshal(document)
	if err != nil {
		return Image{}, errors.New("Compose configuration could not be normalized")
	}
	digest := sha256.Sum256(normalized)
	return Image{Reference: reference, ConfigurationSHA: fmt.Sprintf("%x", digest[:])}, nil
}

func runCompose(ctx context.Context, runner Runner, args ...string) (compose.Result, error) {
	return runner.Run(ctx, append([]string{"compose"}, args...), nil)
}

func commandError(label string, result compose.Result, err error) error {
	if result.ExitCode != 0 {
		return commandFailure{message: fmt.Sprintf("%s failed (exit %d)", label, result.ExitCode), exitCode: result.ExitCode}
	}
	return commandFailure{message: fmt.Sprintf("%s failed", label)}
}

type commandFailure struct {
	message  string
	exitCode int
}

func (e commandFailure) Error() string { return e.message }

// ExitCode exposes a Docker child exit code without exposing its output.
func (e commandFailure) ExitCode() int { return e.exitCode }