package pi

import (
	"context"
	"crypto/sha256"
	"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"`
}

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) (retErr error) {
	if !choicePattern.MatchString(value.Provider) || !choicePattern.MatchString(value.Model) {
		return errors.New("provider and model must be supported identifiers")
	}
	if value.Thinking != "low" && value.Thinking != "medium" && value.Thinking != "high" {
		return errors.New("thinking must be low, medium, or high")
	}
	before, err := renderedCore(ctx, runner)
	if err != nil { return err }
	args := append([]string{"exec", "-T", "core", "curl", "-fsS"}, internalIdentityHeaders...)
	args = append(args, "http://127.0.0.1:8787/models")
	models, err := runCompose(ctx, runner, args...)
	if err != nil {
		return commandError("Pi options check", models, err)
	}
	var payload struct {
		Models []struct {
			Provider string `json:"provider"`
			ID       string `json:"id"`
		} `json:"models"`
	}
	if json.Unmarshal([]byte(models.Stdout), &payload) != nil || len(payload.Models) == 0 {
		return errors.New("Pi options response is invalid or empty")
	}
	found := false
	for _, model := range payload.Models {
		if model.Provider == value.Provider && model.ID == value.Model {
			found = true
		}
	}
	if !found {
		return errors.New("provider/model is not in Pi options")
	}
	settingsArgs := append([]string{"exec", "-T", "core", "curl", "-fsS"}, internalIdentityHeaders...)
	settingsArgs = append(settingsArgs, "http://127.0.0.1:8787/settings")
	oldResult, err := runCompose(ctx, runner, settingsArgs...)
	if err != nil { return commandError("Pi installation settings capture", oldResult, err) }
	var old Defaults
	if json.Unmarshal([]byte(oldResult.Stdout), &old) != nil || old.Provider == "" || old.Model == "" || old.Thinking == "" { return errors.New("Pi installation settings capture is invalid") }
	wrote := false
	defer func() {
		if retErr != nil && wrote {
			result, restoreErr := runCompose(context.Background(), runner, "exec", "-T", "core", "node", "/app/backend/dist/settings/settings-cli.js", "--provider", old.Provider, "--model", old.Model, "--thinking", old.Thinking)
			if restoreErr != nil || result.ExitCode != 0 { retErr = fmt.Errorf("%w; previous Pi settings could not be restored: recovery required", retErr) }
		}
	}()
	result, err := runCompose(ctx, runner, "exec", "-T", "core", "node", "/app/backend/dist/settings/settings-cli.js", "--provider", value.Provider, "--model", value.Model, "--thinking", value.Thinking)
	if err != nil { return commandError("Pi installation settings write", result, err) }
	wrote = true
	settings, err := runCompose(ctx, runner, settingsArgs...)
	if err != nil { return commandError("Pi installation settings read-back", settings, err) }
	var saved Defaults
	if json.Unmarshal([]byte(settings.Stdout), &saved) != nil || saved.Provider != value.Provider || saved.Model != value.Model || saved.Thinking != value.Thinking {
		return errors.New("Pi installation settings read-back did not match requested provider, model, and thinking")
	}
	after, err := renderedCore(ctx, runner)
	if err != nil { return err }
	if before.ConfigurationSHA != after.ConfigurationSHA { return errors.New("external endpoint configuration changed while configuring Pi") }
	return 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
	}
	if _, err := Status(ctx, runner); err != nil {
		return err
	}
	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)
}

// Test performs the pre-Task-8 composite smoke through core's private loopback endpoint.
func Test(ctx context.Context, runner Runner) error {
	if _, err := Status(ctx, runner); err != nil {
		return err
	}
	for _, path := range []string{"health", "models", "settings"} {
		args := []string{"exec", "-T", "core", "curl", "-fsS"}
		if path != "health" { args = append(args, internalIdentityHeaders...) }
		args = append(args, "http://127.0.0.1:8787/"+path)
		result, err := runCompose(ctx, runner, args...)
		if err != nil {
			return commandError("Pi smoke check", result, err)
		}
		var payload any
		if err := json.Unmarshal([]byte(result.Stdout), &payload); err != nil {
			return fmt.Errorf("Pi smoke check returned invalid %s response", path)
		}
		object, ok := payload.(map[string]any)
		if !ok {
			return fmt.Errorf("Pi smoke check returned invalid %s response", path)
		}
		switch path {
		case "health":
			if object["status"] != "ok" { return errors.New("Pi smoke health response is not ready") }
		case "models":
			models, ok := object["models"].([]any)
			if !ok || len(models) == 0 { return errors.New("Pi smoke models response is empty") }
			valid := false
			for _, item := range models { if model, ok := item.(map[string]any); ok && stringField(model, "provider") != "" && stringField(model, "id") != "" { valid = true; break } }
			if !valid { return errors.New("Pi smoke models response has no provider/model choices") }
		case "settings":
			if stringField(object, "provider") == "" || stringField(object, "model") == "" || stringField(object, "thinking") == "" { return errors.New("Pi smoke settings response is incomplete") }
		}
	}
	return nil
}

func stringField(value map[string]any, key string) string { text, _ := value[key].(string); return strings.TrimSpace(text) }

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 struct {
		Services map[string]struct {
			Image       string         `json:"image"`
			Environment map[string]any `json:"environment"`
		} `json:"services"`
	}
	if err := json.Unmarshal([]byte(result.Stdout), &document); err != nil {
		return Image{}, errors.New("Compose returned invalid rendered configuration")
	}
	core, exists := document.Services["core"]
	if !exists || core.Image == "" {
		return Image{}, errors.New("rendered Compose configuration has no core image")
	}
	endpoint, exists := core.Environment["THT_LLM_URL"].(string)
	if !exists || strings.TrimSpace(endpoint) == "" {
		return Image{}, errors.New("THT_LLM_URL must be configured before Pi lifecycle operations")
	}
	digest := sha256.Sum256([]byte(result.Stdout))
	return Image{Reference: core.Image, 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 }