package service

import (
	"context"
	"fmt"
	"log/slog"
	"path/filepath"
	"regexp"
	"slices"
	"strings"
	"time"

	_ "embed"

	"forge.cadoles.com/wpetit/clearcase/internal/core/model"
	"forge.cadoles.com/wpetit/clearcase/internal/core/port"
	"github.com/bornholm/genai/llm"
	"github.com/num30/go-cache"
	"github.com/pkg/errors"
)

var (
	ErrForgeNotAvailable = errors.New("forge not available")
)

//go:embed issue_system_prompt.gotmpl
var issueSystemPromptRawTemplate string

//go:embed issue_user_prompt.gotmpl
var issueUserPromptRawTemplate string

//go:embed issue_default_template.txt
var issueDefaultTemplate string

type ForgeFactory interface {
	Match(user *model.User) bool
	Create(ctx context.Context, user *model.User) (port.Forge, error)
}

type IssueManager struct {
	forgeFactories []ForgeFactory
	llmClient      llm.Client
	projectCache   *cache.Cache[[]*model.Project]
	forgeCache     *cache.Cache[port.Forge]
}

func (m *IssueManager) CreateIssue(ctx context.Context, user *model.User, projectID string, title string, body string) (string, error) {
	forge, err := m.getUserForge(ctx, user)
	if err != nil {
		return "", errors.WithStack(err)
	}

	issueURL, err := forge.CreateIssue(ctx, projectID, title, body)
	if err != nil {
		return "", errors.WithStack(err)
	}

	return issueURL, nil
}

func (m *IssueManager) GetUserProjects(ctx context.Context, user *model.User) ([]*model.Project, error) {
	cacheKey := fmt.Sprintf("%s/%s", user.Provider, user.ID)

	projects, exists := m.projectCache.Get(cacheKey)
	if !exists {
		forge, err := m.getUserForge(ctx, user)
		if err != nil {
			return nil, errors.WithStack(err)
		}

		refreshedProjects, err := forge.GetAllProjects(ctx)
		if err != nil {
			return nil, errors.WithStack(err)
		}

		slices.SortFunc(refreshedProjects, func(p1 *model.Project, p2 *model.Project) int {
			return strings.Compare(p1.Name, p2.Name)
		})

		m.projectCache.Set(cacheKey, refreshedProjects, 0)

		projects = refreshedProjects
	}

	return projects, nil
}

func (m *IssueManager) GenerateIssue(ctx context.Context, user *model.User, projectID string, issueSummary string) (string, string, string, error) {
	systemPrompt, err := m.getIssueSystemPrompt(ctx, user, projectID)
	if err != nil {
		return "", "", "", errors.WithStack(err)
	}

	slog.DebugContext(ctx, "using system prompt", slog.String("systemPrompt", systemPrompt))

	userPrompt, err := m.getIssueUserPrompt(ctx, user, projectID, issueSummary)
	if err != nil {
		return "", "", "", errors.WithStack(err)
	}

	slog.DebugContext(ctx, "using user prompt", slog.String("userPrompt", userPrompt))

	messages := []llm.Message{
		llm.NewMessage(llm.RoleSystem, systemPrompt),
		llm.NewMessage(llm.RoleUser, userPrompt),
	}

	res, err := m.llmClient.ChatCompletion(ctx, llm.WithMessages(messages...))
	if err != nil {
		return "", "", "", errors.WithStack(err)
	}

	body := res.Message().Content()

	messages = append(messages, res.Message())
	messages = append(messages, llm.NewMessage(llm.RoleUser, "Generate a title for this issue. Keep it descriptive, simple and short. Do not write anything else."))

	res, err = m.llmClient.ChatCompletion(ctx, llm.WithMessages(messages...))
	if err != nil {
		return "", "", "", errors.WithStack(err)
	}

	title := toTitle(res.Message().Content())

	messages = append(messages, res.Message())
	messages = append(messages, llm.NewMessage(llm.RoleUser, "Give me a list of questions as Markdown that could help clarify the request. Only write the list without additional headings."))

	res, err = m.llmClient.ChatCompletion(ctx, llm.WithMessages(messages...))
	if err != nil {
		return "", "", "", errors.WithStack(err)
	}

	tips := res.Message().Content()

	return title, body, tips, nil
}

func (m *IssueManager) getIssueSystemPrompt(ctx context.Context, user *model.User, projectID string) (string, error) {
	forge, err := m.getUserForge(ctx, user)
	if err != nil {
		return "", errors.WithStack(err)
	}

	issueTemplate, err := forge.GetIssueTemplate(ctx, projectID)
	if err != nil && !errors.Is(err, port.ErrFileNotFound) {
		return "", errors.WithStack(err)
	}

	if issueTemplate == "" {
		issueTemplate = issueDefaultTemplate
	}

	systemPrompt, err := llm.PromptTemplate(issueSystemPromptRawTemplate, struct {
		IssueTemplate string
	}{
		IssueTemplate: issueTemplate,
	})
	if err != nil {
		return "", errors.WithStack(err)
	}

	return systemPrompt, nil
}

func (m *IssueManager) getIssueUserPrompt(ctx context.Context, user *model.User, projectID string, issueSummary string) (string, error) {
	forge, err := m.getUserForge(ctx, user)
	if err != nil {
		return "", errors.WithStack(err)
	}

	project, err := forge.GetProject(ctx, projectID)
	if err != nil {
		return "", errors.WithStack(err)
	}

	projectLanguages, err := forge.GetProjectLanguages(ctx, projectID)
	if err != nil {
		return "", errors.WithStack(err)
	}

	resources, err := m.extractResources(ctx, forge, projectID, issueSummary)
	if err != nil {
		return "", errors.WithStack(err)
	}

	userPrompt, err := llm.PromptTemplate(issueUserPromptRawTemplate, struct {
		Summary          string
		Project          *model.Project
		ProjectLanguages []string
		Resources        []*model.Resource
	}{
		Summary:          issueSummary,
		Project:          project,
		ProjectLanguages: projectLanguages,
		Resources:        resources,
	})
	if err != nil {
		return "", errors.WithStack(err)
	}

	return userPrompt, nil
}

func (m *IssueManager) getUserForge(ctx context.Context, user *model.User) (port.Forge, error) {
	forge, exists := m.forgeCache.Get(user.AccessToken)
	if exists {
		return forge, nil
	}

	for _, f := range m.forgeFactories {
		if !f.Match(user) {
			continue
		}

		forge, err := f.Create(ctx, user)
		if err != nil {
			slog.ErrorContext(ctx, "could not retrieve user forge", slog.Any("error", errors.WithStack(err)))
			return nil, errors.WithStack(ErrForgeNotAvailable)
		}

		m.forgeCache.Set(user.AccessToken, forge, cache.DefaultExpiration)

		return forge, nil
	}

	return nil, errors.New("no forge matching user found")
}

func (m *IssueManager) extractResources(ctx context.Context, forge port.Forge, projectID string, issueSummary string) ([]*model.Resource, error) {
	resources := make([]*model.Resource, 0)

	issues, err := m.extractIssues(ctx, forge, projectID, issueSummary)
	if err != nil {
		return nil, errors.Wrap(err, "could not extract issues")
	}

	resources = append(resources, issues...)

	files, err := m.extractFiles(ctx, forge, projectID, issueSummary)
	if err != nil {
		return nil, errors.Wrap(err, "could not extract files")
	}

	resources = append(resources, files...)

	return resources, nil
}

var issueRefRegExp = regexp.MustCompile(`#([0-9]+)`)

func (m *IssueManager) extractIssues(ctx context.Context, forge port.Forge, projectID string, issueSummary string) ([]*model.Resource, error) {
	issueRefMatches := issueRefRegExp.FindAllStringSubmatch(issueSummary, -1)

	issueIDs := make([]string, 0, len(issueRefMatches))
	for _, m := range issueRefMatches {
		issueIDs = append(issueIDs, m[1])
	}

	issues, err := forge.GetIssues(ctx, projectID, issueIDs...)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	resources := make([]*model.Resource, 0, len(issues))

	for _, iss := range issues {
		if iss == nil {
			continue
		}

		resources = append(resources, &model.Resource{
			Name:    fmt.Sprintf("#%s - %s", iss.ID, iss.Title),
			Type:    "Issue",
			Syntax:  "",
			Content: iss.Body,
		})
	}

	return resources, nil
}

var fileRefRegExp = regexp.MustCompile(`(?i)(?:\/[^\/]+)+\/?[^\s]+(?:\.[^\s]+)+|[^\s]+(?:\.[^\s]+)+`)

func (m *IssueManager) extractFiles(ctx context.Context, forge port.Forge, projectID string, issueSummary string) ([]*model.Resource, error) {
	fileRefMatches := fileRefRegExp.FindAllStringSubmatch(issueSummary, -1)

	paths := make([]string, 0, len(fileRefMatches))
	for _, m := range fileRefMatches {
		paths = append(paths, m[0])
	}

	resources := make([]*model.Resource, 0)

	for _, p := range paths {
		data, err := forge.GetFile(ctx, projectID, p)
		if err != nil {
			slog.ErrorContext(ctx, "could not retrieve file", slog.Any("error", errors.WithStack(err)), slog.String("path", p))
			continue
		}

		resources = append(resources, &model.Resource{
			Name:    p,
			Type:    "File",
			Syntax:  strings.TrimPrefix(filepath.Ext(p), "."),
			Content: string(data),
		})
	}

	return resources, nil
}

func NewIssueManager(llmClient llm.Client, forgeFactories ...ForgeFactory) *IssueManager {
	return &IssueManager{
		llmClient:      llmClient,
		forgeFactories: forgeFactories,
		projectCache:   cache.New[[]*model.Project](time.Minute*5, (time.Minute*5)/2),
		forgeCache:     cache.New[port.Forge](time.Minute, time.Minute/2),
	}
}

func toTitle(str string) string {
	str = strings.ToLower(str)
	return strings.ToUpper(string(str[0])) + str[1:]
}