package project

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/mathiasbq/supervisor/internal/githubclient"
	"github.com/mathiasbq/supervisor/internal/mcpclient"
)

type createArgs struct {
	Name        string `json:"name"`
	Description string `json:"description"`
	Hypothesis  string `json:"hypothesis"`
	Folder      string `json:"folder"`
	Stack       string `json:"stack"`
	Private     bool   `json:"private"`
}

type createResult struct {
	GiteaURL  string `json:"gitea_url"`
	GitHubURL string `json:"github_url"`
	IssueURL  string `json:"issue_url"`
	NextSteps string `json:"next_steps"`

	// Reached records the steps that completed. Populated on partial failure
	// so callers can resume manually instead of guessing what already ran.
	Reached []string `json:"reached,omitempty"`

	// FailedStep is non-empty when a downstream gitea-mcp call returned an
	// error; the error itself is surfaced via the JSON-RPC error response,
	// this field tells the operator which step it happened in.
	FailedStep string `json:"failed_step,omitempty"`
}

func errUnknownTool(name string) error { return fmt.Errorf("unknown tool: %s", name) }

// step names — must match what we surface in failed_step / reached.
const (
	stepCreateRepo   = "create_repo"
	stepCreateGitHub = "create_github_repo"
	stepMirror       = "mirror"
	stepInfraCommit  = "infra_commit"
	stepIssue        = "issue"
)

func (s *Skill) handleCreate(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
	var args createArgs
	if err := json.Unmarshal(raw, &args); err != nil {
		return nil, fmt.Errorf("parse args: %w", err)
	}
	if err := validate(args); err != nil {
		return nil, err
	}

	tmpl := templateFor(args.Stack)
	giteaURL := fmt.Sprintf("http://gitea.d-ma.be/%s/%s", s.cfg.GiteaOwner, args.Name)
	githubURL := fmt.Sprintf("https://github.com/%s/%s", s.cfg.GitHubOwner, args.Name)

	res := createResult{
		GiteaURL:  giteaURL,
		GitHubURL: githubURL,
	}

	// Step 1: create_project_from_template. If the repo already exists,
	// gitea-mcp returns -32003 Conflict; we treat that as idempotent success
	// and continue to the next steps so re-running self-heals partial runs.
	existed, err := s.callCreateRepo(ctx, args, tmpl)
	if err != nil {
		return marshalPartial(res, stepCreateRepo, err)
	}
	res.Reached = append(res.Reached, stepCreateRepo)

	// Step 2: create empty GitHub repo. Gitea's push-mirror cannot push
	// to a non-existent remote, so the destination must exist before
	// step 3 configures the mirror. Skipped when GitHub client is unset
	// (degraded mode — see Config.GitHub doc).
	if s.cfg.GitHub != nil {
		if err := s.callCreateGitHubRepo(ctx, args); err != nil && !errors.Is(err, githubclient.ErrAlreadyExists) {
			return marshalPartial(res, stepCreateGitHub, err)
		}
		res.Reached = append(res.Reached, stepCreateGitHub)
	}

	// Step 3: configure push mirror to GitHub. Idempotent: if a mirror with
	// the same remote already exists, gitea-mcp returns Conflict; we swallow it.
	if err := s.callMirror(ctx, args.Name); err != nil {
		if !isConflict(err) {
			return marshalPartial(res, stepMirror, err)
		}
	}
	res.Reached = append(res.Reached, stepMirror)

	// Step 3: commit staging namespace manifest to infra repo. Done before
	// the issue so the staging env is reconciling by the time the issue lands.
	branch := fmt.Sprintf("staging/%s", args.Name)
	if err := s.callInfraCommit(ctx, args.Name, branch); err != nil {
		if !isConflict(err) {
			return marshalPartial(res, stepInfraCommit, err)
		}
	}
	res.Reached = append(res.Reached, stepInfraCommit)

	// Step 4: open the experiment-brief issue on the new repo.
	issueURL, err := s.callIssue(ctx, args, existed)
	if err != nil {
		return marshalPartial(res, stepIssue, err)
	}
	res.IssueURL = issueURL
	res.Reached = append(res.Reached, stepIssue)

	folder := args.Folder
	if folder == "" {
		folder = "."
	}
	res.NextSteps = fmt.Sprintf(
		"cd ~/dev/%s/%s && task new-project -- %s personal %s %s && git remote add origin http://gitea.d-ma.be/%s/%s.git && git push -u origin main",
		folder, args.Name, args.Name, folder, args.Stack, s.cfg.GiteaOwner, args.Name,
	)

	return marshalResult(res)
}

// callCreateRepo invokes create_project_from_template. Returns (existed, err)
// where existed=true means the destination was already present and we should
// treat it as a no-op success (idempotency).
func (s *Skill) callCreateRepo(ctx context.Context, args createArgs, template string) (bool, error) {
	var out struct {
		HTMLURL string `json:"html_url"`
	}
	err := s.cfg.Client.CallTool(ctx, "create_project_from_template", map[string]any{
		"owner":         s.cfg.GiteaOwner,
		"name":          args.Name,
		"description":   args.Description,
		"private":       args.Private,
		"template_name": template,
	}, &out)
	if err == nil {
		return false, nil
	}
	if isConflict(err) {
		return true, nil
	}
	return false, err
}

// callCreateGitHubRepo creates the empty destination repo on GitHub.
// auto_init=false in githubclient so first push from gitea doesn't conflict
// with an auto-generated README.
func (s *Skill) callCreateGitHubRepo(ctx context.Context, args createArgs) error {
	_, err := s.cfg.GitHub.CreateRepo(ctx, args.Name, args.Description, args.Private)
	return err
}

// callMirror configures the push mirror to GitHub.
func (s *Skill) callMirror(ctx context.Context, name string) error {
	remote := fmt.Sprintf("https://github.com/%s/%s.git", s.cfg.GitHubOwner, name)
	return s.cfg.Client.CallTool(ctx, "repo_mirror_push", map[string]any{
		"owner":           s.cfg.GiteaOwner,
		"name":            name,
		"action":          "add",
		"remote_address":  remote,
		"remote_username": s.cfg.GitHubOwner,
		"remote_password": s.cfg.GitHubPAT,
		"interval":        "8h0m0s",
		"sync_on_commit":  true,
	}, nil)
}

// callInfraCommit writes the staging namespace manifest into the infra repo
// on a dedicated branch. Flux picks it up after merge.
func (s *Skill) callInfraCommit(ctx context.Context, name, branch string) error {
	manifest := stagingNamespaceManifest(name, time.Now().UTC().Format(time.RFC3339))
	return s.cfg.Client.CallTool(ctx, "file_write_branch", map[string]any{
		"owner":   s.cfg.GiteaOwner,
		"name":    s.cfg.InfraRepo,
		"path":    fmt.Sprintf("k3s/staging/%s/namespace.yaml", name),
		"content": manifest,
		"branch":  branch,
		"base":    "main",
		"message": fmt.Sprintf("feat(staging): add namespace for %s\n\nGenerated by hyperguild project_create.", name),
	}, nil)
}

// callIssue opens the experiment-brief issue on the newly-created repo.
// existed=true (repo pre-existed) still posts a new brief — repeated runs
// can intentionally restate intent without colliding.
func (s *Skill) callIssue(ctx context.Context, args createArgs, existed bool) (string, error) {
	body := experimentBrief(args, existed)
	var out struct {
		HTMLURL string `json:"html_url"`
	}
	err := s.cfg.Client.CallTool(ctx, "issue_create", map[string]any{
		"owner": s.cfg.GiteaOwner,
		"name":  args.Name,
		"title": "experiment brief: " + args.Description,
		"body":  body,
	}, &out)
	if err != nil {
		return "", err
	}
	return out.HTMLURL, nil
}

func stagingNamespaceManifest(name, createdAt string) string {
	return fmt.Sprintf(`apiVersion: v1
kind: Namespace
metadata:
  name: staging-%s
  labels:
    managed-by: hyperguild
    project: %s
    created-at: "%s"
`, name, name, createdAt)
}

func experimentBrief(args createArgs, existed bool) string {
	var b strings.Builder
	b.WriteString("## Hypothesis\n\n")
	b.WriteString(args.Hypothesis)
	b.WriteString("\n\n## Description\n\n")
	b.WriteString(args.Description)
	b.WriteString("\n\n## Stack\n\n`")
	b.WriteString(args.Stack)
	b.WriteString("`\n\n## Provisioning\n\n")
	b.WriteString("- Repo created from `template-")
	b.WriteString(args.Stack)
	b.WriteString("` on Gitea.\n")
	b.WriteString("- Push-mirror configured to GitHub.\n")
	b.WriteString("- Staging namespace manifest committed to infra repo.\n\n")
	if existed {
		b.WriteString("> Note: this repo already existed when `project_create` ran — provisioning steps were re-applied idempotently.\n")
	}
	return b.String()
}

func validate(args createArgs) error {
	if args.Name == "" {
		return errors.New("name is required")
	}
	if args.Description == "" {
		return errors.New("description is required")
	}
	if args.Hypothesis == "" {
		return errors.New("hypothesis is required")
	}
	if args.Stack != "go-agent" && args.Stack != "go-web" {
		return fmt.Errorf("stack must be go-agent or go-web, got %q", args.Stack)
	}
	return nil
}

func templateFor(stack string) string {
	switch stack {
	case "go-agent":
		return "template-go-agent"
	default:
		return "template-go-web"
	}
}

func isConflict(err error) bool {
	var me *mcpclient.Error
	if errors.As(err, &me) && me.Code == -32003 {
		return true
	}
	return false
}

func marshalResult(r createResult) (json.RawMessage, error) {
	b, err := json.Marshal(r)
	if err != nil {
		return nil, fmt.Errorf("marshal result: %w", err)
	}
	return b, nil
}

func marshalPartial(r createResult, step string, inner error) (json.RawMessage, error) {
	r.FailedStep = step
	b, _ := json.Marshal(r)
	return b, fmt.Errorf("project_create step %q failed: %w", step, inner)
}