package cmd

import (
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/fatih/color"
	"github.com/spf13/cobra"
	"gmgauthier.com/grokkit/config"
	"gmgauthier.com/grokkit/internal/git"
)

var changelogCmd = &cobra.Command{
	Use:   "changelog",
	Short: "Generate CHANGELOG.md section from git history for Gitea releases",
	Long:  `AI-generated changelog using only Added/Changed/Fixed. Designed so the output can be pasted directly into Gitea release notes.`,
	Run:   runChangelog,
}

func init() {
	changelogCmd.Flags().String("since", "", "Start from this tag/ref (default: previous tag)")
	changelogCmd.Flags().StringP("version", "v", "", "Override version for header (default: latest git tag)")
	changelogCmd.Flags().Bool("stdout", false, "Print ONLY the new section (ideal for Gitea release notes)")
	changelogCmd.Flags().Bool("commit", false, "After writing, remind to run grokkit commit")
	rootCmd.AddCommand(changelogCmd)
}

func runChangelog(cmd *cobra.Command, args []string) {
	stdout, _ := cmd.Flags().GetBool("stdout")
	doCommit, _ := cmd.Flags().GetBool("commit")
	version, _ := cmd.Flags().GetString("version")
	since, _ := cmd.Flags().GetString("since")

	if !git.IsRepo() {
		color.Red("Not inside a git repository")
		return
	}

	// Version from tag you set (or override)
	if version == "" {
		var err error
		version, err = git.LatestTag()
		if err != nil {
			color.Red("No git tags found. Create one first: git tag vX.Y.Z")
			return
		}
	}

	// Since ref (defaults to previous tag)
	if since == "" {
		if prev, err := git.PreviousTag(version); err == nil {
			since = prev
		} else {
			since = "HEAD~100" // safe first-release fallback
		}
	}

	logOutput, err := git.LogSince(since)
	if err != nil || strings.TrimSpace(logOutput) == "" {
		color.Yellow("No new commits since last tag.")
		return
	}

	// Grok generation (strong prompt for your exact format)
	client := newGrokClient()
	messages := buildChangelogMessages(logOutput, version)
	model := config.GetModel("changelog", "")

	color.Yellow("Asking Grok to categorize changes...")
	section := client.Stream(messages, model)

	date := time.Now().Format("2006-01-02")
	newSection := fmt.Sprintf("## [%s] - %s\n\n%s\n", version, date, section)

	if stdout {
		fmt.Print(newSection)
		return
	}

	// Build full file (prepend or create)
	content := buildFullChangelog(newSection)

	// Preview + safety confirm (exactly like commit/review)
	color.Cyan("\n--- Proposed CHANGELOG.md update ---\n%s\n--------------------------------", content)
	var confirm string
	color.Yellow("Write this to CHANGELOG.md? (y/n): ")
	_, _ = fmt.Scanln(&confirm) // we don't care about scan errors here

	if confirm != "y" && confirm != "Y" {
		color.Yellow("Aborted.")
		return
	}

	if err := os.WriteFile("CHANGELOG.md", []byte(content), 0644); err != nil {
		color.Red("Failed to write CHANGELOG.md")
		return
	}

	color.Green("✅ CHANGELOG.md updated with version %s", version)

	if doCommit {
		color.Yellow("Run `grokkit commit` (or `git add CHANGELOG.md && git commit`) to stage it.")
	}
}

func buildChangelogMessages(log, version string) []map[string]string {
	return []map[string]string{
		{
			"role": "system",
			"content": `You are an expert technical writer.
Generate a changelog section using **only** these headings (include only if content exists):
### Added
### Changed
### Fixed

Rules:
- Start directly with the section headings (no extra header — we add it).
- One optional short summary sentence at the very top (light humour OK here only).
- Every bullet must be factual, imperative, one clear action per line.
- Be concise. No marketing language or explanations.
Output ONLY clean markdown.`,
		},
		{
			"role":    "user",
			"content": fmt.Sprintf("Version: %s\n\nCommit history:\n%s", version, log),
		},
	}
}

func buildFullChangelog(newSection string) string {
	existing, err := os.ReadFile("CHANGELOG.md")
	if err != nil {
		// File doesn't exist (or unreadable) → create a new changelog with a header
		return `# Changelog

All notable changes to this project will be documented in this file.

` + newSection
	}
	return newSection + string(existing)
}