import { mkdirSync, writeFileSync } from "node:fs"
import { join } from "node:path"
import type { ExtensionAPI, ExtensionCommandContext } from "@earendil-works/pi-coding-agent"
import { initProgress } from "./progress.ts"
import type { ChapterMeta } from "./types.ts"

/**
 * Post-onboarding project flow.
 *
 * 1. ctx.ui.input — YouTube URL
 * 2. ctx.ui.input — project name (defaults to YT video title)
 * 3. Scaffold {cwd}/{name}/chapters/
 * 4. Gemini (JSON mode) → chapter-index.md + summary.md + chapter-N.md per chapter
 */
import { Type as GType, GoogleGenAI } from "@google/genai"

// ── Types ─────────────────────────────────────────────────────────────────────

interface Chapter {
  title: string
  concepts: string[]
  duration: string
  notes: string
  keyTakeaway: string
}

interface VideoAnalysis {
  summary: string
  techstack: string
  chapters: Chapter[]
}

// ── Helpers ───────────────────────────────────────────────────────────────────

const toFolder = (s: string): string =>
  s
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "")
    .slice(0, 50)

const YT_RE = /(?:youtube\.com\/watch\?v=|youtu\.be\/)([\w-]+)/

const ytTitle = async (url: string): Promise<string> => {
  try {
    const res = await fetch(
      `https://www.youtube.com/oembed?url=${encodeURIComponent(url)}&format=json`
    )
    const data = (await res.json()) as { title?: string }
    return data.title ?? "project"
  } catch {
    return "project"
  }
}

// ── Gemini analysis ───────────────────────────────────────────────────────────

const analyzeVideo = async (url: string, name: string): Promise<VideoAnalysis> => {
  const apiKey = process.env.GEMINI_API_KEY
  if (!apiKey) throw new Error("GEMINI_API_KEY is not set")

  const ai = new GoogleGenAI({ apiKey })

  const result = await ai.models.generateContent({
    model: "gemini-3.5-flash",
    contents: [
      {
        role: "user",
        parts: [
          {
            text: `Analyze this YouTube tutorial and return structured JSON.
URL: ${url}
Project name: "${name}"

Return a JSON object matching the schema exactly. Be specific to the actual video content — no filler.

Fields:
- summary: 2–3 sentence description of what this project builds and what problem it solves — written as a project README description, not a tutorial summary. Do not mention "this tutorial" or "this video".
- techstack: a concise Markdown description of the project's tech stack (runtime, package manager, language, framework, key libraries, test runner, any important conventions). This will be injected into every chapter session so the AI tutor never needs to ask. Example: "**Runtime**: Bun\n**Package manager**: bun\n**Language**: TypeScript\n**Framework**: Hono\n**Testing**: Vitest (via bunx)\n\nAll commands use \'bun\'. Strict TypeScript throughout."
- chapters: array of chapters, each with:
  - title: short chapter title (no number prefix)
  - concepts: array of 2–5 key topics covered
  - duration: estimated time range (e.g. "0:00–8:30")
  - notes: one sentence on what the viewer builds or learns
  - keyTakeaway: single most important insight from this chapter`,
          },
        ],
      },
    ],
    config: {
      responseMimeType: "application/json",
      responseSchema: {
        type: GType.OBJECT,
        properties: {
          summary: { type: GType.STRING },
          techstack: { type: GType.STRING },
          chapters: {
            type: GType.ARRAY,
            items: {
              type: GType.OBJECT,
              properties: {
                title: { type: GType.STRING },
                concepts: { type: GType.ARRAY, items: { type: GType.STRING } },
                duration: { type: GType.STRING },
                notes: { type: GType.STRING },
                keyTakeaway: { type: GType.STRING },
              },
              required: ["title", "concepts", "duration", "notes", "keyTakeaway"],
            },
          },
        },
        required: ["summary", "techstack", "chapters"],
      },
    },
  })

  return JSON.parse(result.text ?? "{}") as VideoAnalysis
}

// ── File builders ─────────────────────────────────────────────────────────────

const buildTechstack = (techstack: string): string => techstack.trim()

const buildRoadmapJson = (name: string, analysis: VideoAnalysis): string =>
  JSON.stringify(
    {
      name,
      chapters: analysis.chapters.map((ch, i) => ({
        n: i + 1,
        title: ch.title,
        duration: ch.duration,
        done: false,
        kind: null,
      })),
    },
    null,
    2
  )

const buildSummary = (
  name: string,
  url: string,
  analysis: VideoAnalysis
): string => `# ${name} — Summary

**Source**: ${url}

${analysis.summary}

## What You'll Learn

${analysis.chapters.map((ch, i) => `- **Chapter ${i + 1}** — ${ch.title}: ${ch.keyTakeaway}`).join("\n")}

---

← [[chapter-index]]
`

const buildIndex = (name: string, url: string, analysis: VideoAnalysis): string => {
  const rows = analysis.chapters
    .map(
      (ch, i) =>
        `| [[chapter-${i + 1}\\|Chapter ${i + 1}]] | ${ch.title} | ${ch.duration} | ${ch.concepts.join(", ")} |`
    )
    .join("\n")

  return `# ${name} — Chapter Index

**Source**: ${url}

> ${analysis.summary}

[[summary|→ Full Summary]]

## Chapters

| # | Title | Duration | Key Concepts |
|---|-------|----------|--------------|
${rows}

---

*${analysis.chapters.length} chapters · generated by poiesis*
`
}

const buildChapter = (ch: Chapter, n: number, total: number): string => {
  const prev = n > 1 ? `[[chapter-${n - 1}|← Chapter ${n - 1}]]` : "[[chapter-index|← Index]]"
  const next = n < total ? `[[chapter-${n + 1}|Chapter ${n + 1} →]]` : "[[chapter-index|→ Index]]"

  return `# Chapter ${n} — ${ch.title}

**Concepts**: ${ch.concepts.join(", ")}
**Duration**: ${ch.duration}

## What You Learn

${ch.notes}

## Key Takeaway

> ${ch.keyTakeaway}

---

${prev} · ${next}
`
}

// ── Scaffold ──────────────────────────────────────────────────────────────────

const GITIGNORE = `node_modules/
dist/
.env
.env.local
*.log
.pi
.poiesis
`

const buildReadme = (name: string, url: string, analysis: VideoAnalysis): string =>
  `# ${name}\n\n${analysis.summary}\n\n---\n\n<sub>Made with help of <a href="https://shanvit7.github.io/poiesis/">Poiesis</a> watching <a href="${url}">${url}</a></sub>\n`

const scaffoldChapters = (
  chaptersDir: string,
  projectDir: string,
  name: string,
  url: string,
  analysis: VideoAnalysis
): void => {
  const write = (filename: string, content: string): void =>
    writeFileSync(join(chaptersDir, filename), content, "utf8")

  write("summary.md", buildSummary(name, url, analysis))
  write("chapter-index.md", buildIndex(name, url, analysis))
  write("techstack.md", buildTechstack(analysis.techstack))
  write("roadmap.json", buildRoadmapJson(name, analysis))

  for (let i = 0; i < analysis.chapters.length; i++) {
    write(
      `chapter-${i + 1}.md`,
      buildChapter(analysis.chapters[i], i + 1, analysis.chapters.length)
    )
  }

  writeFileSync(join(projectDir, "README.md"), buildReadme(name, url, analysis), "utf8")

  // .gitignore at project root (not inside .poiesis)
  writeFileSync(join(projectDir, ".gitignore"), GITIGNORE, "utf8")

  // initialise progress — classifyChapter refines type at runtime
  const chapters: Record<string, ChapterMeta> = {}
  for (let i = 0; i < analysis.chapters.length; i++) {
    chapters[i + 1] = { type: "code", testsFile: null, testsPass: false }
  }
  initProgress(projectDir, analysis.chapters.length, chapters)
}

// ── Entry point ───────────────────────────────────────────────────────────────

export const runProject = async (pi: ExtensionAPI, ctx: ExtensionCommandContext): Promise<void> => {
  // 1. YT URL
  const url = (await ctx.ui.input("Paste a YouTube URL")) ?? ""
  if (!YT_RE.test(url)) {
    ctx.ui.notify("Not a valid YouTube URL — try again.", "error")
    return
  }

  // 2. Project name
  const defaultTitle = await ytTitle(url)
  const input =
    (await ctx.ui.input(`Project name — press Enter to use "${defaultTitle}"`, defaultTitle)) ||
    defaultTitle
  const name = toFolder(input) || "project"

  // 3. Scaffold directory (.poiesis/chapters lives inside the project)
  const projectDir = join(ctx.cwd, name)
  const poiesisChaptersDir = join(projectDir, ".poiesis", "chapters")
  mkdirSync(poiesisChaptersDir, { recursive: true })

  // 4. Analyze + write files
  ctx.ui.setStatus("poiesis", " Analyzing video with Gemini…")
  try {
    const analysis = await analyzeVideo(url, name)
    scaffoldChapters(poiesisChaptersDir, projectDir, name, url, analysis)
    ctx.ui.setStatus("poiesis", undefined)

    // 5. Handoff — trigger the LLM to brief the user on what was created
    await pi.sendUserMessage(
      `The poiesis project "${name}" has been scaffolded at: ${projectDir}

What was created:
- ${analysis.chapters.length} chapter guide files in .poiesis/chapters/
- techstack.md (tech context injected into every chapter session)
- roadmap.json, chapter-index.md, summary.md
- README.md
- .gitignore
- .poiesis/chapters/.progress.json (tracks chapter progress)

Tell the user all of the following:
1. The project is ready at \`${projectDir}\`
2. How to start: \`cd ${projectDir}\` then run \`/poiesis\`
3. One-line teaser of chapter 1: "${analysis.chapters[0]?.title ?? "Chapter 1"}"

Be concise — 3–4 sentences max.`
    )
  } catch (err) {
    ctx.ui.setStatus("poiesis", undefined)
    ctx.ui.notify(`Gemini error: ${String(err)}`, "error")
  }
}