"""Progress tracker - persists chunk status across sessions."""

import json
from dataclasses import asdict
from pathlib import Path

from .decomposer import TaskChunk

TRACKER_DIR = ".claude-chunks"


def get_project_dir(project_root: Path) -> Path:
    d = project_root / TRACKER_DIR
    d.mkdir(exist_ok=True)
    return d


def save_plan(project_root: Path, task: str, chunks: list[TaskChunk], codebase_summary: str) -> Path:
    """Save a decomposed plan to disk."""
    d = get_project_dir(project_root)
    plan = {
        "task": task,
        "codebase_summary": codebase_summary,
        "chunks": [asdict(c) for c in chunks],
    }
    plan_file = d / "plan.json"
    plan_file.write_text(json.dumps(plan, indent=2))

    # Also write individual prompt files for easy copy-paste
    prompts_dir = d / "prompts"
    prompts_dir.mkdir(exist_ok=True)
    for chunk in chunks:
        prompt_file = prompts_dir / f"chunk_{chunk.id:02d}.md"
        prompt_file.write_text(chunk.prompt(codebase_summary, len(chunks)))

    return plan_file


def load_plan(project_root: Path) -> dict | None:
    """Load an existing plan from disk."""
    plan_file = project_root / TRACKER_DIR / "plan.json"
    if not plan_file.exists():
        return None
    return json.loads(plan_file.read_text())


def mark_done(project_root: Path, chunk_id: int) -> bool:
    """Mark a chunk as completed."""
    plan = load_plan(project_root)
    if not plan:
        return False

    for chunk in plan["chunks"]:
        if chunk["id"] == chunk_id:
            chunk["status"] = "done"
            plan_file = project_root / TRACKER_DIR / "plan.json"
            plan_file.write_text(json.dumps(plan, indent=2))
            return True
    return False


def get_next_chunk(project_root: Path) -> dict | None:
    """Get the next pending chunk whose dependencies are satisfied."""
    plan = load_plan(project_root)
    if not plan:
        return None

    done_ids = {c["id"] for c in plan["chunks"] if c["status"] == "done"}

    for chunk in plan["chunks"]:
        if chunk["status"] != "pending":
            continue
        deps = set(chunk.get("depends_on", []))
        if deps.issubset(done_ids):
            return chunk
    return None


def get_status_summary(project_root: Path) -> str:
    """Get a human-readable status summary."""
    plan = load_plan(project_root)
    if not plan:
        return "No active plan found. Run `ctc plan` first."

    chunks = plan["chunks"]
    done = sum(1 for c in chunks if c["status"] == "done")
    total = len(chunks)
    task = plan["task"]

    lines = [
        f"Task: {task}",
        f"Progress: {done}/{total} chunks complete",
        "",
    ]

    for c in chunks:
        status_icon = {"done": "[x]", "pending": "[ ]", "skipped": "[-]"}.get(c["status"], "[ ]")
        deps = ""
        if c.get("depends_on"):
            deps = f" (after: {', '.join(str(d) for d in c['depends_on'])})"
        lines.append(f"  {status_icon} {c['id']}. {c['title']}{deps}")

    if done < total:
        nxt = get_next_chunk(project_root)
        if nxt:
            lines.extend(["", f"Next up: Chunk {nxt['id']} - {nxt['title']}",
                          f"  Prompt file: {TRACKER_DIR}/prompts/chunk_{nxt['id']:02d}.md"])

    return "\n".join(lines)