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use anchor_lang::{prelude::*, solana_program::instruction::Instruction, InstructionData};
use anchor_spl::token::{transfer, Token, TokenAccount, Transfer};
use sablier_utils::thread::ThreadResponse;

use crate::{constants::*, errors::*, state::*};

#[derive(Accounts)]
pub struct UnstakeProcess<'info> {
    pub authority: SystemAccount<'info>,

    #[account(
        mut,
        associated_token::authority = delegation.authority,
        associated_token::mint = config.load()?.mint,
    )]
    pub authority_tokens: Account<'info, TokenAccount>,

    #[account(address = Config::pubkey())]
    pub config: AccountLoader<'info, Config>,

    #[account(
        mut,
        seeds = [
            SEED_DELEGATION,
            delegation.worker.as_ref(),
            delegation.id.to_be_bytes().as_ref(),
        ],
        bump,
        has_one = authority,
        has_one = worker,
    )]
    pub delegation: Account<'info, Delegation>,

    #[account(
        mut,
        seeds = [SEED_REGISTRY],
        bump,
    )]
    pub registry: Account<'info, Registry>,

    #[account(address = config.load()?.epoch_thread)]
    pub thread: Signer<'info>,

    pub token_program: Program<'info, Token>,

    #[account(
        mut,
        seeds = [
            SEED_UNSTAKE,
            unstake.id.to_be_bytes().as_ref(),
        ],
        bump,
        has_one = authority,
        has_one = delegation
    )]
    pub unstake: Account<'info, Unstake>,

    #[account(address = worker.pubkey())]
    pub worker: Account<'info, Worker>,

    #[account(
        mut,
        associated_token::authority = worker,
        associated_token::mint = config.load()?.mint,
    )]
    pub worker_tokens: Account<'info, TokenAccount>,
}

pub fn handler(ctx: Context<UnstakeProcess>) -> Result<ThreadResponse> {
    // Get accounts.
    let authority = &ctx.accounts.authority;
    let authority_tokens = &ctx.accounts.authority_tokens;
    let config = &ctx.accounts.config;
    let delegation = &mut ctx.accounts.delegation;
    let registry = &mut ctx.accounts.registry;
    let thread = &ctx.accounts.thread;
    let token_program = &ctx.accounts.token_program;
    let unstake = &ctx.accounts.unstake;
    let worker = &ctx.accounts.worker;
    let worker_tokens = &ctx.accounts.worker_tokens;

    // Verify the unstake amount is valid.
    require!(
        unstake.amount <= delegation.stake_amount,
        SablierError::InvalidUnstakeAmount
    );

    // Transfer tokens from the worker to the authority.
    transfer(
        CpiContext::new_with_signer(
            token_program.to_account_info(),
            Transfer {
                from: worker_tokens.to_account_info(),
                to: authority_tokens.to_account_info(),
                authority: worker.to_account_info(),
            },
            &[&[SEED_WORKER, worker.id.to_be_bytes().as_ref()]],
        ),
        unstake.amount,
    )?;

    // Decrement the delegations locked stake balacne by the requested unstake amount.
    delegation.stake_amount -= unstake.amount;

    // Close the unstake account by transfering all lamports to the authority.
    let balance = unstake.get_lamports();
    unstake.sub_lamports(balance)?;
    authority.add_lamports(balance)?;

    // If this is the last unstake, then reset the registry's unstake counter.
    if (unstake.id + 1) == registry.total_unstakes {
        registry.total_unstakes = 0;
    }

    // Build next instruction for the thread.
    let dynamic_instruction = if (unstake.id + 1) < registry.total_unstakes {
        let next_unstake_pubkey = Unstake::pubkey(unstake.id + 1);
        Some(
            Instruction {
                program_id: crate::ID,
                accounts: crate::accounts::UnstakePreprocess {
                    config: config.key(),
                    registry: registry.key(),
                    thread: thread.key(),
                    unstake: next_unstake_pubkey,
                }
                .to_account_metas(Some(true)),
                data: crate::instruction::UnstakePreprocess {}.data(),
            }
            .into(),
        )
    } else {
        None
    };

    Ok(ThreadResponse {
        dynamic_instruction,
        close_to: None,
        trigger: None,
    })
}