#!/bin/bash
# PreCompact Hook - Extract and preserve critical context before conversation compaction
# Ensures important state survives context window compression
#
# Input: JSON (unused, but read for consistency)
# Output: JSON with systemMessage containing preserved context
#
# Timeout: 10 seconds - keep operations lightweight

set -euo pipefail

# Read input from stdin (for consistency with other hooks)
input=$(cat)

# Get project directory
PROJECT_DIR="${CLAUDE_PROJECT_DIR:-$(pwd)}"

# Quick exit if not a valid directory
if [[ ! -d "$PROJECT_DIR" ]]; then
    echo '{"continue": true}'
    exit 0
fi

# =============================================================================
# GATHER CONTEXT TO PRESERVE
# =============================================================================

PRESERVED_PARTS=()

# --- Current Task Detection ---
CURRENT_TASK=""

# Check Claude's task tracking first (most authoritative)
if [[ -f "$PROJECT_DIR/.claude/tasks.json" ]]; then
    # Get in-progress tasks (highest priority)
    IN_PROGRESS=$(jq -r '[.[] | select(.status == "in_progress")] | .[0].subject // empty' "$PROJECT_DIR/.claude/tasks.json" 2>/dev/null || echo "")
    if [[ -n "$IN_PROGRESS" ]]; then
        CURRENT_TASK="$IN_PROGRESS"
    else
        # Fall back to first pending task
        PENDING=$(jq -r '[.[] | select(.status == "pending")] | .[0].subject // empty' "$PROJECT_DIR/.claude/tasks.json" 2>/dev/null || echo "")
        if [[ -n "$PENDING" ]]; then
            CURRENT_TASK="$PENDING"
        fi
    fi
fi

# Check for TODO files if no Claude task found
if [[ -z "$CURRENT_TASK" ]]; then
    for todofile in TODO.md TODO.txt todo.md todo.txt; do
        if [[ -f "$PROJECT_DIR/$todofile" ]]; then
            # Get first unchecked item
            FIRST_TODO=$(grep -m1 '^\s*-\s*\[ \]' "$PROJECT_DIR/$todofile" 2>/dev/null | sed 's/^\s*-\s*\[ \]\s*//' || echo "")
            if [[ -n "$FIRST_TODO" ]]; then
                CURRENT_TASK="$FIRST_TODO"
                break
            fi
        fi
    done
fi

if [[ -n "$CURRENT_TASK" ]]; then
    PRESERVED_PARTS+=("**Current Task:** $CURRENT_TASK")
fi

# --- Files Being Modified (from git status) ---
MODIFIED_FILES=""
if [[ -d "$PROJECT_DIR/.git" ]]; then
    # Get modified files (staged and unstaged) - limit to 10 for brevity
    MODIFIED=$(git -C "$PROJECT_DIR" status --porcelain 2>/dev/null | head -10 | awk '{print $2}' | tr '\n' ', ' | sed 's/,$//')
    if [[ -n "$MODIFIED" ]]; then
        MODIFIED_FILES="$MODIFIED"
        # Count total if more than 10
        TOTAL_MODIFIED=$(git -C "$PROJECT_DIR" status --porcelain 2>/dev/null | wc -l | tr -d ' ')
        if [[ "$TOTAL_MODIFIED" -gt 10 ]]; then
            MODIFIED_FILES="$MODIFIED_FILES (and $((TOTAL_MODIFIED - 10)) more)"
        fi
    fi
fi

if [[ -n "$MODIFIED_FILES" ]]; then
    PRESERVED_PARTS+=("**Files Modified:** $MODIFIED_FILES")
fi

# --- Git Branch Context ---
if [[ -d "$PROJECT_DIR/.git" ]]; then
    GIT_BRANCH=$(git -C "$PROJECT_DIR" branch --show-current 2>/dev/null || echo "")
    if [[ -n "$GIT_BRANCH" ]]; then
        PRESERVED_PARTS+=("**Branch:** \`$GIT_BRANCH\`")
    fi
fi

# --- Recent Commits (to understand context of current work) ---
if [[ -d "$PROJECT_DIR/.git" ]]; then
    # Get last 3 commit messages (one-line each)
    RECENT_COMMITS=$(git -C "$PROJECT_DIR" log -3 --oneline 2>/dev/null | awk '{$1=""; print substr($0,2)}' | tr '\n' '; ' | sed 's/; $//')
    if [[ -n "$RECENT_COMMITS" ]]; then
        PRESERVED_PARTS+=("**Recent Commits:** $RECENT_COMMITS")
    fi
fi

# --- Check for Blockers (common patterns in task files) ---
BLOCKERS=""

# Check .claude/tasks.json for blocked tasks
if [[ -f "$PROJECT_DIR/.claude/tasks.json" ]]; then
    BLOCKED_TASKS=$(jq -r '[.[] | select(.blockedBy != null and (.blockedBy | length > 0))] | .[0:3] | .[].subject // empty' "$PROJECT_DIR/.claude/tasks.json" 2>/dev/null | tr '\n' '; ' | sed 's/; $//' || echo "")
    if [[ -n "$BLOCKED_TASKS" ]]; then
        BLOCKERS="Blocked tasks: $BLOCKED_TASKS"
    fi
fi

# Check TODO files for blocked items
if [[ -z "$BLOCKERS" ]]; then
    for todofile in TODO.md TODO.txt todo.md todo.txt; do
        if [[ -f "$PROJECT_DIR/$todofile" ]]; then
            # Look for items marked blocked, waiting, or with BLOCKED/WAIT tags
            BLOCKED_ITEM=$(grep -im1 '\(blocked\|waiting\|BLOCKED\|WAIT\)' "$PROJECT_DIR/$todofile" 2>/dev/null | head -1 || echo "")
            if [[ -n "$BLOCKED_ITEM" ]]; then
                BLOCKERS="$BLOCKED_ITEM"
                break
            fi
        fi
    done
fi

if [[ -n "$BLOCKERS" ]]; then
    PRESERVED_PARTS+=("**Blockers:** $BLOCKERS")
fi

# --- Key Decisions ---
DECISIONS=""

# Check for dedicated decision files
for decfile in DECISIONS.md .claude/decisions.md decisions.md .decisions.md; do
    if [[ -f "$PROJECT_DIR/$decfile" ]]; then
        # Get last 5 non-empty lines that look like decisions (exclude headers)
        RECENT_DECISIONS=$(grep -v '^#\|^$\|^---' "$PROJECT_DIR/$decfile" 2>/dev/null | tail -5 | tr '\n' '; ' | sed 's/; $//')
        if [[ -n "$RECENT_DECISIONS" ]]; then
            DECISIONS="From $decfile: $RECENT_DECISIONS"
            break
        fi
    fi
done

# If no decision file, scan recent commit messages for decision keywords
if [[ -z "$DECISIONS" ]] && [[ -d "$PROJECT_DIR/.git" ]]; then
    # Look for commits with decision-related keywords in last 10 commits
    DECISION_COMMITS=$(git -C "$PROJECT_DIR" log -10 --oneline --grep="decided\|chose\|selected\|switched to\|went with\|picking\|opting for" -i 2>/dev/null | head -3 | awk '{$1=""; print substr($0,2)}' | tr '\n' '; ' | sed 's/; $//')
    if [[ -n "$DECISION_COMMITS" ]]; then
        DECISIONS="From commits: $DECISION_COMMITS"
    fi
fi

# Check TODO files for decided/done items (recently resolved decisions)
if [[ -z "$DECISIONS" ]]; then
    for todofile in TODO.md TODO.txt todo.md todo.txt; do
        if [[ -f "$PROJECT_DIR/$todofile" ]]; then
            # Look for checked/done items that might indicate decisions
            DECIDED_ITEMS=$(grep -E '^\s*-\s*\[x\]|^DONE:|^DECIDED:' "$PROJECT_DIR/$todofile" 2>/dev/null | tail -3 | sed 's/^\s*-\s*\[x\]\s*//' | tr '\n' '; ' | sed 's/; $//' || echo "")
            if [[ -n "$DECIDED_ITEMS" ]]; then
                DECISIONS="Resolved: $DECIDED_ITEMS"
                break
            fi
        fi
    done
fi

if [[ -n "$DECISIONS" ]]; then
    PRESERVED_PARTS+=("**Key Decisions:** $DECISIONS")
fi

# --- Project Type (for context) ---
PROJECT_TYPE=""
if [[ -f "$PROJECT_DIR/go.mod" ]]; then
    PROJECT_TYPE="Go"
elif [[ -f "$PROJECT_DIR/package.json" ]]; then
    PROJECT_TYPE="Node.js"
elif [[ -f "$PROJECT_DIR/composer.json" ]]; then
    PROJECT_TYPE="PHP"
elif [[ -f "$PROJECT_DIR/Cargo.toml" ]]; then
    PROJECT_TYPE="Rust"
elif [[ -f "$PROJECT_DIR/pyproject.toml" ]] || [[ -f "$PROJECT_DIR/requirements.txt" ]]; then
    PROJECT_TYPE="Python"
fi

if [[ -n "$PROJECT_TYPE" ]]; then
    PRESERVED_PARTS+=("**Project Type:** $PROJECT_TYPE")
fi

# =============================================================================
# BUILD OUTPUT
# =============================================================================

# If nothing to preserve, allow silently
if [[ ${#PRESERVED_PARTS[@]} -eq 0 ]]; then
    echo '{"continue": true}'
    exit 0
fi

# Build the preserved context message
CONTEXT_MSG="## Preserved Context (Pre-Compaction)\\n\\n"
CONTEXT_MSG+="The following context was preserved before conversation compaction:\\n\\n"

for part in "${PRESERVED_PARTS[@]}"; do
    CONTEXT_MSG+="$part\\n"
done

CONTEXT_MSG+="\\n---\\n"
CONTEXT_MSG+="*This context was automatically preserved by the PreCompact hook.*"

# Use jq for proper JSON string escaping
ESCAPED_MSG=$(printf '%s' "$CONTEXT_MSG" | jq -sRr @json)

# Output JSON response (ESCAPED_MSG already includes quotes from jq)
cat << EOF
{
  "continue": true,
  "systemMessage": $ESCAPED_MSG
}
EOF