//! Pure wizard state machine helpers — no I/O, no side effects.
//!
//! All functions here take data (strings, booleans, enum values), never paths.
//! Filesystem probes belong in `io.rs`; orchestration in `mod.rs`.
//! These functions are unit-testable without tempdirs or async runtimes.

use crate::io::wizard::WizardStep;
use std::path::{Path, PathBuf};

/// Project build-tool detection flags produced by `io::detect_project_tools`.
pub(crate) struct ProjectTools {
    pub has_cargo: bool,
    pub has_pkg: bool,
    pub has_pnpm: bool,
    pub has_frontend_subdir: bool,
    pub has_go: bool,
    pub has_python: bool,
}

/// Return true when the directory contains no meaningful source files.
///
/// A "bare" project has only huskies scaffolding — no code, build manifests,
/// or source directories. Takes a slice of filename strings so it can be
/// called without touching the filesystem.
pub(crate) fn is_bare_project(file_names: &[impl AsRef<str>]) -> bool {
    file_names.iter().all(|n| {
        let n = n.as_ref();
        n.starts_with('.')
            || n == "CLAUDE.md"
            || n == "LICENSE"
            || n == "README.md"
            || n == "script"
    })
}

/// Return true when `step` produces a script file that must be made executable.
pub(crate) fn is_script_step(step: WizardStep) -> bool {
    matches!(
        step,
        WizardStep::TestScript
            | WizardStep::BuildScript
            | WizardStep::LintScript
            | WizardStep::ReleaseScript
            | WizardStep::TestCoverage
    )
}

/// Serialise a `WizardStep` to its snake_case slug (e.g. `"test_script"`).
pub(crate) fn step_slug(step: WizardStep) -> String {
    serde_json::to_value(step)
        .ok()
        .and_then(|v| v.as_str().map(String::from))
        .unwrap_or_default()
}

/// Return the output path for a step relative to `project_root`.
///
/// Pure path concatenation — no filesystem access. Returns `None` for
/// `Scaffold` which has no single output file.
pub(crate) fn step_output_path(project_root: &Path, step: WizardStep) -> Option<PathBuf> {
    match step {
        WizardStep::Context => Some(
            project_root
                .join(".huskies")
                .join("specs")
                .join("00_CONTEXT.md"),
        ),
        WizardStep::Stack => Some(
            project_root
                .join(".huskies")
                .join("specs")
                .join("tech")
                .join("STACK.md"),
        ),
        WizardStep::TestScript => Some(project_root.join("script").join("test")),
        WizardStep::BuildScript => Some(project_root.join("script").join("build")),
        WizardStep::LintScript => Some(project_root.join("script").join("lint")),
        WizardStep::ReleaseScript => Some(project_root.join("script").join("release")),
        WizardStep::TestCoverage => Some(project_root.join("script").join("test_coverage")),
        WizardStep::Scaffold => None,
    }
}

/// Generate an agent hint for a wizard step.
///
/// `is_bare` — true when the project has no source files beyond scaffolding.
/// `tools` — detected build system presence (no filesystem access needed here).
pub(crate) fn generation_hint(step: WizardStep, is_bare: bool, tools: &ProjectTools) -> String {
    match step {
        WizardStep::Context => {
            if is_bare {
                "This is a bare project with no existing code. Ask the user what they want \
                 to build — the project's purpose, goals, target users, and key features. \
                 Then generate `.huskies/specs/00_CONTEXT.md` from their answers covering:\n\
                 - High-level goal of the project\n\
                 - Core features\n\
                 - Domain concepts and entities\n\
                 - Glossary of abbreviations and technical terms"
                    .to_string()
            } else {
                "Read the project source tree and generate a `.huskies/specs/00_CONTEXT.md` describing:\n\
                 - High-level goal of the project\n\
                 - Core features\n\
                 - Domain concepts and entities\n\
                 - Glossary of abbreviations and technical terms"
                    .to_string()
            }
        }
        WizardStep::Stack => {
            if is_bare {
                "This is a bare project with no existing code. Ask the user what language, \
                 frameworks, and tools they plan to use. Then generate `.huskies/specs/tech/STACK.md` \
                 from their answers covering:\n\
                 - Language, frameworks, and runtimes\n\
                 - Coding standards and linting rules\n\
                 - Quality gates (commands that must pass before merging)\n\
                 - Approved libraries and their purpose"
                    .to_string()
            } else {
                "Read the project source tree and generate a `.huskies/specs/tech/STACK.md` describing:\n\
                 - Language, frameworks, and runtimes\n\
                 - Coding standards and linting rules\n\
                 - Quality gates (commands that must pass before merging)\n\
                 - Approved libraries and their purpose"
                    .to_string()
            }
        }
        WizardStep::TestScript => {
            if is_bare {
                "This is a bare project with no existing code. Read the STACK.md generated \
                 in the previous step (or ask the user about their stack if it was skipped) \
                 and generate a `script/test` shell script (#!/usr/bin/env bash, set -euo pipefail) \
                 with appropriate test commands for their chosen language and framework."
                    .to_string()
            } else {
                let mut cmds = Vec::new();
                if tools.has_cargo {
                    cmds.push("cargo nextest run");
                }
                if tools.has_pkg {
                    cmds.push(if tools.has_pnpm {
                        "pnpm test"
                    } else {
                        "npm test"
                    });
                }
                if cmds.is_empty() {
                    "Generate a `script/test` shell script (#!/usr/bin/env bash, set -euo pipefail) that runs the project's test suite.".to_string()
                } else {
                    format!(
                        "Generate a `script/test` shell script (#!/usr/bin/env bash, set -euo pipefail) that runs: {}",
                        cmds.join(", ")
                    )
                }
            }
        }
        WizardStep::BuildScript => {
            if is_bare {
                "This is a bare project with no existing code. Read the STACK.md generated \
                 in the previous step (or ask the user about their stack if it was skipped) \
                 and generate a `script/build` shell script (#!/usr/bin/env bash, set -euo pipefail) \
                 with appropriate build commands for their chosen language and framework."
                    .to_string()
            } else {
                let mut cmds = Vec::new();
                if tools.has_cargo {
                    cmds.push("cargo build --release");
                }
                if tools.has_pkg {
                    cmds.push(if tools.has_pnpm {
                        "pnpm run build"
                    } else {
                        "npm run build"
                    });
                }
                if tools.has_frontend_subdir {
                    cmds.push("(cd frontend && npm run build)");
                }
                if tools.has_go {
                    cmds.push("go build ./...");
                }
                if cmds.is_empty() {
                    "Generate a `script/build` shell script (#!/usr/bin/env bash, set -euo pipefail) that builds the project.".to_string()
                } else {
                    format!(
                        "Generate a `script/build` shell script (#!/usr/bin/env bash, set -euo pipefail) that runs: {}",
                        cmds.join(", ")
                    )
                }
            }
        }
        WizardStep::LintScript => {
            if is_bare {
                "This is a bare project with no existing code. Read the STACK.md generated \
                 in the previous step (or ask the user about their stack if it was skipped) \
                 and generate a `script/lint` shell script (#!/usr/bin/env bash, set -euo pipefail) \
                 with appropriate lint commands for their chosen language and framework."
                    .to_string()
            } else {
                let mut cmds = Vec::new();
                if tools.has_cargo {
                    cmds.push("cargo fmt --all --check");
                    cmds.push("cargo clippy -- -D warnings");
                }
                if tools.has_pkg {
                    cmds.push(if tools.has_pnpm {
                        "pnpm run lint"
                    } else {
                        "npm run lint"
                    });
                }
                if tools.has_python {
                    cmds.push("flake8 . (or ruff check . if ruff is configured)");
                }
                if tools.has_go {
                    cmds.push("go vet ./...");
                }
                if cmds.is_empty() {
                    "Generate a `script/lint` shell script (#!/usr/bin/env bash, set -euo pipefail) that runs the project's linters.".to_string()
                } else {
                    format!(
                        "Generate a `script/lint` shell script (#!/usr/bin/env bash, set -euo pipefail) that runs: {}",
                        cmds.join(", ")
                    )
                }
            }
        }
        WizardStep::ReleaseScript => {
            if is_bare {
                "This is a bare project with no existing code. Read the STACK.md generated \
                 in the previous step (or ask the user about their stack if it was skipped) \
                 and generate a `script/release` shell script (#!/usr/bin/env bash, set -euo pipefail) \
                 with appropriate build/release commands for their chosen language and framework."
                    .to_string()
            } else {
                "Generate a `script/release` shell script (#!/usr/bin/env bash, set -euo pipefail) that builds and releases the project (e.g. `cargo build --release` or `npm run build`).".to_string()
            }
        }
        WizardStep::TestCoverage => {
            if is_bare {
                "This is a bare project with no existing code. Read the STACK.md generated \
                 in the previous step (or ask the user about their stack if it was skipped) \
                 and generate a `script/test_coverage` shell script (#!/usr/bin/env bash, set -euo pipefail) \
                 with appropriate test coverage commands for their chosen language and framework."
                    .to_string()
            } else {
                "Generate a `script/test_coverage` shell script (#!/usr/bin/env bash, set -euo pipefail) that generates a test coverage report (e.g. `cargo llvm-cov nextest` or `npm run coverage`).".to_string()
            }
        }
        WizardStep::Scaffold => {
            "Scaffold step is handled automatically by `huskies init`.".to_string()
        }
    }
}

// ── tests ─────────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;

    fn no_tools() -> ProjectTools {
        ProjectTools {
            has_cargo: false,
            has_pkg: false,
            has_pnpm: false,
            has_frontend_subdir: false,
            has_go: false,
            has_python: false,
        }
    }

    fn cargo_tools() -> ProjectTools {
        ProjectTools {
            has_cargo: true,
            ..no_tools()
        }
    }

    #[test]
    fn is_bare_project_empty_dir() {
        let names: Vec<&str> = vec![];
        assert!(is_bare_project(&names));
    }

    #[test]
    fn is_bare_project_scaffold_only() {
        let names = [".huskies", "CLAUDE.md", "README.md", "script", ".git"];
        assert!(is_bare_project(&names));
    }

    #[test]
    fn is_bare_project_false_with_cargo_toml() {
        let names = [".huskies", "Cargo.toml"];
        assert!(!is_bare_project(&names));
    }

    #[test]
    fn is_bare_project_false_with_src_dir() {
        let names = ["src"];
        assert!(!is_bare_project(&names));
    }

    #[test]
    fn is_script_step_includes_all_scripts() {
        assert!(is_script_step(WizardStep::TestScript));
        assert!(is_script_step(WizardStep::BuildScript));
        assert!(is_script_step(WizardStep::LintScript));
        assert!(is_script_step(WizardStep::ReleaseScript));
        assert!(is_script_step(WizardStep::TestCoverage));
    }

    #[test]
    fn is_script_step_excludes_non_scripts() {
        assert!(!is_script_step(WizardStep::Scaffold));
        assert!(!is_script_step(WizardStep::Context));
        assert!(!is_script_step(WizardStep::Stack));
    }

    #[test]
    fn step_slug_context() {
        assert_eq!(step_slug(WizardStep::Context), "context");
    }

    #[test]
    fn step_slug_test_script() {
        assert_eq!(step_slug(WizardStep::TestScript), "test_script");
    }

    #[test]
    fn step_slug_scaffold() {
        assert_eq!(step_slug(WizardStep::Scaffold), "scaffold");
    }

    #[test]
    fn step_output_path_context() {
        let p = step_output_path(Path::new("/proj"), WizardStep::Context).unwrap();
        assert!(p.ends_with(".huskies/specs/00_CONTEXT.md"));
    }

    #[test]
    fn step_output_path_build_script() {
        let p = step_output_path(Path::new("/proj"), WizardStep::BuildScript).unwrap();
        assert!(p.ends_with("script/build"));
    }

    #[test]
    fn step_output_path_lint_script() {
        let p = step_output_path(Path::new("/proj"), WizardStep::LintScript).unwrap();
        assert!(p.ends_with("script/lint"));
    }

    #[test]
    fn step_output_path_scaffold_is_none() {
        assert!(step_output_path(Path::new("/proj"), WizardStep::Scaffold).is_none());
    }

    #[test]
    fn generation_hint_bare_context_asks_user() {
        let hint = generation_hint(WizardStep::Context, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("Ask the user"));
    }

    #[test]
    fn generation_hint_bare_stack_asks_user() {
        let hint = generation_hint(WizardStep::Stack, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("Ask the user"));
    }

    #[test]
    fn generation_hint_bare_test_script_references_stack() {
        let hint = generation_hint(WizardStep::TestScript, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("STACK.md"));
    }

    #[test]
    fn generation_hint_bare_build_script_references_stack() {
        let hint = generation_hint(WizardStep::BuildScript, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("STACK.md"));
    }

    #[test]
    fn generation_hint_bare_lint_script_references_stack() {
        let hint = generation_hint(WizardStep::LintScript, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("STACK.md"));
    }

    #[test]
    fn generation_hint_bare_release_script_references_stack() {
        let hint = generation_hint(WizardStep::ReleaseScript, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("STACK.md"));
    }

    #[test]
    fn generation_hint_bare_test_coverage_references_stack() {
        let hint = generation_hint(WizardStep::TestCoverage, true, &no_tools());
        assert!(hint.contains("bare project"));
        assert!(hint.contains("STACK.md"));
    }

    #[test]
    fn generation_hint_existing_context_reads_code() {
        let hint = generation_hint(WizardStep::Context, false, &cargo_tools());
        assert!(hint.contains("Read the project"));
        assert!(!hint.contains("bare project"));
    }

    #[test]
    fn generation_hint_existing_test_script_detects_cargo() {
        let hint = generation_hint(WizardStep::TestScript, false, &cargo_tools());
        assert!(hint.contains("cargo nextest"));
        assert!(!hint.contains("bare project"));
    }

    #[test]
    fn generation_hint_existing_build_script_detects_cargo() {
        let hint = generation_hint(WizardStep::BuildScript, false, &cargo_tools());
        assert!(hint.contains("cargo build --release"));
        assert!(!hint.contains("bare project"));
    }

    #[test]
    fn generation_hint_existing_lint_script_detects_cargo() {
        let hint = generation_hint(WizardStep::LintScript, false, &cargo_tools());
        assert!(hint.contains("cargo fmt --all --check"));
        assert!(hint.contains("cargo clippy -- -D warnings"));
        assert!(!hint.contains("bare project"));
    }
}
